bluuebunny/crossref_metadata_2025 huggingface dataset:
Echocardiography, Angio-TC and Angiography in Assessing the Feasibility of Separation of Thoracopagus Twins
Authors: Gugliantini P. , Santoro G. , Formigari R. , Marino B.
Published: July 2016

Thoraco-abdominal fusion of twins is a rare malformation (1/50.000 live births) known as “Thoracopagus sternopagus tetrabrachius”. Most of the therapeutic problems encountered concern the degree of cardiac and hepatic fusion involved and this may be assessed by performing echocardiography, angio-TC and angiocardiography together with the conventional radiology techniques.

Case report. Two month-old ‘conjoined twins’ (Alphonsine Al, and Stephany St) with thoraco-abdominal fusion were admitted to our hospital. Gastrointestinal tract contrastography failed to show any comunication between the twins. Echocardiography showed cardiac fusion at atrial and ventricular level. Al showed a well-formed heart with a small atrial septal defect and mild aortic stenosis, while St showed a common atrium, fused with the left atrium of Al, connected by a common atrioventricular valve with a discordant single ventricle of left type (ventricular L-loop). No evidence of pulmonary trunk was found. Computed tomography and angio-TC confirmed cardiac and hepatic fusion showing a common arterial hepatic circulation. Cardiac catheterization and angiocardiography of Al confirmed a mild aortic stenosis and showed a severe aortic coarctation with the lower part of the body served by artero-arterial anastomoses of St, whose ventriculography showed pulmonary atresia and pulmonary hypovascularity. Arterial oxygenation of both circulations was provided by Al via atrial and ventricular fusion, while peripheral perfusion was mainly due to the systemic circulation of St. In conclusion, echocardiography, angio-TC, and angiography integrate the conventional radiographic techniques and are useful diagnostic tools to clarify the anatomy and/or physiology of thoracopagus twins, and to evaluate the feasibility of their surgical separation.
Limb Body Wall Complex and Sirenomelia in Twins
Authors: Russo R. , Vecchione R.
Published: July 2016

The coexistence of Limb body wall complex (LBWC) and Sirenomelia sequence (SS) is present in only two studies in the literature on the topic. Tang et al (1991) and Martinez-Frias et al (1992) examined single fetuses and pointed out that the association of these two phenomena is extremely rare. The present study further contributes to the investigation and description of this particular association in a pair of twins. Both twins presented abdominal defects, urogenital anomalies and persistence of the primitive cloaca, but did not show craniofacial (CF) defects or amniotic band related defects. One twin had one leg only. In a previous study on LBWC we identified two morphologically and pathogenetically different phenotypes which, among other characteristics, are identifiable by the presence or absence of CF defects. (Russo et al. 1993; Russo et al. in press). Our twin pair belongs to the LBWC group without CF defects. This group, like SS cases, is usually characterized by the presence of lower limb anomalies. Aside from this, they also share a similar pattern of anomalies involving the urogenital tract and the cloaca. Analysis of the anomalies present in the twin pair leads us to suggest that the Sirenomelia pattern might be at the extreme end in a spectrum of lower limb defects within the LBWC group that does not present CF defects. In brief, we suggest that the coexistence of this LBWC type and SS is not related to the occurrence of two different defects but is the consequence of a common maldevelopmental process occurring during blastogenesis.
The Incidence of Superfecundation and of Double Paternity in the General Population
Authors: James W. H.
Published: July 2016

It is estimated that at least one dizygotic (DZ) twin maternity in twelve is preceded by superfecundation (the fertilization of two ova by sperm from different coitions). Presumably this parameter varies from population to population eg. with coital rates and rates of double ovulation. Sometimes superfecundation occurs by two different men. The frequency with which this occurs must depend on rates of infidelity (promiscuity). It is suggested that among DZ twins born to married white women in the U.S., about one pair in 400 is bipaternal. The incidence may be substantially higher in small selected groups of dizygotic twin maternities, eg. those of women engaged in prostitution.
Latent Menstrual Cycle in Pre-Menarcheal Monozygotic Twins
Authors: Nakamura I. , Harada C. , Miura T.
Published: July 2016

The distribution of menarcheal interval-length between cotwins in 67 pairs of female identical twins in Tokyo was found to cluster at fairly constant intervals. When delayed in one twin, the menarche occurred in the second twin at intervals of approximately 28 days after that of the earlier twin. This finding suggests the existence of a latent lunar or menstrual cycle in pre-menarcheal girls, evidence for which was detected by recording the menarcheal intervals between MZ cotwins in days.
Ethnicity and Sex Ratio in Twin Births
Authors: Picard R. , Fraser D. , Picard E.
Published: July 2016

The patterns of sex ratio in Israeli twins by maternal age and parity are described in two ethnic subpopulation. Jews and Bedouins differ one from the other in genetic, environmental, lifestyle, and reproductive factors. In the Jewish subpopulation, the proportion of males was significantly lower in twin than in singleton births; parity increased the odds of male twin births while maternal age had the inverse effect. In the Bedouin subpopulation, the sex ratio did not differ significantly from that of singletons, and no consistent patterns were found by maternal age and parity. The data suggest that several factors may influence the sex ratio in twin births. In Jewish twin births, the findings are consistent with the literature and can be largely explained in terms of high level of maternal gonadotropins. In the Bedouin subpopulation, paternal influence which could be related to lifestyle may be present, and as yet undefined genetic factors may also be involved. It would be of great interest, therefore, to continue monitoring of the effects of changes in lifestyle on the Bedouin population in order to tease out the relative importance of the varying factors on the sex ratio of twin births.
Acid-Base Differences in Preterm and Term Twin Pregnancy
Authors: Ordorica S.A. , Hoskins I.A. , Young B.K.
Published: July 2016

