bluuebunny/crossref_metadata_2025 huggingface dataset:
What Information Should the Multiple Birth Family Receive Before, During and After the Birth?
Authors: Hay D.A. , Gleeson C. , Davies C. , Lorden B. , Mitchell D. , Paton L.
Published: July 2016

Advances in the management of the multiple pregnancy and delivery must be accompanied by corresponding improvements in service access outside key centres and especially in the information families receive about what may happen during or after the pregnancy. A major review of birthing services in Victoria has focussed attention on four areas where the quality of information is often inadequate. 1) Prepregnancy and the standard of counselling about the incidence of multiples as a result of fertility drugs and in vitro fertilization procedures and about problems which may accompany a multiple birth. 2) Antenatal: At what stage of the pregnancy should parents be told of the multiple pregnancy and how should monitoring of the mother and procedures such as bedrest take into account what are often conflicting demands within the family? 3) Perinatal: Families are frequently illprepared for a cesarean delivery and for the procedures for premature multiples. The problem is often compounded by separation of the mother from one or both twins. While bereavement services are improving, much still needs to be learned about handling congenital abnormalities in one or more multiples. 4) Postnatal: Irrespective of the level of prenatal advice, families greatly underestimate the workload with multiples. The resulting stress contributes to the incidence of postnatal depression, child abuse and divorce now being reported from multiple birth families. Some suggestions are made from social psychology and genetic counselling about how families can best handle risk information to achieve the goal of neither under- nor overestimating the risks at these different stages of the multiple pregnancy.
Twin Children in Volunteer Registries: Biases in Parental Participation and Reporting
Authors: Hay D.A. , Clifford C. , Derrick P. , Hopper J. , Renard B. , Theobald T.M.
Published: July 2016

The biases in volutary participation by adult twins are well known but less attention has been paid to twin children where parents decide on participation and provide much of the information. Several aspects of reporting including the assessment of zygosity are compared in four large Australian data bases: 1) a nationwide compulsory (and hence representative) survey of literacy and numeracy; 2) a nationwide “Twins in School” survey of parents and teachers of twins run through Education Departments and AMBA, the parents organisation in conjunction with LaTrobe; 3) the LaTrobe Twin Study which is a longitudinal program involving frequent interactions between families and researchers, and 4) the Australian NHMRC Twin Registry which has surveyed a large sample of their families with twin children by mail. One potential bias comes when recruitment is on a continuing basis as in the LaTrobe Twin Study and the Australian Twin Registry when differences between “early” and “late” enrolling families arise. One difference between the four samples arose from parents being much more likely to contrast their twins and to report problems in one but not the other, whereas teachers' and psychologists' assessments of these same children generally reported much smaller intrapair differences. Future studies should have some common questions to provide comparative data on such biases. Key questions are proposed for this area, mainly on the perceived need for different forms of remediation, together with other recommendations about the minimal essential baseline data set for a registry.
Study of Gene-Environment Effects on Development of Hyperopia: A Study of 191 Adult Twin Pairs from the Finnish Twin Cohort Study
Authors: Teikari J. , Koskenvuo M. , Kaprio J. , O'Donnell J.
Published: July 2016

The Finnish Twin Cohort material was used to estimate genetic and environmental effects in the etiology of hyperopia (farsightedness). All twin pairs in the cohort born before year 1927 (age 60 years and over at the time of the study), with both members alive, were sent a questionnaire. The questionnaire included questions of past and present eye diseases, visits to ophthalmologists, use of glasses and other vision-related questions. The hyperopia was assessed by asking the patients to send their last prescription for glasses to the authors. Twins with any eye disease affecting refraction (cataract, corneal damage), operation or trauma to their eyes were discarded from the present study. In 191 pairs (80 monozygotic and 111 dizygotic pairs) one or both members of the pair had a hyperopic refractive error. The correlations of refraction between right and left eyes of both MZ and DZ pairs were high (Spearman Rank Correlations of 0.86-0.89). The intrapair correlations among MZ pairs were higher (0.44 for right and 0.45 for left eyes) than intrapair correlations among DZ pairs (0.24 for right and 0.15 for left eyes). The variances were not significantly different among MZ and DZ pairs. The classical analysis of heritability gave an estimate of 0.75 for hyperopia. The result suggests that genetic factors are important in hyperopia and especially in hyperopia of higher degree.
Monozygotic Twin Resemblance in Fatness and Fat Cell Lipolysis
Authors: Després J.P. , Bouchard C.
Published: July 2016

