bluuebunny/crossref_metadata_2025 huggingface dataset:
The Current Status of Weinberg's Differential Rule
Authors: James W.H.
Published: July 2016

A reanalysis of the data presented in a recent large twin study suggests that opposite-sexed (OS) pairs may be not as exhaustively tested as same-sexed (SS) pairs on genetic markers. This is contrary to an assumption I made in estimating that there are about 8 SS dizygotic pairs to every 7 OS pairs (thus impugning Weinberg's differential rule). If this assumption is false also in regard to the samples I discussed, then that estimate is unsound and Weinberg's rule is unscathed by empirical data. However, regardless of such considerations, there are strong theoretical reasons for questioning the status of Weinberg's rule. It is based on two assumptions, namely that p (the probability that a dizygotic twin zygote is male) is equal and independent for all dizygotic twin zygotes. Data are adduced here to suggest that both assumptions are false. The upshot is that, at present, without testing, we cannot know, of any given population, whether the rule holds or not. Otherwise, though Weinberg's rule may be useful (like Hellin's law) as a rule-of-thumb, it cannot be assumed as a basis for serious scientific argument.
Similarity in General Cognitive Ability, Creativity, and Cognitive Style in a Sample of Adolescent Russian Twins
Authors: Grigorenko E.L. , LaBuda M.C. , Carter A.S.
Published: July 2016

Data on five tests of general and specific cognitive abilities, cognitive styles, and creativity, obtained from members of 60 identical and 63 fraternal Russian adolescent twin pairs, are presented. All tests are adaptations of standardized instruments widely used outside of the Soviet Union. Identical and fraternal twin correlations for general cognitive ability yielded a lower estimate of heritability (0.29) than generally found in other countries worldwide (0.52) although the twin correlations themselves are fairly comparable to figures from other countries and cultures — 0.83 and 0.69 for Russian identical and fraternal twin pairs, respectively, vs 0.86 and 0.60 for non-Russian identical, and fraternal twin pairs. Twin correlations for other cognitive-related abilities assessed were also comparable to correlations obtained outside the Soviet Union with the exception of creativity which yielded higher within-pair resemblance than reported in previous twin studies.
Zygosity, Placental Membranes and Weinberg's Rule in a Danish Consecutive Twin Series
Authors: Husby H. , Holm N.V. , Gernow A. , Thomsen S.G. , Kock K. , Gürtler H.
Published: July 2016

The usual assumption that monochorionic twins are monozygotic has recently been questioned, based on blood group discordance in 3 of 12 monochorionic pairs. Therefore, this study evaluates the validity of zygosity diagnosis based on examination of placental membranes, and at the same time evaluates Weinberg's differential rule in a Danish consecutive twin series. All twin pairs, 265 like-sexed and 87 unlike-sexed pairs, born at Odense University Hospital, Denmark, from 1 January 1980 through 31 August 1988, were ascertained. In 229 like-sexed pairs, zygosity was determined by serological methods, and in 190 of these, the fetal membranes could be reliably classified. Fiftynine monochorionic twin pairs were identified and none of those pairs were discordant for any genetic markers. Therefore, we conclude that monochorionic twins can be considered monozygotic. The distribution of monozygotic and dizygotic pairs was in accordance with Weinberg's rule.
Maternal and Child Care: The Canadian Model
Authors: Milligan J.E.
Published: July 2016

A sophisticated regionalization plan in maternal and child care, including risk assessment, maternal transfer mechanisms, 24 hour communication availability, and regional tertiary perinatal intensive care units (high risk obstetrics integrated with level III neonatal intensive care), has allowed the Province of Ontario to significantly decrease perinatal mortality. Data collection by hospital of birth, birthweight and gestational age shows that this effect is most marked in the preterm infant between 25 and 32 weeks and in hospitals with small obstetrical volumes. Little decrease in incidence of preterm birth has occurred. Multiple births provide a significant number of the preterm births; singleton rates between 20-36 weeks are 5.48%, twins 42.97%, and triplets 95.3%. However, when compared with singletons of the same birthweight, the mortality rates for twins are less than those of singletons, and triplets are even less again. High incidence of prematurity in multiple pregnancies means that a regional perinatal unit has a large occurrence of maternally transferred high risk pregnancies. In our institute, a 10-year review between 1978 and 1988, showed an incidence of 24 triplet, four quadruplet, and one quintuplet pregnancies. Review of outcome and data relative to these pregnancies showed an early neonatal mortality rate of 31.6, a perinatal mortality rate of 51.5 and survival to discharge of 93%. The occurrence of neonatal complications was respiratory distress syndrome in 43%, bronchopulmonary dysplasia in 6%, and intraventricular hemorrhage in 4%. Long term follow-up showed only one severely handicapped child (mental retardation and cerebral palsy), 10 infants with a mild hypotonia and mild delay in gross motor development (both considered functional and transient), and 74% entirely normal. It is concluded that integrated perinatal care can result in excellent outcomes for multiple pregnancies as long as all components of antenatal, intrapartum, and neonatal care are combined effectively.
Twin Studies in Auto-immune Disease
Authors: Leslie R.D.G. , Hawa M.
Published: July 2016

Immune-mediated diseases affect up to 5% of the population and are a major cause of morbidity and mortality. These diseases can be organ specific, such as insulin-dependent diabetes (IDDM) and non-organ specific, such as Rheumatoid Arthritis (RA). Identical and non-identical twins have been used to establish whether these diseases are determined by genetic or environmental factors. The results of these studies have been collated in a new section of the Mendel Institute in Rome.