A prospective study was undertaken which examined 179 sets of twins, 68 premature (less than 36 weeks of gestation) and 111 term. The purpose of this study was to assess differences in the acid-base status between twins related to gestational age, birth order and the time interval between twin births. Although the twin blood-gas data is within the range considered normal, statistically significant differences favoring the first-born were noted for both preterm and term twins. These differences do not depend on gestational age, route of delivery or presentation, and become evident when the interval between twin births exceeds one minute. We postulate that after delivery of the first twin, the reduced uterine size causes a decrease in the intervillous blood flow and consequently a reduction in the respiratory exchange between the second fetus, still in utero, and its placenta.
Maternal Plasma Concentrations of Insulin-Like Growth Factor-I (IGF-I) and Human Placental Lactogen (hPL) in Twin Pregnancies
Authors: Kazer R.R. , Cheng E.R. , Unterman T.G. , Glick R.P.
Published: July 2016

Maternal plasma IGF-I and hPL concentrations were examined in 10 singleton pregnancies and in 11 twin gestations near term. hPL concentrations were higher in the twin pregnancies (14.4 ± 2.4 μg/1 vs 6.9 ± 0.9 μg/1, P < 0.02). In contrast, plasma IGF-I concentrations were similar in the singleton and twin pregnancies (533 ± 45 μg/1 vs 572 ± 60 μg/1, respectively). IGF-I concentrations failed to correlate with hPL concentrations in either group separately or when all subjects were considered together. These data do not support the hypothesis that maternal IGF-I secretion is an hPL-dependent process.
Twin Pregnancy Complicated by Intrauterine Demise of One Fetus
Authors: Loverro G. , Ranieri D.M. , Greco P. , Selvaggi L.
Published: July 2016

Two cases of antepartum demise of one fetus in a twin pregnancy are reported. Obstetrical management and fetal outcome are discussed with particular respect to changes in maternal coagulation parameters.
Variable Number of Tandem Repeats in Zygosity Diagnosis in Twins
Authors: Porrini S. Costanzi , Sciarra A. , Sulli N. , Piane M. , Gualtieri R. , Porto G. Del
Published: July 2016

The use of DNA restriction fragment length polymorphisms (RFLP) to analyze variable number of tandem repeat (VNTR) sequences dispersed in the human genome, has become a powerful tool for the study of population genetics due to the very substantial polymorphism involved. Because the markers usually employed for twin zygosity determination (such as sex combination, placentation, HLA typing, blood group antigens, etc) may not be uniformly informative, we propose the use of synthetic olygonucleotides, representing VNTR “core” sequences, for the determination of zygosity in twins.
The Northwestern University Twin Study. VII: The Mode of Delivery in Twin Pregnancy - North American Considerations
Authors: Depp R. , Keith L.G. , Sciarra J.J.
Published: July 2016

No consensus exists for the optimal mode of delivery for twin fetuses. Opinions vary by type of institution (university medical center vs community hospital), country or continent (North America vs Western Europe) and personal preference of individual physicians. This article lists clinical considerations in arriving at the decision and presents them in the form of a decision tree.
The Northwestern University Twin Study. VIII: On the Causes and Care of Multiple Pregnancy
Authors: Keith L.G. , Method M.W. , Depp O.R. , Keith D.M.
Published: July 2016

Recent clinical literature on the causes of twin pregnancy and specific areas of antenatal care are reviewed. Controversial aspects of clinical management are discussed.
Fetal Growth in Twin Pregnancies
Authors: Neilson J.P.
Published: July 2016

In 65 consecutive twin pregnancies, 722 measurement of fetal abdominal circumference have been obtained with ultrasound. Zygosity was established after delivery in 85% of the pregnancies. There was no difference in mean abdominal circumference measurements between monozygotic and dizygotic pregnancies. In both groups, the pattern of growth was linear throughout pregnancy in contrast to that predicted by birth-weight for gestational age charts. It is suggested that increasing trunk flexion, in later twin pregnancy, may distort accurate abdominal circumference measurement.
The Northwestern University Triplet Study. I: Overview of the International Literature
Authors: Keith L.G. , Ameli S. , Keith D.M.
Published: July 2016

The international literature on triplet births is surveyed. No definitive work on triplet gestations exists. The relatively few articles on this subject are divided into three categories: 1) national data; 2) local, regional or hospital series; 3) case reports. Clinical concerns, such as prematurity, low birth weight, bed rest, and tocolysis, are discussed with specific reference to literature citations.
Early Developmental Progress of Preterm Twins Discordant for Birthweight and Risk
Authors: Stauffer A. , Burns W.J. , Burns K.A. , Melamed J. , Herman C.E.
Published: July 2016