Six skinfold measurements, and percent body fat and fat-free weight derived from the underwater weighing technique were obtained in 43 pairs of male and 44 pairs of female monozygotic (MZ) twins. A fat tissue biopsy was performed in the suprailiac region in 20 male and 16 female pairs in order to determine mean adipocyte diameter and basal lipolysis as well as epinephrine maximally stimulated lipolysis (10−4M). Twin resemblance in body fatness is clearly demonstrated by the analysis of the between MZ sibships over the within MZ shibship means of squares for all skinfold measurements, percent body fat and fat free weight (P < 0.01). Within MZ pair similarity is as high in female as in male pairs for body fatness. Moreover, members of the same twin pair resemble one another significantly for fat cell size and fat cell lipolytic activities, particularly when epinephrine stimulated. In female MZ pairs, additional studies with control over the menstrual cycle are needed to clarify the case of isolated fat cell basal lipolysis.
Estimates of Genetic Variance for Some Selected Morphometric Characters: A Twin Study
Authors: Sharma J.C. , Sharma K.
Published: July 2016

Results on genetic variability in some of the morphometric characters on head and face, body girths and skin folds, based on 45 MZ and 67 like-sex DZ twin pairs, are presented. The data were subjected to a method which eliminated possible biases in the estimated genetic variances that could result from heterogeneity of total variances between zygosities of the 17 head and face measurements, heterogeneity was observed for only bizygomatic diameter. Head breadth means differed between MZ and DZ twins, indicating bias in the trait's genetic variance analysis. The results indicated a significant genetic component in these morphometric traits. For 11 girth and skinfold measurements, the t'-test based on hierarchical structure of twin data, also failed to reveal any appreciable difference between the mean values of MZ and DZ twins. Heterogeneity of total variance between zygosities was observed for three skinfold measurements, ie, biceps, triceps and suprailiac. The girth measurements, however, did not reveal any heterogeneity of total variances between the zygosities. The estimates of genetic variance revealed stronger genetic component for the girths than for the skinfolds.
Toward a Theory of Human Multiple Birthing: Sociobiology and r/K Reproductive Strategies
Authors: Rushton J. Philippe
Published: July 2016

Using symbols from population biology, a continuum of reproductive strategies can be distinguished ranging from r, the production of large numbers of offspring provided with minimal care, to K, the production of few offspring nurtured intensively. While all humans are at the K end of the continuum, some are proposed to be more so than others. If multiple egg production is part of an r-reproductive strategy, certain facts may be ordered. Compared to mothers of singletons, for example, mothers of DZ twins nave a lower age of menarche, a shorter menstrual cycle, a higher number of marriages, a higher rate of coitus, more illegitimate children, a closer spacing of births, a greater fecundity, more wasted pregnancies, a larger family, an earlier menopause, and an earlier mortality. Further, all twins have a shorter gestation period, a lower birth weight, and a greater incidence of infant mortality, with DZ twins having a greater frequency of health disorders, a higher mortality rate, and a lower rate of enrollment in volunteer registries. Multiple birthing also occurs more frequently in families of lower than of higher social status, and in those of African than of European and especially than of Orientai descent.
The Recent Trends in Multiple Births and Stillbirth Rates in Japan
Authors: Imaizumi Y.
Published: July 2016

The twinning rate remained nearly Constant up to 1968, then decreased in 1974 and gradually increased with the year. The triplet birth rate remained nearly Constant up to 1974, then increased up to 1982, where the rate was 1.8 times higher than in 1968, and decreased thereafter. On the other hand, the quadruplet birth rate remained nearly Constant up to 1968, was eightfold in 1975, then decreased until 1984 and suddenly increased to 8 per million births in 1985. The higher multiple birth rates since 1974 was attributed to the higher proportion of mothers treated with ovulation-inducing hormones in Japan. The stillbirth rates decreased to 2/5 for male twins and to 1/3 for female twins during the 25-year period from 1960, to 2/5 for triplets and to 1/5 for quadruplets during the 34-year period from 1951.
Excessive Twinning in a Rural American Genealogy: The Demographic Pedigree
Authors: Sheets John W.
Published: July 2016