Diseases included in these studies included IDDM, RA, Systemic Lupus Erythematosus (SLE), Multiple Sclerosis (MS) and Myasthenia. Striking differences in concordance rates between identical and non-identical twins in all these studies suggest that genetic factors are important in causing these diseases. All the diseases are known to be associated with HLA genes on chromosome 6 which may account for some or all of the genetic susceptibility. However, in the majority of pairs the affected twin has an unaffected co-twin. These observations suggest that non-genetically determined factors, probably environmental factors and not somatic mutations, are critical. The study of unaffected co-twins, who are at high disease-risk, has allowed the identification of changes which precede and predict the clinical disease. The immune-mediated destruction in many of these diseases is probably caused by T-lymphocytes. Twin studies have shown the importance of genetic factors in determining T-cell responses. Identical twins should, therefore, provide the perfect test bed to assess the role of T-cells in immune-mediated diseases.
An Epidemiologic Study on the Correlation between Clinical Symptomatology and Modality of Birth in Twins, 1990 to 1993
Authors: Cannatelli L. , Gitto E. , Prudente D. , Cordaro V. , Cordaro S. , Liotta C. , Barberi I.
Published: July 2016

The neonatal intensive care of twins has seen many changes over later years. In fact, major improvements in prenatal evaluation and neonatal management techniques have greatly increased the possibility of survival for infants at risk, especially those born from multiple pregnancies. Our study reports the results of a retrospective survey for the years 1990 to 1993, on the outcome of 76 twin infants (ie. 11,4% of the 661 newborns admitted to our unit over that period) correlating the clincial symptoms observed with the modality of birth.
Studio delle Modificazioni Morfo-Funzionali delle Cellule Endoteliali in Gravidanze Gemellari
Authors: Staffolani R. , Biagini G. , Pugnaloni A. , Salvolini E. , Cester N. , Romanini C.
Published: July 2016

Le gravidanze gemellari sono caratterizzate da riduzioni delle dimensioni del feto accompagnati dai corrispondenti riduzioni placentari, come precedentemente riportato. Anche modificazioni sono state evidenziate a carico degli altri annessi embrionali, mentre varie sono le problematiche non risolte. Pertanto noi abbiamo voluto valutare le caratteristiche morfofunzionali delle vene ombelcali cordonali di gemelli dicoriali confrontandoli con quelle di gravidanze normali a termine. Sono stati analizzati i cordoni ombelicali di gravidanze a termine e da una gravidanza gemellare dicoriale recisi dalla placenta subito dopo il parto. È stata utilizzata la microscopia elettronica a trasmissione (TEM) e a scansione (SEM). Per l'indagine immuno istochimica è stata impiegata la tecnica del complesso avidina-biotina perossidasi. Le cellule endoteliali sono state ottenute con il metodo di Jaffe e per gli studi di fluorescenza è stata utilizzata la sonda l-(4 trimetilaminofenil) 6 fenil-1,3,5 — esatriene (TMA-DPH).

Nei cordoni ombelicali ottenuti da gravidanze normali a termine esse presentano una completa fase di differenziamento. Abbiamo infatti osservato: 1) elementi modicamente appiattiti, 2) protrusioni citoplasmatiche, 3) vescicole di pinocitosi e citoplasmatiche, 4) aggregati di lisomi, 5) corpi di Weibel e Palade, 6) nucleo lenticolare, 7) nucleo evidente con predominante eucromatina. La tonaca media appare ricca di fibrocellule muscolari lisce ricche di filamenti di tipo contrattile. Nei gemelli le celule endoteliali appaiono globose con aspetti di attività cellulare come anche confermato dagli studi biochimici. Le cellule muscolari sottostaminali risultano assai ricche di reticolo ergastoplasmatico e con fenotipo sintetico.

In conclusione per quanto concerne il cordone ombelicale quanto da noi osservato istochimicamente ultrastrutturalmente biochimicamente pare sottolineare uno stato di minor maturità delle gravidanze gemellari rispetto ai controlli normali a termine.
Popliteal Aneurysm in Middle-Aged Identical Twins
Authors: Vigliotti G. , Franco E. , Cimino G. , Valitutti P. , Russo R. , Angrisani P. , Stabile M. , Munno A.
Published: July 2016