Studies of developmental progress in high-risk twins have disparate findings. In this study, we report the outcome of 45 twin pairs born between 26 and 37 weeks gestation, and whose birthweights ranged from 840 to 2000 g. No significant differences were found for weight, risk and birth order. However, earlier preterm infants were found to have significantly lower mental scores on the Bayley Scales of Infant Development at 24 months, and lower IQ scores on the Stanford Binet Intelligence Scale at 36 months. These findings imply that gestational age is a powerful variable in determining developmental outcome.
Speech and Language Development in Preschool Twins
Authors: Hay D.A. , Prior M. , Collett S. , Williams M.
Published: July 2016

While language, articulation and reading problems have been well documented in young twins, it is not clear how extensive such problems can be or how early in childhood they become evident. At the age of 30 months, twin boys in the La Trobe Twin Study were 8 months behind matched singletons and twin girls on expressive language and 6 months behind on verbal comprehension. They were also 5 months behind on symbolic play and this delay was closely related to language. “Secret” language characterised most of the twin boys but not the girls and the relation of this to articulation delays is discussed. To examine if exposure to other children helps the twin boys, 38-53 month old twins and singletons were matched on the Columbia Mental Maturity Scale at the time of starting preschool. The twin boys had more articulation problems and all twins scored much lower on a Sociability questionnaire completed by the teacher. After 8 months at preschool, all children had advanced in Sociability, but the twins remained just as far behind with poor Sociability relating to poor articulation. The role of intervention programs is discussed.
The Expectation and Parentage of Twins A Study on the Language Development of Twin Infants
Authors: Alin-Åkerman Britta
Published: July 2016

This is a follow-up study aiming to describe personality development of twins and possible differences at different ages. The investigation was conducted at the Mother Clinic in the Karolinska Hospital in Stockholm. This report describes the language development of 35 twin pairs at 9 months of age. The development values show that no greater differences exist for girls between twins and singletons. The language result is however lower. The boys, on the other hand, have considerably lower results both on total development scale and on the language scale.
Dominance and Submissiveness Between Twins. I. Perinatal and Developmental Aspects
Authors: Moilanen Irma
Published: July 2016

Factors predicting dominance and submissiveness between twins were analyzed in a longitudinal study of 234 twin pairs. Boys were found to be physically dominating, while the girls more often were psychically dominating and in the role of the spokesman. Low birth weight, to be second born, or low Apgar score tended to predict submissiveness, but not significantly. The same was true concerning perinatal asphyxia and hypoglycemia, which also showed some potential cumulative effect when occurring simultaneously. Those having developed faster or with higher intelligence were more often the leaders of the twin pair. Probably good neonatal care in modern hospitals tends to prevent perinatal damage, and therefore the previous findings of second born or small birth weight twins being most submissive was not fully established.
Multimethod Assessment of Temperament in Twins: Birth to Six Months
Authors: Riese M.L. , Wilson R.S. , Matheny A.P.
Published: July 2016

The predictive relationship between neonatal behavior and temperament at 6 months was assessed in 62 pairs of twins. The neonatal assessment evaluated irritability, resistance to soothing, reactivity, and activity level across various activities. Temperament at 6 months was appraised by a laboratory assessment, ratings on the Infant Behavior Record, and a questionnaire completed by the mother. Examination for temperament consistency from the neonatal period to 6 months indicated that (a) neonates rated by an examiner as irritable and difficult to soothe were reported by the mother to be more negative, irritable, and slower to adapt at 6 months; (b) neonates rated as more irritable and active were more attentive and responsive during mental testing at 6 months; (c) there was no relationship between the neonatal measures and the laboratory ratings, possibly reflecting methodological problems influenced by maturation and vegetative processes at 6 months. Analyses for patterns of concordance within the various data sets for MZ and DZ twins indicated that there was no pattern of differential concordance favoring MZ twins for the temperament measures at birth or at 6 months. It was concluded that a modest predictive relationship between temperament variables had been demonstrated from birth to 6 months, but no specific genetic effects were detected at these early ages.
Resting Metabolic Rate in Monozygotic and Dizygotic Twins
Authors: Fontaine E. , Savard R. , Tremblay A. , Després J.P. , Poehlman E. , Bouchard C.
Published: July 2016

In order to study the influence of heredity on resting metabolic rate (RMR), 20 monozygotic and 19 dizygotic male twin pairs aged 20.6 (SD 2.9) and 21.4 (SD 3.1) years, gave their consent to participate in the experiment. Fat free weight (FFW) was estimated from underwater weighing. RMR was measured by indirect calorimetry using an open circuit system. RMR was expressed as kJ · min−1, kJ/m2· h−1, kJ/kg · h−1and kJ/kgFFW · h−1. Significant intraclass coefficients were observed in MZ twins for the different expressions of RMR. The values ranged from r = 0.45 (P < 0.05) to r = 0.81 (P < 0.01). However, DZ twins demonstrated lower intraclass coefficients for RMR, with a range from r = 0.21 to r = 0.44. Significant (P < 0.05) DZ resemblance was revealed only when RMR was expressed as kJ · min−1and kJ/kg · h−1. Results of the present study suggest that variations in RMR may have a genetic component. Implications for human energy balance and body fat are discussed.
Human Placental Lactogen and dU-Estrogen Levels in Normal Twin Pregnancies
Authors: Kappel B. , Hansen K. , Moller J. , Faaborg-Andersen J.
Published: July 2016