Excessive twinning in an extended family of rural Missouri concentrates in the isolated generations of 1874-1930s. Moderate inbreeding, larger sibships to older mothers, and access to local doctors may have combined to enhance this familial twinning. These biosocial factors are similar to an isolated case of excessive twinning in Scotland.
Twinning in New England in the 17th–19th Centuries
Authors: Miura T. , Kawana H. , Nonaka K.
Published: July 2016

Vital records of Saybrook and Plymouth in New England from the 17th century were investigated. Among 8,562 maternities 81 twin maternities were found, the twinning rate being 0.95%. Twinning rate was low at the lst and 2nd births as compared with the 3rd or later births, and was highest at the 7th and 8th births (1.6%). Twin maternity seemed to be a strong risk factor to terminate reproduction, particularly after 6 or more children had been delivered. The rate of mothers who had any other child (“fertile” mothers) at the 7th or later birth order was significantly lower for twin (13%) than for singleton maternities (63%). Twinning rate also varied by the size of offspring of a mother, and those mothers who had 5 or 6 children showed the highest twinning rate (1.3%). Those fertile mothers who had 7 or more children showed the lowest twinning rate (0.74%), although an exceptionally higher twinning rate was seen at their last births. Elongation of the last birth interval was observed for each group of every family size, and higher twinning rates were generally observed at their last births. Reduction in fecundity and rise in twinning rate seem to have occurred simultaneously at the last stage of the reproductive period of mothers, regardless of their family size.
Alternate Changes in Birth Seasonality of Twins During 1971–1984 in Japan
Authors: Nakamura I. , Amau Y. , Nonaka K. , Miura T.
Published: July 2016

Birth dates of 1,536 twin-pairs in 1971-1984 were collected from the members of an association of twins' mothers. The seasonal variation of twinning changed every 2-4 years. Years when twinning rate was higher in the summer-fall season (1971-72, 1976-77, 1982-84) and those when a peak of the rate was not observed (1973-75, 1978-81) appeared alternately. In years with a summer-fall peak, the elevation of twinning in the summer-fall season was detected consistently in both like- and unlike-sexed and in both MZ and DZ twin groups. The twinning seasonality in these years, however, was not evident in twin births of mothers who were born in May-July. These results suggest the possibility that seasonal factors which influence the twinning rate be not multiple-ovulation-inducing but probably abortion-inducing factors and most likely seasonally epidemic microbes.
Cyclic Variations of Twin Births at Isle-aux-Coudres: A Case/Control Approach
Authors: Philippe P.
Published: July 2016

Twins and singletons were matched for several confounding factors. The monthly distribution of twin births and that of singleton births were compared with a uniform allocation of births over the year. Opposite seasonal variations emerged that were confirmed by a case/control comparison. Twins occurred more often in winter and early spring while singletons proved to be relatively few; singleton peaked in the fall season when the risk of a twin birth was low. These trends held across maternal age at birth and the time period of birth. Results suggest that the conception of a twin pair is higest in spring and early summer and lowest in winter. The role of sunlight in the twinning liability is discussed along with the role of sexual intercourse. That twin-prone mothers are usually more fecund in spring and early summer is a distinct possibility.
Serial Amniocenteses in the Treatment of Twin to Twin Transfusion Complicated with Acute Polyhydramnios
Authors: Feingold M. , Cetrulo C.L. , Newton E.R. , Weiss J. , Shakr C. , Shmoys S.
Published: July 2016

Twin to twin transfusion, complicated by acute polyhydramnios in a monozygous twin pregnancy, is a difficult clinical problem. A precipitous course usually results in termination of the pregnancy within a few days and often is associated with a high perinatal mortality rate. Two cases are presented that were treated with repeated amniocenteses for the relief of extreme abdominal discomfort and to prevent imminent premature labor. The amount of amniotic fluid removed each time varied from 300 cc to 1200 cc, which was enough to relieve symptoms but not enough to induce uncontrolled uterine activity. A total of 3500 cc and 4750 cc of amniotic fluid were removed from the first and the second patient, respectively. The procedure was found to be safe and resulted in prolonging the pregnancies by 14 and 11 days, respectively. This management, with the addition of tocolysis and close fetal surveillance can offer some hope in an otherwise hopeless situation.
Social Cost of Twin Births
Authors: Papiernik Emile
Published: July 2016