Familial aggregation of isolated abdominal aortic and isolated intracranial aneurysms have been described. Therefore, districtual aneurysm without a systemic genetic disease (e.g. Marfan, Ehlers Danlos etc.) can have a genetic basis. The authors are reporting on the development, in the sixth decade of life, of popliteal aneurysm in two identical twins E.U. and E.C. Zygosity was established on the basis of blood-group determinations, HLA haplotypes and cytogenetic variants. Mild clinical symptoms (intermittent claudication, calf cramps) had begun in E.C. at 21 years of age. Later, at 52 years of age, a thrombosis of the aneurysmatic sac on one side required surgical treatment. E.U. showed no clinical symptoms until the age of 60, when, within the interval of a few months, bilateral thrombosis had developed. The weight difference in the two subjects (E.C. 72 Kg, E.U. 64 Kg) may explain the difference between them as regards the age of onset of symptoms and body sides (one or both) affected. Angiographic, macroscopic and histologic aspects are documented. On surgical intervention, the aneursym was found at the biforcation of the popliteal artery, but no anomalous insertion of gas-trocnemii appeared to cause pressure on the artery leading to aneurysmatic dilatation. The aneurysmatic sac measured 2.5 cm in diameter and on histological examination, using haematoxylin-eosin and Van Gieson stain, showed fragmented elastic, collagen fibres.
Physical Growth of Japanese Twins
Authors: Ooki S. , Asaka A.
Published: July 2016

The present study aimed at clarifying the characteristics of twins' physical growth. First, 557 pairs of normal Japanese twins were analyzed according to the following three life stages: (1) intrauterine growth, (2) body weight and height from birth to 6 years, and (3) body weight and height at school age (from 6 to 11 years). The following results were obtained. 1. Intrauterine growth of twins was very different from that of singletons, especially as regards weight, so twins should be estimated by twin standards. 2. Size deficit at birth was appropriately recovered over the first 6 years. 3. No size deficit was observed by school age. Second, the similarity of bodyweight and height according to zygosity was analyzed using 605 pairs of normal Japanese twins, 427 monozygotic (MZ), 113 same-sexed dizygotic (DZ) and 65 opposite-sexed DZ pairs. The similarity between MZ and DZ pairs was almost the same at birth. However, MZ pairs became increasingly more similar with age, whereas DZ pairs became more dissimilar. This tendency was very clearly seen through early infancy, thus suggesting that genetic factors became more apparent during this life stage.
Changing Trends in Twinning
Authors: Goswami R. , Goswami H.K.
Published: July 2016

Birth statistics (on 13,887.943 births) from 11 Indian States indicate a fall in the dizygotic twinning rate and a rise in the monozygotic twinning rate over the decade between 1982 and 1991. These figures seem to reverse the trend of the period 1960-1982. One plausible explanation is offered by the age-data on mothers, which indicate that twins of different sex are more frequently born to mothers above the age of 35. Since extensive family planning measures have reduced the upper age-limit of mothers, the birth-rate of twins of different sex has also fallen. Due to the increased proportion of twins of the same sex, Weinberg's differential method will therefore report a decline in the dizygotic twinning rate, wherever the mean age of mothers has fallen (i.e. most mothers do not reproduce after the age of 35).
Birth Defects in Twins: Study in a Spanish Population
Authors: Ramos-Arroyo M.A.
Published: July 2016

The risk for specific defects among twins compared to singletons was studied using data collected by the Spanish Collaborative Study of Congenital Malformations (ECEMC). A total of 136 twins had a major and/or minor congenital defect. The overall rate of congenital defects in twins (2.37%) did not deviate significantly from the rate in singletons (2.21%). Like-sex (LS) and male-male (MM) twin pairs had a slightly higher rate of birth defects than unlike-sex (US) and female-female (FF) pairs, respectively. Defects of the central nervous system, cardiovascular system and genitourinary system were significantly more frequent in LS twins than in singletons, with relative risks of 2.8, 2.5 and 1.6, respectively. No significantly increased risk was found among US twins. Among defects of the central nervous system, the rates of anencephaly, encephalocele and hydrocephaly were significantly higher in total and LS twins; however, no significantly increased risk for spina bifida was observed when compared to singletons. MM twins were also 1.9 times more likely to have hypospadias, but the risk among males of male-female (FM) pairs was decreased.
Selection Bias in Disease-Related Twin Studies — Data on 11,154 Adult Finnish Twin Pairs from a Nationwide Panel
Authors: Romanov K. , Koskenvuo M. , Kaprio J. , Sarna S. , Heikkilä K.
Published: July 2016

The effect of migration on pairwise concordance for disease was assessed in 11,154 twin pairs of the Finnish Twin Cohort Study by comparing the pairs living in the same province to the pairs which members were living in different provinces of Finland. The cumulative incidence of psychosis and hypertension for the years 1972-1985 were analyzed. The cumulative concordance of psychosis for those MZ twin pairs living in the same province were higher than for those MZ pairs living further apart. Similar findings were found among DZ pairs for psychosis. The cumulative concordance of hypertension was only slightly higher among those MZ and DZ pairs living in the same province compared with pairs living in different provinces. These results indicate an overestimation of concordance of psychosis caused by selective migration. This bias in twin studies is likely to influence heritability estimates in a sample of limited geographical area.
Chronological Changes in Genetic Variance and Heritability of Anthropometric Characteristics Among Chinese Twin Infants
Authors: Chen C.J. , Yu M.W. , Wang C.J. , Tong S.L. , Tien M. , Lee T.Y. , Lue H.C. , Huang F.Y. , Lan C.C. , Yang K.H. , Wang H.C. , Shih H.Y. , Liu C.Y. , Chen J.S.
Published: July 2016