Reference intervals for human placental lactogen (hPL) and dU-estrogens (dU-E) in uncomplicated twin pregnancies are found to be higher than singleton pregnancies and considerably wider. Significantly more monozygotic than dizygotic pregnancies, and significantly more monoplacental than diplacental pregnancies showed hPL values below the median on the normal range curve. The same was not found for dU-E. Significantly more growth-retarded fetuses were found in monoplacental than diplacental pregnancies. The benefit of measuring the two parameters in order to identify the intrauterine growth retarded fetuses were evaluated in terms of sensitivity and specificity. Both parameters were found less suitable for the purpose.
Triplet Gestation: Maternal and Neonatal Implications
Authors: Syrop C.H. , Varner M.W.
Published: July 2016

Triplet pregnancy of over 20 weeks gestation occurred 20 times during 75,506 deliveries at a referral hospital. Commonly occurring maternal complications included premature delivery (75%), antepartum anemia (35%), postpartum hemorrhage (35%), preeclampsia (20%), and premature spontaneous rupture of the membranes (20%). Malpresentation was common. Neonatal complications were also common and included respiratory distress syndrome (45%), presumptive sepsis (36.6%), hyperbilirubinemia (33%), and neonatal death (21.6%). These high complication rates emphasize the importance of early identification and referral center care for these vulnerable pregnancies.
Twins with Acardia and Anencephaly
Authors: Pavone L. , Laurence K.M. , Mattina T. , Nuciforo G. , Mollica F.
Published: July 2016

The authors describe a pair of twins, one of whom showed acardia while the other had severe neural tube defect including anencephaly. This is the first observation of a fetal malformation (anencephaly) in the cotwin of an acardius and confirms the fact that even the cotwin of an acardiac fetus may be at risk of severe congenital malformations.
Language Disabilities in Three Twin Pairs and Their Relatives
Authors: Borges-Osório Maria R.L. , Salzano Francisco M.
Published: July 2016

Three pairs of monozygotic twins were ascertained during a general survey of language disabilities conducted among schoolchildren of Porto Alegre, Brazil. Two of them were concordant for dysgraphia, dysorthographia, dyslexia, and speech defects, while the other was concordant for dysorthographia and dyslexia, but discordant for dysgraphia. Two of the mothers and two sibs also presented language problems, but of a type that was not completely similar to those of the twins. Concomitant neurological and psychological studies, as well as the family histories, helped to understand the similarities and dissimilarities observed.
A Study of the Influence of Ovulation Stimulants and Oral Contraception on Twin Births in England
Authors: Webster F. , Elwood J.M.
Published: July 2016

A study of 111 mothers of twins in Nottinghamshire, England, in 1981-82 showed that at least 12 had used ovulation stimulants, compared to 2 of 102 mothers of singletons. Thus, the use of ovulation stimulants increased the twinning rate of this population by about 10 percent; this may explain the recently noted levelling off in the secular decline in twinning rates. In contrast to a recent study in France, no association between twinning and prior use of oral contraceptives was seen.
Possible Linkage Relationship Between Genetic Markers and Blood Magnesium and Zinc A Twin Study
Authors: Darlu P. , Defrise-Gussenhoven E. , Michotte Y. , Susanne C. , Henrotte J.G.
Published: July 2016

In a sample of 63 like-sex dizygotic twins, red blood ceE and plasma magnesium and red blood cell zinc concentrations were analyzed for linkage to each of 23 genetic systems by estimating correlation between proportion of genes identical by descent and biological resemblance for the trait. The results suggest possible linkage of red blood cell magnesium with the HLA locus and of red blood cell zinc with the GLO1 locus. However, studies applying more powerful tests are needed to confirm such conclusions.
Quantitative Analysis of C-bands in Chromosomes 1, 9, 16, and Y of Twins
Authors: Pedrosa Marise P. , Salzano F.M. , Mattevi Margarete S. , Viégas Judith
Published: July 2016

Thirty-two pairs of Caucasoid twins, 16 monozygotic (MZ) and 16 dizygotic (DZ) of the same sex, were studied by densitometry in relation to the C-bands of chromosomes 1, 9, 16, and Y. Confirming earlier results, concordance was not absolute among MZ. Estimates of the degree of genetic determination for these traits varied from 0.73 to 0.89 for the autosomes and from 0.86 to 0.95 for the Y. There are now stronger indications that a fraction of the intergeneration variability found in these structures may be real, probably due to mitotic and/or meiotic unequal crossing-over.
A Mathematical Model for Recurrent Twinning
Authors: Fellman J.O. , Eriksson A.W.
Published: July 2016

In an attempt to improve our understanding of the factors that affect human twinning, we further developed the models given by Hellin (1895) and Peller (1946). The connection between these models and our own model (“Fellman's law”) were studied. These attempts have resulted in a more general model, which was then applied to data from Åland Islands (1750-1939), Nîmes (1790-1875), Stuttgart (about 1790-1900) and Utah (1850-1900). The product of the mean sibship size and the total twinning rate can be considered as a crude estimate of the expected number of sets of twins in a sibship. The same can be said about the twinning parameter in our model. These estimates are in good agreement. If we consider twinning data only, we obtain the geometric distribution, and log (Nk), where Nk is the number of mothers with k twin maternities, is a linear function of the number of recurrences. Graphically, this property can easily be checked. For sibships containing three or more sets of twins, all four populations show higher values than expected, particularly the populations from Stuttgart and Utah, which data also show poor agreement according to a χ2-test. A more exact model would demand more detailed demographic information, such as distribution of sibship sizes, age-specific twinning rates and temporal variations in twinning.