This study analyzes costs for neonatal care and costs for care of handicapped children related to twin pregnancies and births. These costs are highly related to the unfavorable birthweight distribution for twins. Each twin pregnancy may cost 10 times more than a single pregnancy. This economic analysis favors all kinds of preventive policies and a calculation is proposed for measuring the probable effect in costs of even a slight decrease in the proportion of very low and low birthweight for twins.
Inheritance and Alcohol as Factors Influencing Plasma Uric Acid Levels
Authors: Whitfield J.B. , Martin N.G.
Published: July 2016

Variation in plasma uric acid levels in 206 pairs of male and female twins, aged from 18 to 34 years, was consistent with a simple model including only individual environmental and additive genetic effects and a heritability of h2= 0.73. Individual environmental variation was estimated to be approximately the same as variation of individuals measured on two occasions. Correlations of DZ pairs were also consistent with sex-linked genetic effects. In men there was a significant genetic correlation with weekly alcohol consumption and as much as 18% of the variation in uric acid levels could be accounted for by genetic variation in alcohol consumption.
Isoagglutinin Levels in Twins and Families. A Study of the Inheritance of Naturally Occurring Antibodies in Human Serum
Authors: Agrawal S. , Bhalla V.
Published: July 2016

Anti-A and anti-B titers were measured in 60 twin pairs and their families. Family data shows high correlations of antibody titer values for first degree relatives but no significant spousal correlations.
A Genetic Analysis of Taste Threshold for Phenylthiocarbamide
Authors: Morton C. C. , Cantor R. M. , Corey L. A. , Nance W. E.
Published: July 2016

Taste threshold for phenylthiocarbamide (PTC) was measured in 393 offspring from the families of 85 monozygotic (MZ) twin pairs. PTC scores were bimodally distributed with modes at one and eight and the antimode at five. Because of the non-normality of the distribution, a jackknife procedure was used to obtain 95% confidence intervals for the estimates of genetic, maternal, and environmental parameters. Analyses which assumed no epistasis and which included additive genetic effects revealed that 37.9% of the observed variation in PTC threshold was due to additive genetic effects, 16.6% was due to dominance effects, 14.2% was due to maternal effects, 13.7% was due to a common sibship environment, and 17.6% was due to random environmental effects, yielding a broad sense heritability of 0.55 for the threshold ability to taste PTC. Analyses which did not include additive genetic effects revealed 26.6% of the observed variance was due to dominance effects, 23.6% to maternal effects, and 49.8% to environmental effects at the 0.67 confidence levels, but that environmental factors accounted for 72.4% and dominance effects for 23.6% of the observed variation at the 95% level.
Spontaneous Drawing and the Individuality of Twins
Authors: Gedda L.
Published: July 2016

Only rarely have geneticists, neurobiologists and psychologists availed themselves of twins for the study of the human mind's individuality. I believe, on the contrary, that twin data represent an invaluable means of research also for phenomena connected with human individuality and the functioning of the nervous system.

To this end I thought of having MZ and DZ twins take a creativity test by means of spontaneous drawings of a single subject applied to individual MZ and DZ twin pairs.

The preselected twins totalled 31 MZ and 13 DZ pairs of an age span during which the twins live together and experience the same environmental influences.

The creativity test I devised consists of asking the twins to make a drawing of the family mealtime scene at which they all participate. The drawings were to be made on identical pieces of white paper, selecting colors from the same box of colored pencils given to each of them. When the test was explained, each twin was placed in a different room with no possibility of communication, and was asked to make the drawing, supervised at a distance by an assistant.

In order to analyze the drawings, I established ten parameters: 1) First impression at a glance; 2) Choice of colors; 3) Choice of perspective; 4) Choice of persons' positions; 5) Emphasis on twins; 6) Shape of table; 7) Table settings and food dishes; 8) Room furniture; 9) Drawing of building; 10) Landscape.
Twins: Are They at Risk? A Longitudinal Study of Twins and Nontwins from Birth to 18 Years of Age
Authors: Åkerman B. Alin , Fischbein S.
Published: July 2016

The purpose of this study has been a comparison of a group of twins (145 pairs) and a whole cohort of singletons (114,828 individuals) born 1953 and living in the Stockholm metropolitan area in 1963. The twins and singletons have been followed from birth onwards. A pertinent question is whether twins are at greater risk at birth and whether they are predisposed to below-average mental and physical growth. The results show that twins are more susceptible to lower birth weight, shorter gestation period and birth complications. These factors also seem to have a lasting effect on later physical and mental development. Monozygotic twins, twin girls, and male twins with low birth weight, seem to be particularly at risk for below-average mental and physical growth. An interaction between social background and birth weight can also be seen for the male twin group.
Gestational Age-Specific Birthweights of Twins Versus Singletons
Authors: Luke B. , Witter F.R. , Abbey H. , Feng T. , Namnoum A.B. , Paige D.M. , Johnson T.R.B.
Published: July 2016