In order to examine the chronologic changes in genetic variance and heritability of anthropometric characteristics of Chinese infants in Taiwan, a total of 521 pairs of same-sexed twin neonates given birth in four major general teaching hospitals in Taipei City were studied. Based on the placental pattern and 12 red blood cell antigens, 428 MZ and 93 DZ twin pairs were identified and followed up to the age of one year. There was no significant genetic variance for all anthropometric characteristics adjusted for sex and gestational week before the age of six months. After adjusting for sex and gestational week, a significant genetic variance was observed at the age of six months, with heritability values of 0.51 (weight), 0.63 (head circumference), 0.77 (chest circumference), and 0.53 (arm circumference), as well as at one year, although with considerably lower heritability values. This implies that growth is dynamically determined by both genetic and environmental factors during infancy.
An Agenda for Meeting the Special Needs of Multiple Birth Families
Authors: Malmstrom P.M. , Biale R.
Published: July 2016

Over 80,000 multiple birth babies are born each year in the U.S. Their families must cope with a constellation of complex physical and psychosocial challenges, which jeopardizes their health and functioning. The demands of twin pregnancy and the parenting of twins, triplets, quadruplets, quintuplets or more puts these families at disproportionately high risk for infant mortality, birth defects, child abuse, substance abuse, financial problems and marital problems. Health and social service resources must be developed to alleviate the stresses associated with multiple birth and to empower parents to cope well. Guidelines for policies, parent education, professional training and service delivery developed for the California Department of Health Service, Maternal and Child Health Branch, are here offered for the consideration of policy makers and public health planners.
Multiple Regression Analysis of Twin Data: Etiology of Deviant Scores versus Individual Differences
Authors: DeFries J.C. , Fulker D.W.
Published: July 2016

The multiple regression analysis of twin data in which a cotwin's score is predicted from a proband's score and the coefficient of relationship (the basic model) provides a statistically powerful test of genetic etiology. When an augmented model that also contains an interaction term is fitted to the same data set, direct estimates of heritability (h2) and the proportion of variance due to shared environmental influences (c2) are obtained. A simple transformation of selected twin data prior to regression analysis facilitates direct estimates of h2g (an index of the extent to which the difference between the mean of probands and that of the unselected population is heritable) and a test of the hypothesis that the etiology of deviant scores differs from that of variation within the normal range.
Twinning Rate in Scandinavia, Germany and the Netherlands During Years of Privation
Authors: Eriksson A.W. , Bressers W.M.A. , Kostense P.J. , Pitkänen K.J. , Mielke J.H. , Jorde L.B. , Tas R.F.J. , Fellman J.O.
Published: July 2016

Twinning rates were studied in Swedes, Åland Islanders, Finns, Germans, and Dutch during years of starvation when death rates were two to three times higher than average. In contrast to the situation among some animals, this study suggests that nutrition above a certain threshold is unimportant for human reproduction, including twinning. The twinning rates for these different populations display marked temporal differences, but low values in the twinning rate are not consistently associated with periods of epidemics, famine, or similar nutritional stress. After years of privation and/or separation of spouses, a rapid “catch-up effect” can often be seen in the twinning rates, as well as marriage and birth rates. Psychoendocrine factors and interparental immunological conditions that may be involved in this phenomenon are discussed.
U.S. Regional Changes in Twinning Rates
Authors: Allen Gordon
Published: July 2016

The rise in twinning rates previously reported for U.S. between 1964 and 1987 after adjustment for maternal age and birth order occurred in each of the nine conventional geographic divisions except the Pacific States. Differences and consistencies in rank order among the divisions with respect to crude and adjusted twinning rates and other demographic parameters may hold clues to yet unidentified influences in twinning.
Conjoined Twins in Japan, 1979-1985
Authors: Imaizumi Yoko
Published: July 2016

Nation-wide data in Japan on the 112 sets of conjoined twins from fetal deaths and from postnatal deaths during 1979-1985 were analysed. Female conjoined twins accounted for 60% of cases. The incidence rate of conjoined twins remained Constant except in 1985. Overall incidence rate was 10 per million births. Maternal age effect was found in mothers over the age of 40, where the highest incidence rate was obtained. The incidence rate of conjoined twins increased with birth order. There was no seasonal variation in the time of conception.
New Case of an EEC-Like Syndrome in Twins
Authors: Schmidt M. , Salzano F.M.
Published: July 2016

A patient wrongly referred as a possible victim of thalidomide showed the three classical cardinal features of the EEC syndrome, plus severe mental retardation, an unusual finding in this condition. His twin brother was similarly affected, and died at four months of age due to complications caused by the malformations. Their normal parents were first cousins. The concordance of the manifestation in the twins and the parents' consanguinity suggest that they had the recessive form of the EEC syndrome.
Demographic Parameters and Twinning: A Study in Catalonia, Spain
Authors: Bertranpetit J. , Marin A.
Published: July 2016

Twinning rates for the years 1975-79 in Catalonia (Spain) are presented. Crude rates are very low: 7.62 per 1,000 maternities, the DZTR and the MZTR being 3.74 and 3.88 respectively. Standardized rates remain very low. Sex ratio among twin couples is also very low (0.49 male vs 0.51 female births). A multiple linear stepwise regression on the twinning rates shows MZ rates to be influenced by birth order and father's age, and the DZ rates by mother's age and birth order.
Twinning in Greece
Authors: Kataki A. , Kouvatsi A.
Published: July 2016