The osberved number of mothers in Åland with several recurrences of multiple maternities shows a considerable excess over the expected number as predicted by Peller's rule. The parameters in our model can be estimated by the maximum likelihood method and the obtained model fits the data better then Peller's model.
Maternal Age and Parity as Predictors of Human Twinning
Authors: Bønnelykke B.
Published: July 2016

A case-control study was conducted to evaluate the association between maternal age and parity and dizygotic (DZ) and monozygotic (MZ) twinning, respectively. Mothers of all twins born alive in Denmark in 1984 or 1985 were included into the study as cases, and a random sample of mothers of singletons were controls. Data on maternal age at delivery and number of previous births were collected from the Danish Medical Birth Register. By means of logistic regression analysis, a significant and positive association was found betwen maternal age and DZ twinning, and a significant and negative association between parity and MZ twinning. No association was found for parity and DZ twinning, nor for maternal age and MZ twinning. The study suggests that human MZ twinning has predictors too, as has DZ twinning. The finding has implications for zygosity classification in future twin research.
The Effects of Maternal Age, Parity, and Sex of the Twins on Twin Perinatal Mortality. A Population Based Study
Authors: Rydhström H.
Published: July 2016

The aim of this study on all twin births in Sweden between 1973 and 1985 was to evaluate the effect of maternal age, parity, and sex on twin perinatal mortality (PNM), by using national data held at the Medical Birth Registry, National Board of Health and Welfare, Stockholm. Zygosity in this study was estimated by the Hardy-Weinberg formula. In all, 22,374 twins were born; 972 (4.3%) of these died perinatally. The relative risk for perinatal death (after standardization for maternal age, parity, and like sex) decreased significantly during the study period, and reached its lowest value (0.3) in 1983. Maternal age was not associated with PNM, while women having their first delivery had a significantly higher PNM than the rest of the parturients. The MZ twinning rate increased fom 0.36% during 1973-76, to 0.40% during 1977-81 and 0.44% during 1982-85 (trend analysis: χ2 = 40.1, p < 0.001). After stratification for year of delivery and birthweight, like-sexed twins had a significantly higher PNM than unlike-sexed twins (odds ratio, OR = 1.25, 95% confidence interval, CI = 1.02-1.54). Males had a significantly higher PNM than females in like-sexed pairs (OR = 1.39, 95% CI = 1.16-1.66), and in unlike-sexed pairs (OR = 1.46, 95% CI = 1.01-2.10). MZ twins had a significantly higher estimated PNM than DZ ones (OR = 1.31, 95% CI = 1.02-1.67).
The Influence of Birth Injuries in First-Born and Second-Born Twins
Authors: Asaka A. , Ooki S. , Yamada K.
Published: July 2016

This study showed that biological handicap with many complications at birth was much more recognized in the second-born than in the first-born twins. One of the most prominent intrapair differences was, for example, the weight at birth. However, intrapair differences, which were observed also in other physical measurements, diminished gradually with age. Moreover, as for intellectual ability, which was represented by the scores of the entrance examination test or standard achievement test, no remarkable influences due to handicap of the second-born were identified. Thus, it was concluded that the biological handicap seen in the second-born twin at birth did not give any significant effect on later development.
Growth Patterns in Preterm and Term Twin Deliveries
Authors: Smith A.P.M. , Campbell D.M. , Lemon J.
Published: July 2016

Preterm deliveries in singleton pregnancies have been shown to be associated with decreased rate of growth in utero. A total of 113 sets of twins were scanned serially at fortnightly intervals to establish fetal growth. There was no significant difference in the growth pattern in twins delivered before 37 weeks compared to those delivered after this time.
Genetic and Environmental Influences on Special Mental Abilities in a Sample of Twins Reared Apart
Authors: Bouchard T.J. , Segal N.L. , Lykken D.T.
Published: July 2016

The Minnesota Study of Twins Reared Apart has conducted comprehensive medical and psychological assessments of monozygotic (N = 49) and dizygotic (N = 25) twin pairs, separated early in life (average age of separation = 0.3 and 1.1 years, respectively) and reared apart during the formative years (average age of reunion = 30.3 and 37.2 years, respectively). The twins are administered two special mental ability batteries. The Hawaii Battery (H-B), supplemented by several Educational Testing Service tests, is administered toward the beginning of the assessment week. The Comprehensive Ability Battery (CAB) is administered toward the end of the assessment week. All data are age- and sex-corrected. The average MZA and DZA intraclass correlations for the 15 H-B subtests were 0.45 and 0.34, respectively, and the average MZA and DZA intraclass correlations for the 13 subtests of the CAB were 0.48 and 0.35, respectively. Biometric model-fitting of these data indicate an average heritability of about 0.50. Data for groups of subtests in the Verbal, Spatial, Perceptual Speed and Accuracy and Memory domains were compared to a meta-analysis of the special mental ability findings in the ordinary twin literature. The Spatial domain appears to yield the highest and the Memory domain the lowest heritabilities.
What Is It Like to Be a Parent of Twins?
Authors: Fischbein S. , Hallencreutz I. , Wiklund I.
Published: July 2016