In order to more adequately characterize patterns of intrauterine growth retardation in twins, the mean birthweights of all nonanomalous white or black twins born between 24 and 41 weeks of gestation and surviving until discharge over an 11-year period (547 infants) and all similar singletons (19,072 infants) were compared by completed weeks of gestation. Between 24 and 35 weeks of gestation, the mean birthweights for the 547 twins and the 19,072 singletons were comparable and did not consistently differ statistically. From 36 to 41 weeks gestation, however, the difference became large, consistent, and statistically significant for each week at P < 0.0001. This difference was present among all subgroups of twins, ie, in all males, females, blacks, and whites; it was still evident when the sample was further stratified by both race and sex (black males, white males, black females, white females). These data suggest a pattern of growth retardation in twins compared to singletons which is large, consistent, and statistically significant beginning at 36 weeks gestation. Clinically, these data also suggest the need for ultrasonic examination early in gestation (24-32 weeks) to document normal growth and to provide baseline data, and show the importance of such monitoring later in gestation, specifically after 36 weeks.
Blood Pressure Discordance and Lifestyle: Japanese Identical Twins Reared Apart and Together
Authors: Hayakawa K. , Shimizu T.
Published: July 2016

A total of 198 pairs of monozygotic twins reared apart and together were surveyed on their lifestyle and blood pressure through mailed questionnaires. The age of the subjects ranged from 47 to 87 years. The intrapair concordance rate on blood pressure increased from 51% (age of separation 0-5) to 78% (age of separation 26 and over) as the age of separation advanced. The concordance rate on occupation was 59% at the age of separation 0-5 and 87% at the age of separation 26 and over. The intrapair concordance on the food intake (egg, meat, fish, milk and salty seasoning) was positively correlated with the age of separation. Hayshi's quantification theory III (multivariate analysis) was used to claryfy the lifestyle pattern in 39 MZ pairs discordant on blood pressure. There were three factors (meat, milk and occupation) which were closely related with each other in the “non-hypertensive” twins, while lifestyle were not patterned in the “hypertensive” twins. The concordance rate of these three items increased along with the rise of concordance rate of blood pressure as the age of separation advanced.
Cardiovascular Reflexes in Monozygotic Twins Discordant for Exposure to Organic Solvents
Authors: Matikainen E. , Juntunen J. , Koskenvuo M. , Antti-Poika M. , Kaprio J.
Published: July 2016

Eighteen pairs of monozygotic twins discordant for long-term occupational exposure to organic solvents were examined for disturbances of cardiovascular reflexes. All of the subjects were asymptomatic, and considered themselves healthy. No significant differences were observed between the exposed and the nonexposed twins. The finding suggests that occupational solvent exposure at these particular levels is unlikely to cause disturbances of the autonomic nervous function.
Twin Study on Myopia
Authors: Lin L.L.-K. , Chen C.-J.
Published: July 2016

In order to reassess the relative importance of genetic and environmental factors in the development of myopia in Chinese schoolchildren, 90 pairs of MZ and 36 pairs of like-sex DZ twins were enrolled for detailed ophthalmological examination about their ocular refractions. Corneal curvatures and axial lengths were also measured. With equivalent settings of the range for concordance, corneal curvatures showed higher concordance rate (84%) than ocular refractions (65%) and axial lenghts (59%) in MZ twins. F-test on the intrapair variances between MZ and DZ twins revealed a significant hereditary role in determining the ocular refraction and its optical components. The degree of genetic determination was expressed by heritability indices, which were derived from intraclass correlation coefficients. The diversity of sample ages and refractions, while making the obtained data difficult to further explore the gene-environment interaction, led to the observation of more intrapair differences with age and myopic progression in MZ twins.
Atrial Activity and Cardiovascular Response to Stress in Triplets: Short Case Report
Authors: Campbell S. Villatico , Maio F. Di , Scioli A. , Sciacca A. , Brenci G. , Gedda L.
Published: July 2016

Using high-resolution electrocardiography (HRE), we have previously examined the morphological aspects of the atriogram in a set of DZ triplets comparing the MZ and the DZ pairs [3]. We now repeated the recordings on the triplets, three years after the first studies, in order to evaluate the individual morphological reproducibility of the atriogram and the cardiovascular response to effort and to stress by means of provocative tests [1-3].