Mean MZ and DZ twinning rates in seven big Greek cities were 3.2 and 4.75 per 1,000 maternities, respectively, during the 1980-1985 period. The seasonal variations in twinning frequencies are not significant. The total twinning rate in Greece shows a decreasing trend from 1956 to 1985.
The Effect of Twins on Family Relationships
Authors: Sandbank Audrey C.
Published: July 2016

The results of the Bene Anthony Family Relations Test on 53 pairs of twins and 30 older siblings, as well as an analysis of personality inventories from their parents, are presented. It is shown that weight and birth order can affect not only personality and the way in which twins interact with each other, but can also affect family interaction. Particular attention has been given to the effect on and of the preceding sibling.
Grief in Multifetal Death
Authors: Sainsbury Mary Kay
Published: July 2016

The grief process is examined within the framework of multifetal pregnancy in a variety of demise situations. The case studies examined were obtained from approximately 120 lettere and interviews with families predominantly of higher order multiple births, who have experienced either partial or total loss in their pregnancy or afterwards. Objective and subjective factors were addressed. Results indicate the steps of the grief response are worked through in the same order as a singleton demise, but differ in intensity, duration, and frequency, depending on the individual circumstances, type of loss, gestational age, and the parents' backgrounds, expectations and beliefs. A unique feature discovered is that the entire grieving process, from shock through acceptance, appears to be completely experienced twice, with a large percentage of parents experiencing all of the stages three or more times. The general conclusion of the study is that the grieving pattern in multifetal death indeed follows a cycle and pattern of its own and requires special considerations.
The European Multiple Birth Study (EMBS)
Authors: Vlietinck R. , Papiernik E. , Derom C. , Grandjean H. , Thiery M. , Derom R.
Published: July 2016

The more that twin and other multiple pregnancies are investigated, the more it becomes mandatory that collaborative studies are set up in order to attain the criticai number of cases needed to achieve meaningful and reliable results. The European Multiple Birth Study (EMBS) aims to study two aspects of twin and multiple pregnancy: 1) management of pregnancy and labour, with emphasis on the prevention of preterm delivery; 2) accurate determination of zygosity, a prerequisite for the proper use of the twin method in a variety of fields, eg, congenital malformations, genetics, clinical investigations, etc. The rationale, the methods and the organisation of the study are described and discussed.
Management of Triplet Pregnancy
Authors: Pons J.C. , Mayenga J.M. , Plu G. , Forman R.G. , Papiernik E.
Published: July 2016

Based on the outcome of 21 triplet pregnancies from Antoine Béclère Hospital, early diagnosis in the major requirement for improving rates of fetal survival in multiple pregnancies. The outcome was better in mothers with spontaneous ovulation than in those with induced ovulations. Elective cesarean section in proposed.
Mode of Delivery in Multiple Birth of Higher Order
Authors: Feingold M. , Cetrulo C. , Peters M. , Chaudhury A. , Shmoys S. , Geifman O.
Published: July 2016

A retrospective review of triplets delivered at a Boston perinatal center from 1977 to 1986 was performed. Comparison was made between this group (study group) and previously published data on triplets in our institution (control group). Since 1977 there was a more liberal use of abdominal delivery. Cesarean sections (CS) of all triplets with malpresentation was our protocol. Of the 15 sets of triplet pregnancies in the study group, 11 were delivered by CS and 4 by vaginal delivery, vs only 1 CS in the control group wich consisted also of 15 triplets. The corrected mortality rate in the study group was lower than in the control group (2.6% vs 7.1%) but did not reach statistical significance. Apgar scores at 1 and 5 minutes were significantly higher in the study group (P < 0.002). Apgar scores for the third triplet were also higher in the study group (P < 0.05). In comparing the combined mortality and morbidity between the study group and the control group, no difference was found in the first triplet, but those of the second and third triplets were significantly lower in the study group. Of interest is the finding that the combined mortality and morbidity was not different statistically among the first, second, and third triplets in the study group, while in the control group an increase from the first to the third triplet was noted (21%, 31%, and 43%, respectively). A more liberal approach toward abdominal delivery of pregnancies of higher fetal number is advocated.
A New Method for Representing Mental Growth
Authors: Wilson Ronald S.
Published: July 2016

A new method is described for plotting the growth in mental development from birth to adolescence. Using data from a large sample of twins followed since birth, a dimension of mental growth was constructed by arraying all tests in order of difficulty, then computing the average gain from age to age. The gain was expressed in standard-deviation units, which reflected the upward shift in the score distribution from time X to time X + 1. When cumulated over ages, the scores generated a mental growth curve for the sample as a whole, as well as for each case individually. The curves displayed a very rapid gain in mental growth over the first 24 months of life, with the complexity of mental functions advancing by nearly 20 standard deviations from birth to two years. Thereafter the gain progressively tapered off until reaching a final increment of 0.5 SD gain between 15 years and adulthood. At this point, the terminal level of mental growth reached an average value of 31 SD units, with a spread of individual differences equal to ± 3 SD units. The scores at each age represented a combination of base level plus gain from the preceding age, and during infancy the gain scores were large in relation to base. At later ages, however, the gain scores were comparatively small, both in absolute terms and in relation to base. These characteristics help explain the typical low-order correlations obtained among mental test scores during infancy, vs the progressively larger correlations obtained at later ages.
Developmental Research of Twin's Temperament
Authors: Matheny Adam P.
Published: July 2016