A questionnaire was given to parents of twins concerning their perceptions of dependency and similarity in their twin children. Also, the parents were asked if they tried to influence their children to become more dissimilar. 70 samesex twin pairs (35 MZ and 35 DZ) were included in the study and a questionnaire was sent both to the mother and the father of the twins. The twins were approximately 12 years old and attended grade 4, 5 or 6 in the Swedish compulsory school. Results indicated that parents consider MZ twins to be dependent upon each other and to spend more time together. This was especially evident for girls. If the twins had a free choice they would also tend to choose similarly. This trend was also more pronounced for the MZ girls. Irrespective of zygosity, most parents reported that they did not try to influence their children. In the case of MZ twins this will probably make them become more similar over time. Differences between maternal and paternal answers tended to be nonsignificant.
Risk Factor Variability and Coronary Heart Disease
Authors: Berg K.
Published: July 2016

Present attempts to identify genes contributing to coronary heart disease (CHD) risk focus on “candidate genes”. With respect to CHD this could be any gene whose protein product is directly or indirectly involved in atherogenesis, thrombogenesis or thrombolysis/fibrinolysis. Genes that exhibit associations with absolute risk factor levels may be referred to as “level genes” to distinguish them from “variability genes”, which are genes involved in establishing the framework within which environmental influences may cause risk factor variation. In a series of persons recruited from the Norwegian Twin Panel, confirmatory evidence for level gene effect with respect to apolipoprotein B (apoB) concentration was found with an XbaI polymorphism in DNA at the apoB locus corresponding to residue 2,488 in the mature protein. Evidence for variability gene effect with respect to apoB as well as body mass index emerged with DNA variants in the 3′ part of the apoB gene. Level gene effect with respect to apolipoprotein A-I (apoA-I) and high density lipoprotein (HDL) cholesterol as well as apparent variability gene effect with respect to total and LDL cholesterol were detected with a DNA polymorphism at the cholesteryl ester transfer protein (CETP) locus. The first example of interaction between normal genes in determining risk factor level was uncovered in analysis of the apolipoprotein E (apoE) polymorphism and a restriction fragment length polymorphism (RFLP) at the low density lipoprotein receptor (LDLR) locus. An LDLR gene identified by presence of a PvuII restriction site eliminated completely the well known effect of the apoE4 allele on cholesterol level. Finally, in families where high Lp(a) lipoprotein level (a well established risk factor for CHD) segregated as a Mendelian trait, very close linkage with an RFLP at the plasminogen locus was established and DNA variation at the LPA locus reflecting varying numbers of a structure homologous to the “kringle IV” region of plasminogen was uncovered.
Cigarette Smoking As a Cause of Lung Cancer and Coronary Heart Disease. A Study of Smoking-Discordant Twin Pairs
Authors: Kaprio J. , Koskenvuo M.
Published: July 2016

Despite increasing scientific evidence for a causal role of tobacco smoking in lung cancer and coronary heart disease, an alternative hypothesis was put forward several decades ago. The constitutional hypothesis has stated that there are genetic or other common factors, which predispose both to smoking and disease. A critical test of this hypothesis was considered the pattern of occurrence of disease in monozygotic (MZ) twin pairs in which one is a smoker and the other never has been a smoker. Initial twin studies found only small differences in the mortality of smoking and nonsmoking twins of discordant pairs. In the Finnish Twin Cohort, a population-based panel of adult like-sexed twin pairs, a questionnaire study carried out in 1975 permitted identification of 2488 twin pairs discordant for cigarette smoking. Analyses of total mortality and mortality due to coronary heart disease and lung cancer indicate that the smoking members of discordant MZ pairs are at higher risk than their nonsmoking cotwins; increased mortality of smoking cotwins was also found on 21-year follow-up of smoking-discordant pairs in Sweden. Incidence data and noninvasive studies of atherosclerosis in the Finnish sample provide confirmatory evidence for the causal role of smoking in the etiology of coronary heart disease and lung cancer.
Chronological Changes in Genetic Variance and Heritability of Systolic and Diastolic Blood Pressure Among Chinese Twin Neonates
Authors: Yu M.-W. , Chen C.-J. , 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 chronological changes in genetic variance and heritability of arterial systolic and diastolic blood pressure (SBP and DBP) of Chinese infants in Taiwan, a total of 339 same-sexed twin neonates born in four major general teaching hospitals in Taipei City were studied. Based on placentation and 12 red blood cell antigens, 274 monozygotic (MZ) and 65 dizygotic (DZ) twin pairs were identified and followed up to the age of one year. Both SBP and DBP were measured by Doppler blood pressure monitor. Within-pair mean squares of SBP and DBP were consistently smaller in MZ than DZ twins at ages one month and over. The findings remained unchanged after the adjustment for the effects of age, sex, gestational age, placentation and physical state during blood pressure measurement. Falconer's heritability indices for adjusted SBP and DBP at ages two months and over ranged from 0.29 to 0.55 and from 0.27 to 0.45, respectively. The study indicates an important genetic influence on blood pressure during infancy.
Causes of Variation in Drinking Habits in a Large Twin Sample
Authors: Jardine R. , Martin N.G.
Published: July 2016

A genetic analysis of alcohol consumption in 3810 pairs of adult twins is reported. When no correction was made for age, individual environmental variance, including non-repeatable errors of reporting, accounted for approximately 44% of variation in both sexes. In females, there was no evidence of shared environmental effects and 56% of the variance was genetic in origin. In males, only 36% of the variance was genetic and common environmental effects accounted for the remaining 20% of individual differences.