We studied a set of female DZ triplets aged 15 years, born normally at the 39th week of gestation, with two chorions and three amnions. We compared the responses to the individual provocative tests, and repeated the analysis of the atriograms after three years. We therefore used the HRE, the Bruce protocol ergometric test, and the sympathetic stimulation tests: handgrip test, cold pressure test, arithmetic mental test (Table).
Teratomorfism in the Urinary Tract of MZ Twins: Short Case Report
Authors: Gedda L. , Brenci G. , Laurenti C. , De Dominicis C. , Mattioli D.
Published: July 2016

A case of 15-years old, Roman male twins affected by balanic hypospadia is reported. Previous corrective surgery had not been satisfactory, leaving both boys with a curvature of the last portion of the penis. Urographic examination, carried out upon presentation, revealed in both patients a mirror renal ectopy with fusion of the two kidneys. In both, the displaced malformed kidney is below the normally situated one. In depth examination shows: 1) that the malformation concerns not only external genitals but also internal urogenital organs because of the monolateral ectopy of the normal kidney and the malformation of the ectopic kidney in both twins; 2) that the twins are MZ and that their teratological specularity is biologically of interest.

Specularity, or mirror imaging, is a well known phenomenon in twins, particularly MZ twins. It may involve slight forms, such as handedness, or rare forms, such as those involving single organs, like the heart, which can be on the left side in one twin and on the right in the MZ cotwin. That must occur in the early embryogenetic stages, and various environmental and genetic factors may be involved. In particular, one can speculate that genetic variations in cell-adhesion molecules (CAM) and/or the late time of splitting of the conceptus to originate the two twins, may all play a role.
Finnish Twins Reared Apart III: Personality Factors
Authors: Langinvainio H. , Kaprio J. , Koskenvuo M. , Lönnqvist J.
Published: July 2016

This study is based on data from 165 adult twin pairs separated at 10 years or less. Information on personality factors: extraversion (E) and neuroticism (N) (EPI scale short from), life satisfaction (LS) (Allardt) and stress of daily activities (SDA) was obtained as part of the questionnaire study carried out in the entire Finnish Twin Cohort in 1975. Later in 1979 a questionnaire sent to the twins reared apart yielded a scale (range 7-30 points) measuring the environmental dissimilarities after separation (reliability 0.83). The effect of separation on personality factors by analysis of variance of individual data was studied. Sex, zygosity and age-at-separation were included in the models. The overall expalanatory rates were low (2.1-4.4%). The definitive study group was formed by selecting those pairs with a dissimilarity score greater than 15. The following intraclass correlations were obtained:
Psychiatric Hospitalization in Twins
Authors: Koskenvuo M. , Langinvainio H. , Kaprio J. , Lönnqvist J. , Tienari P.
Published: July 2016

Hospitalization rates of monozygotic (MZ) and dizygotic (DZ) twin pairs in Finland were compared for schizophrenia, neuroses, and alcoholism. Record-linkage of hospital records and death certificates for the years 1972-1979 was carried out for persons in the Finnish Twin Cohort (16,649 like-sexed twin pairs). The ratio of the number of observed vs that of expected concordant pairs and the ratio of concordance rates between MZ and DZ pairs were greater among males than females, and greater among young (40 years old or less) than among older pairs. The highest difference was found in schizophrenia and the lowest in neuroses. Pairwise concordance rates for schizophrenia (11.0% for MZ and 1.8% for DZ) seem to indicate great environmental influence (high proportion of discordant pairs) with apparent genetic liability (6.1-fold ratio in concordance between MZ and DZ pairs). In neurotic disorders, the difference of pairwise concordance rates between MZ and DZ pairs (6.8% vs 4.0%) was quite low, not strongly supporting a genetic hypothesis. Of the MZ pairs concordant for psychiatric hospitalization, 47% had lived together for their whole life time; of those discordant, 16% lived together. The corresponding figures for DZ pairs were 18% and 15%. The effect of intrapair relationships in disease-concordant pairs should be taken into account when evaluating the effect of genetic and environmental factors in psychiatric disorders.
Presidential Address: The Aberdeen Contribution to Twinning
Authors: MacGillivray Ian
Published: July 2016