In the Louisville Twin Study, pairs of 3- and 4-year-old twins were provided with standardized competitive or cooperative tasks in a laboratory setting. Some tasks required a pair of twins to share toys; other fostered a more competitive engagement between the twins. Behavioral ratings identified temperament and social components at both ages, and between the two ages, there were transformations in the links between the components. Parental ratings of the twins' temperament at the same ages were moderately correlated with the laboratory observations, but the pattern of the relations changed from one age to the next. The combined sets of measures were subjected to twin analyses for 43 pairs of twins. The results are discussed in terms of the similarity of MZ and DZ pairs for the dimensions of temperament and the transformations of temperament.
Longitudinal Research on Temperament in Twins
Authors: Torgersen Anne Mari
Published: July 2016

The changing influence of genetic factors of temperamental individuality has been studied longitudinally in a group of 44 same-sexed twin pairs at four different ages from infancy to puberty. Previous results showed that genetic factors seemed to play an important role in the development of temperamental characteristics when the twins were in infancy and at six years of age. The present report shows that when the within-pair differences in temperament are studied again at age 15 years, the similarity of identical pairs is even higher than at earlier ages. When shared and nonshared stress in the twin pairs was assessed at this age, some interactions were found between within-pair differences in temperament, stress and zygosity.
Multivariate Analysis of Genetic and Environmental Influences for Longitudinal Height and Weight Data
Authors: Fischbein S. , Pedersen N.L.
Published: July 2016

A multivariate analysis of genetic and environmental influences on longitudinal height and weight data from a Swedish twin sample is presented. For height in boys, genetic correlations of all ages with the first time point decrease during puberty and increase afterwards. A more linear pattern is evident for the girls. For weight in boys, genetic and environmental correlations are similar to the ones for height. Genetic correlations for girls are stable with age, while environmental correlations peak at 13.5 years and decrease drastically thereafter. The patterns for height and weight in boys suggest that a new set of genes may be turned on during puberty and turned off again afterwards. The pattern found for weight in girls indicates that a simple additive genetic model is not appropriate. It is necessary, however, to apply the model to actual data from several time points to recognize the inadequacy of the model.
Early Influences on the School Social Adjustment of Twins
Authors: Hay D.A. , O'Brien P.J.
Published: July 2016

The birth of twins is often accompanied by complications which may affect both twins equally (eg, prematurity) or which may establish differences between the twins (eg, one coming home from hospital first). Parents' ratings of behaviour may reflect and even perpetuate the influence of such variables and it is of interest to see if people less familiar with the twins' history can observe any long-term effects. In the La Trobe Twin Study teachers routinely complete the Bristol Social Adjustment Guide, an assessment of social maladjustment in children aged 5-16 years. Extreme prematurity and problems at delivery were generally associated with the Underreaction syndrome - the child who is unforthcoming, withdrawn and depressed. Withdrawal, depression and maladaptive behaviour to classroom peers were much more common among those twins discharged from hospital after the cotwin. A major mediating factor was that the parents admitted to greatly preferring the one to come home first. These raise questions both about the practice of bringing twins home separately (which occurred in 21% of the cases) and about intervening variables in studies of personality and temperament.
Prospects for Detecting Genotype × Environment Interactions in Twins with Breast Cancer
Authors: Martin N.G. , Eaves L.J. , Heath A.C.
Published: July 2016

We consider a study of MZ and DZ twin pairs ascertained because one or both twins have a disease. Genotypes at a major locus are known and putative environmental risk factors have been measured for all individuals. The power of the study to estimate the effect on liability of the measured and residual genetic and environmental effects (Gm, Gr, Em, Er) and all two-way interactions between them (except Gr × Er) is estimated by simulation. If liabilities can be indexed on a continuous scale (eg, blood pressure as an index of liability to hypertension), then a study of 600 MZ and 600 DZ pairs would have sufficient power to detect quite subtle interaction effects, even if ascertainment is greatly biased toward MZ twins. If liabilities cannot be measured and only affection status is known, then the power of the study would be much lower, although not impracticably so. There appears to be no advantage in augmenting the twins with a sample of control individuals who have been drawn at random from the population regardless of disease status, at least for the case we have considered in which the disease threshold on the liability scale is assumed to be known without error. The argument is developed in terms of the utility of the design for research into breast cancer.
Constrained Maximum Likelihood Analysis of Familial Resemblance of Twins and Their Parents
Authors: Boomsma D.I. , Molenaar P.C.M.
Published: July 2016

When the univariate twin design is extended by including parents of twins, it is possible to assess additive genetic effects in the presence of assortative mating and genotype-environment correlation, the effects of parental influence, as well as the extent of residual shared environmental influences. The analysis of data obtained in such an extended twin design can be carried out by means of constrained maximum likelihood confirmatory factor analysis. Specifically, the structural model underlying this design can be represented as a LISREL model with nonlinear constraints. This representation offers the possibility to consider extended multivariate twin designs involving common genetic and environmental factors. The proposed method will be illustrated with applications to simulated and real data.
Spectral Analysis of Twin Time Series Designs
Authors: Molenaar P.C.M. , Boomsma D.I.
Published: July 2016