For females, the results for younger (30 years and under) and older (over 30) twins were similar. For males, however, the effect of age was striking. In younger male twins over 60% of the variance was genetic in origin, with the remaining variance due to environmental influences unique to the indiviudal. In older twins genetic differences do not appear to be important, with approximately 50% of the total variance due to individual environmental differences and the remaining 50% due to the effect of the common family environment. Our results suggest that both age and sex need to be considered when analysing the causes of variation in alcohol consumption.
Preliminary Findings from a Study of the Effects of a Challenge Dose of Alcohol in Male Twins
Authors: Cobb M.J. , Blizard R.A. , Fulker D.W. , Murray R.M.
Published: July 2016

Twelve pairs of MZ and 7 of DZ normal adult male twins were given a challenge dose of 0.8 mg ethanol per kg body weight diluted to a 30% v/v solution. Measures of blood alcohol, mood, craving for alcohol, body sway, heart rate and four psychomotor tasks were taken before, during and after intoxication. Genetic factors were found to be involved in the response of heart rate, body sway and two of the psychomotor tasks, but not in changes in blood alcohol, alertness or craving for alcohol. Drinking habits did not exert a strong influence upon acute responses to alcohol, but were significantly related to craving for alcohol whilst intoxicated.
Heredity and Infectious Diseases: A Twin Study
Authors: Gedda L. , Rajani G. , Brenci G. , Lun M.T. , Talone C. , Oddi G.
Published: July 2016

A concordance study of 6 infectious diseases of childhood has been carried out in a sample of 656 twin pairs classified by sex and zygosity. A new approach is proposed to estimate the respective influence of heredity and of common environment. The estimates thus obtained range from 86% hereditary component in the case of measles to 100% environmental component in the case of scarlet fever.
Discordance for Skeletal and Cardiac Defect in Monozygotic Twins
Authors: Stoll C. , Roth M.P. , Dott B. , Bigel P.
Published: July 2016

A case of monozygotic male twins discordant for skeletal and cardiac defect is reported. One twin had the hemifacial microsomia type of the oculo-auriculo-vertebral dysplasia. The cotwin had no asymmetry of the face and normal ears, but preaxial polydactyly and ventricular and auricular septal defects. The cotwins were concordant for craniostenosis with a ridge metopic suture. Karyotypes were normal.
Zygosity Testing: Laboratory and the Investigator's Judgment
Authors: Segal Nancy L.
Published: July 2016

The immediate global impressions of zygosity (based upon physical similarity) were recorded by the investigator at initial meetings with 105 pairs of twins. The accuracy of these ratings, as well as classifications provided by two objective procedures (physical resemblance questionnaire; dermatoglyphic analyses) and two subjective procedures (parental impressions; physician's impressions), were evaluated by comparison with results from bloodtyping for 53 pairs. The judgments of the investigator furnished the most accurate indication of zygosity (94-96% accuracy). Laboratory tests were repeated for five pairs when the results proved incompatible with the investigator's ratings. In all five cases, the investigator's judgments were confirmed, indicating that a laboratory error had occurred. It appears that the opinion of a skilled observer of twins can provide a convenient and highly effective alternative to bloodtyping.
Race, Zygosity, and Mortality Among Twins: Interaction of Myth and Method
Authors: Boklage C.E.
Published: July 2016

For epidemiological purposes, it is customary to assume that same-sex (SS) dizygotic (DZ) twin pairs are approximately equal in number to unlike-sex (OS)-DZs, the remainder of the SS pairs being monozygotic (MZ). It is also customary to consider OS-DZs to be epidemiologically representative of all DZs, which can only mean that difference in frequency of any trait between OS and SS twins is due to the MZ fraction of the SS twins. Since this is assumed as a premise, there is little value in its usual appearance as the result. The basic tenet of twin biology, that most twin excess anomalies are due to MZs, is a myth self-perpetuated by a methodological tautology, and is false, at least for mortality. In a consecutively ascertained and prospectively studied sample of 616 twin pairs, over 80% diagnosed for zygosity, it can be shown that the standard assumption mentioned above have given impossible answers. The most probable possible answer is that mortality does not differ greatly with zygosity overall, but that SSDZ mortality is much higher than that of OS twins, and probably even higher than that of MZs. Race differences in the probable answers further suggest that standard assumptions of the Weinberg method may have consistently provided false explanations for race differences in the OS fraction of twin pairs.
Zygosity and Placental Structure in Monochorionic Twins
Authors: Mortimer G.
Published: July 2016

To test the assumption that monochorionic twins are monozygotic, cord bloods from 12 sets of monochorionic twins were tested for a total of 16 red cell antigens. Discrepancies were noted among the minor blood groups in 3 of the 12 sets. The result of this pilot study strengthens the contention of others who have previously questioned the general acceptance that monochorionicity and monozygosity are synonymous.
Genetic Variation and Plasma Creatine Kinase Activity
Authors: Whitfield J.B. , Martin N.G.
Published: July 2016

The distribution of plasma creatine kinase (CK; E.C.2.7.3.2) is known to be skewed, and this has made it difficult to analyse the sources of variation. We have studied plasma CK in 206 pairs of twins and have analysed the results after separating them into what appear to be two Gaussian frequency distributions. The results in the main distribution (CK < 300 iu/1) are apparently affected by genetic factors common to both men and women, and by environmental factors which are of much greater effect in men. The tendency for some men to have very high CK values may also have a genetic basis.
The Holoacardius: A Correlative Computerized Tomographic, Radiologic, and Ultrasonographic Investigation of a New Case with Review of Literature
Authors: Bhatnagar K.P. , Sharma S.C. , Bisker J.
Published: July 2016

A holoacardius from a monozygotic, monochorionic twin pregnancy of 36 weeks is described. Trisomy-18 was diagnosed in the viable female cotwin. Computerized tomographic, radiologic, and ultrasonographic procedures were applied to the acardiac. Its three-vessel umbilical cord was velamentously attached to the single placenta. Grossly malformed and poorly developed craniofacial structures, absence of neck and upper extremities, sirenomelic lower extremity, absence of heart, and development of only a few skeletal elements were prominent features. A review of selected world literature emphasizes the limits of the estimates dealing with the total number of reported cases and the incidence of acardii.
Monoamniotic Twin Pregnancy
Authors: Lumme R.H. , Saarikoski S.V.
Published: July 2016

The course and outcome of 23 monoamniotic (MA) twin pregnancies, delivered in Tampere University Central Hospital during the years 1964-1984, were studied retrospectively and compared to 1056 diamniotic (DA) twin pregnancies. The frequency of MA twins was 2.1% of twin pregnancies. Polyhydramnion complicated the pregnancy in 26% of MA vs 6% of DA pregnancies. Two cases were defined as acute polyhydramnion. Preterm labour was stated in 70% of MA pregnancies and deliveries before the 34th week were 4 times more common in MA than DA pregnancies. The cesarean section rate was more than double in MA pregnancies (39%). Entanglement of the umbilical cords was noted four times, and prolapse of the cord in three vaginally delivered cases. Perinatal mortality was 28% in MA vs 5% in DA twins. The most common causes of death were respiratory distress syndrome, congenital malformation and feto-fetal transfusion.
The Inheritance of Plasma and Red Blood Cell Magnesium and Zinc Levels Studied From Twin and Family Data
Authors: Darlu P. , Michotte Y. , Defrise-Gussenhoven E. , Henrotte J.G.
Published: July 2016

The variability of magnesium and zinc concentrations in plasma and erythrocytes was investigated by twin and family studies. Twins were sampled in two distinct ways and in two different West-European regions. In one of the samples, a distinction was made between twins living together and twins living apart. Two series of families were studied, one in a homogeneous environment, the other in a more diverse environment. Samples were compared by variance analysis. The results show 1) that genetic variability is significant for red blood cell (RBC) magnesium and zinc, minor for plasma magnesium and absent for plasma zinc; 2) that the family environment affects the extent of resemblance between twins and between siblings more for plasma levels than for RBC levels of magnesium and zinc. Furthermore, the intercorrelation analysis suggests that the genetic regulation systems of RBC magnesium and zinc are different, whereas some of the environmental regulation systems of plasma magnesium and zinc are the same. Biological interpretations are brought forward and discussed.
Matching in Epidemiology as a Paradigm for Twin Research on the Etiology of Disease
Authors: White Colin
Published: July 2016

This article is a review of the technique of matching as it applies to epidemiological investgations of the etiology of disease. It is written for researchers who wish to use twins as the matched pairs in studies of this type.
Four-Year Follow-up of Locomotor and Language Development in 34 Twin Pairs
Authors: Åkerman B. Alin , Thomassen P.A.
Published: July 2016

A group of 34 twin pairs was studied at four years of age. Characteristics of the group were a homogeneous social background, good parental interrelationship and conscientious care during pregnancy, delivery and the neonatal period. All the children were tested with the Griffiths' Mental Development Scales. The girls generally showed a higher development quotient than the boys. Birth weight seemed to be the most important factor; at 4 years of age, the twins with a birth weight of less than 2500 grams had a significantly lower locomotor quotient. The langage quotient showed a similar trend. This difference was, however, not significant. No significant differences in either locomotor or language development could be observed between MZ and DZ twins.
Maternal Reactions to the Birth of Triplets
Authors: Robin M. , Bydlowski M. , Cahen F. , Josse D.
Published: July 2016

This study examines the reactions of 14 women to the birth of triplets. Home interviews and observations were conducted at 4 months and 1 year after the birth. The findings indicate that the triplet situation constitutes a real source of psychological stress for the women in this study. Reactions depend on two factors: individual makeup, in that some women become depressed whereas others develop defenses, and amount of support from family and friends. These variables, along with mothers' ability to overcome phantasms of abnormality generated by the exceptionality of a multiple maternity, serve to define a set of predictors of good/poor prognosis for the establishment of triplet-mother relationships.