The genetic analysis of physiological time series has to accommodate the presence of autocorrelation. This can be accomplished by means of orthogonal transformation of the series, thus enabling the use of standard genetic analysis techniques for the sequence of uncorrelated transforms. In view of the oscillatory character which typifies various physiological time series, it is customary to invoke spectral techniques for the analysis of these series. It can be shown that spectral analysis is an orthogonal transformation that asymptotically resembles principal component analysis. Consequently, standard genetic analysis methods for the uncorrelated spectral transforms may be used. This approach will be illustrated with simulated and real (heart rate) data for univariate twin time series. Furthermore, it will be indicated that the proposed analysis can be readily generalized to multivariate time series.
The Vietnam Era Twin (VET) Registry: Method of Construction
Authors: Eisen S. , True W. , Goldberg J. , Henderson W. , Robinette C.D.
Published: July 2016

A Vietnam Era (1964-1975) Twin Registry of American male-male veterans born between 1939 and 1955 has been developed to provide a study sample for research evaluating the impact of Vietnam service on the medical and psychosocial aspects of health. In preparation for developing the Registry, several alternative sources of twins and methods for identifying twins were investigated. A computerized database of veterans discharged from the military after 1967 was selected as the source because it contains about 50% of the total Vietnam era veteran population, is reasonably unbiased, and provides a feasible method for identifying twins. Twins were identified using an algorithm which involved matching entries on the database for same last name, different first name, same date of birth, and similar social security number. Twin status was confirmed by review of military records. The registry, now complete, is composed of 7,400 twin pairs. It will be an important resource for future research projects.
Do Breech Presentations in Twins and Singletons Run Different Risks?
Authors: Buekens P. , Lagasse R. , Puissant F. , Leroy F.
Published: July 2016

We have compared breech twins and breech single births in a population recorded between 1974 and 1978 in 10 Belgian maternity centers. In 190 twin pregnancies, 38 first and 65 second twins were delivered in breech presentation. These twins were compared to 853 singleton breeches, of which 95 delivered by cesarean section were excluded. Data were stratified according to birthweight. No significant difference between twins and singletons was found in terms of perinatal mortality rates. However, Apgar scores below 7 at 5 minutes were significantly less numerous among first twins than among singletons. Therefore, first twins in breech presentation might be at lower risk of fetal distress. This difference should be taken into account in the management of first twins presenting by the breech.
Fetal Alcohol Syndrome in Twin Pregnancy
Authors: Chasnoff Ira J.
Published: July 2016

In recent years, it has been realized that some infants of frankly alcoholic mothers escape the stigmata of fetal alcohol syndrome (FAS) and others have only a few of the characteristics. These infants are thought to display fetal alcohol effects (FAE). The controversy regarding the amount of alcohol a woman can safely drink during pregnancy and the effects of timing and individual physiology on producing FAS vs FAE in the infant are important questions which can perhaps be partially answered through examining twin pregnancies and offspring. Data are presented regarding the long-term growth and development of a set of dizygotic twins, one with FAS and one with FAE, delivered to a mother who drank moderate amounts of alcohol during pregnancy. The variation in the degree of abnormality found in dizygotic twins exposed to similar amounts of alcohol at the same time during gestation indicates that differences in fetal susceptibility to ethanol dysmorphogenesis are of prime importance to the expression of the fetal alcohol syndrome.
Umbelical Waveforms in Twin Pregnancy
Authors: Giles W.B. , Trudinger B.J. , Cook C.M.
Published: July 2016

Continuous wave Doppler ultrasound was used to study the twin fetus in 76 multiple pregnancies. The technique is not difficult and allowed the identification of the small for gestional age twin in both intrauterine growth failure and twin to twin transfusion syndrome.
Twin Studies in Craniofacial Genetics: A Review
Authors: Nakata Minoru
Published: July 2016

A review of the literature on twin studies in craniofacial genetics is presented. The following areas are particularly dealt with: tooth form and size, tooth formation and eruption, dental arch and occlusion, facial form and size, and cleft lip and palate.
Cotwin Closeness in Monozygotic and Dizygotic Twins: A Biasing Factor in IQ Heritability Analysis?
Authors: Tambs K. , Sundet J. M. , Berg K.
Published: July 2016

For 98 pairs of MZ twins, four measures indicating degree of cotwin closeness were correlated with absolute differences between IQ scores within pairs. In two different twin samples (40 MZ vs 40 DZ pairs and 169 MZ vs 174 DZ pairs, respectively), means and standard deviations in the closeness variables were obtained for MZ and DZ pairs. Whereas MZ cotwins were clearly closer than DZ cotwins, the relation between cotwin closeness and similarity in IQ seemed rather weak and ambiguous. “Years lived together in childhood home” were positively related to similarity in IQ (P < 0.01), whereas subjective feeling of closeness in contact tended to be negatively related to similarity in IQ.
Genetic and Environmental Factors in Head and Face Measurements of Belgian Twins
Authors: Susanne Charles , Defrise-Gussenhoven Elisabeth , Wanseele Piet Van , Tassin Arille
Published: July 2016

Seventeen head and face measurements of 205 twin pairs, aged 18 to 25 years, are analyzed. In both sexes a significant genetic variance component is found for head length, head breadth, and frontal breadth, for seven breadth measurements of the face, for physio-face height, and nose height. A significant genetic variance component is found for nasion-gnathion, nasion-stomion, and lips height in males and for the two ear measurements in females. We suggest that the sex difference for heritability may be due to random factors and to continued growth from 18 to 25 years in males.
The Northwestern University Twin Study XV: Rationales for a Standard of Care in Compromised Twin Pregnancies
Authors: Minogue J.P. , Tamura R.K. , Keith L.G.
Published: July 2016

Current antenatal technologies have improved the obstetrician's ability to assess fetal well-being as well as to diagnose fetal compromise. These technologies have given rise to very difficult ethical issues in the management of compromised twin pregnancies: for example, a choice must be made between putting a healthy twin at risk due to preterm delivery for the sake of a compromised cotwin or of allowing the compromised twin to die in order to buy time for the healthy twin. Though each case is unique, good medical practice requires a standard of care by which consistent patient management can be proposed. In the pluralistic environment of Northwestern Memorial Hospital, our staff has favored a standard of care based on patient autonomy. This approach demands: 1) a practitioner who offers a thorough explanation of the diagnosis and possible treatment approaches; 2) time for the patient and her partner to assimilate this information and test treatment options against their personal value system; 3) a third, but disinterested, party to facilitate patient understanding and value clarification; 4) a practitioner either willing to support the patient's decisions or refer her to another practitioner who will.
Estimated Fetal Weight in Twin Pregnancy: How Good Are We?
Authors: Campbell D.M. , Smith A.P. , Wilson A.W.
Published: July 2016

Ultrasonic assessment of fetal weight derived from multiple measurements of the fetus has become accepted in clinical practice as being useful in singleton pregnancies. Several different formulae for estimating fetal weight have been derived from differing measurements of the fetus, such as biparietal diameter, trunk circumference, and femur length. To date, there has been no attempt to evaluate such a technique in multiple pregnancy. This study aims to see whether the formulae derived for singleton pregnancy are applicable to twin pregnancies. Estimated fetal weight will be derived by mathematical modelling from ultrasonic measurements made within a week of delivery and the results compared with the actual birthweight to give an indication of how good such estimated fetal weights are. Factors to be considered in the analysis include whether there are differences between Twin I and Twin II, differences of presentation with twins and differences by gestation at delivery.
Simultaneous Genetic Analysis of Longitudinal Means and Covariance Structure Using the Simplex Model: Application to Repeatedly Measured Weight in a Sample of 164 Female Twins
Authors: Fischbein S. , Molenaar P.C.M. , Boomsma D.I.
Published: July 2016

The simultaneous analysis of means and covariance structures is applied to longitudinal twin data. Body weight was measured on six occasions in a sample of young female MZ and DZ twins. When average body weight at the first measurement occasion, as well as the increments in weight at later occasions, are specified in the genetic part of the model that also adequately explains the covariance structure, a good fit is obtained. In this application the increase in body weight at each occasion is weighted by the square root of the genetic variance innovation terms that represent the new genetic variance entering into the process.
Genetic Influences on Neonatal Temperament
Authors: Riese M.L.
Published: July 2016

The genetic contribution to temperament was assessed during the neonatal period in 172 newborn infants from 47 pairs of monozygotic (MZ) and 39 pairs of same-sex dizygotic (DZ) twins. Zygosity was not related to the neonatal temperament variables. Examination of the scores for twin concordance indicated significant within-pair concordance in temperament ratings, but MZ twins were not more like each other than DZ twins. The results suggested that neonatal temperament was influenced by environmental factors. Further analyses indicated that neonatal temperament was influenced by perinatal variables such as birth weight, 1- and 5-minute Apgar scores, and number of days spent in the hospital. It was concluded that there was no clear pattern of genetic influence on neonatal temperament, and that nonshared environmental factors were an important source of variance for temperament during this period.
Permissiveness-Restrictiveness for Twins and Controls in Two Educational Settings: The Swedish Compulsory School and the Israeli Kibbutz
Authors: Fischbein S. , Guttman R. , Nathan M. , Esrachi A.
Published: July 2016

In a previous longitudinal twin project a model was developed for studying heredity-environment interaction. One important environmental dimension in this model is permissiveness-restrictiveness. The purpose of the present study has therefore been to investigate perceived and imposed restrictiveness at the societal and classroom level and possible interactional effects on pupil behavior. Results are reported from grade 4 to grade 6 in Israeli kibbutzim and Swedish compulsory school. One major finding is that no systematic differences have been found between twins and controls in the two countries. In both Swedish schools and Israeli kibbutzim permissiveness-restrictiveness will vary depending upon perspective (perceived or imposed) and upon content (type of subject or rule-breaking activity). Preliminary within-pair comparisons for the Swedish twins are reported for different types of test results. In agreement with the model, logical abstract thinking as well as reading and mathematics achievement seem to be less influenced by hereditary factors in a restrictive educational setting than in a permissive one.