Although Francis Galton was the first to use twins for comparative genetic studies in a scientific way, there had been considerable interest and speculation about twinning from very early times. This has been referred to in numerous publications in the past, and indeed, Professor Gedda, Founding President of our Society, has written extensively on this [9]. The earlier writings referred almost entirely to the twins themselves, and there seemed to have been little attention paid to the mothers, except that they were either considered to have had intercourse with two men, or indeed, with a deity. Galton also referred in his publication of 1876 [8] to the largeness of the families into which twins are born, but a graduate of Aberdeen University, James Matthews Duncan, had pointed out some of the characteristics of mothers having twins ten years earlier. In 1865 he published his paper “On the Comparative Frequency of Twin-Bearing in Different Pregnancies” [7] and in this he showed that mothers of twins tended to be of higher parity and older. This very accurate observation has since been confirmed, but is was not clear whether age and parity were separate factors until Anderson, again working in Aberdeen, showed in 1956 that the twinning incidence increased up to a peak at age 35 and thereafter fell [1].
Factors Contributing to a Reduction of Twin Perinatal Mortality in Singapore
Authors: TambyRaja R.L. , Ratnam S.S.
Published: July 2016

A total of 204 cases of twin pregnancy occurred between 1970 and 1972 have been compared with 102 cases occurred between 1976 and 1978. During the interval of time, specialised care was instituted for the early diagnosis and management of twins. The incidence of twin pregnancy in Singapore decreased from 1:131 to 1:141 pregnancies. With a background of improved socioeconomic conditions and obstetric care, there has been a dramatic decline in perinatal mortality from 76.4 to 29 per 1000. In undiagnosed cases, the perinatal mortality of the first vs the second twin in the earlier group was 64.4 vs 93.6 per 1000. No such difference was observed in the later period, with the average birthweights of twins being significantly higher. The principles of our antenatal supervision, antenatal tocography, and management are presented and the value of early diagnosis, bedrest, and tocolytic therapy discussed. The reduced perinatal mortality and mobidity gives evidence of an improvement in prematurity and augmented intrauterine growth.
Fetoscopy in the Management of Twin Pregnancies Discordant for a Severe Abnormality
Authors: Rodeck C.H.
Published: July 2016

Selective feticide by fetoscopic air embolism was carried out in six twin pregnancies complicated by discordance for a severe abnormality. In three, a previous diagnostic fetoscopy had been performed. The procedure was effective and uncomplicated in all cases. One patient is undelivered and five have delivered healthy babies, three at term and two preterm. One of the latter, delivered at 28 weeks, died of complications in the neonatal period.
Twinning Rates and Seasonal Changes in Görlitz, Germany, from 1611 to 1860
Authors: Richter J. , Miura T. , Nakamura I. , Nonaka K.
Published: July 2016

Old-age twinning rates were evaluated over a period of 250 years (1611-1860), from 80,256 parish records of baptism in a church office in Görlitz, East Germany. Two periods with high and two periods with low twinning rates were observed. Twinning rates were relatively stable in spring and fall, but varied greatly in winter and summer.
Gonadotropin Levels in Mothers Who Have Had Two Sets of DZ Twins
Authors: Martin N.G. , El Beaini J.L. , Olsen M.E. , Bhatnagar A.S. , Macourt D.
Published: July 2016

Serum gonadotropin, estradiol, prolactin and alpha-1-antitrypsin levels were measured in the first four days of the menstrual cycle in 14 women who were cycling normally. FSH, and to a lesser extent LH levels, were significantly higher in a group of 8 women who had at least one set of DZ twins (6 of whom had 2 sets) than in a control group of 6 women with no DZ twins. Estradiol levels also tended to be higher in mothers of twins but there were no significant differences in prolactin or alpha-1-antitrypsin concentrations. There were no differences between the means of the two groups in age, height, weight or number of pregnancies.
Health Characteristics of Mothers of Twins
Authors: Wyshak Grace
Published: July 2016

Mothers of twins, as compared with mothers of singletons, are taller, and for a given height are heavier; they have slightly earlier menarche and menopause. Our recent studies have shown that mothers of DZ twins are at greater risk of cancer of the pancreas (but not for cancers of other sites), as well as of death due to diabetes, other endocrine diseases, and allergies. These findings are consistent with the clinical and epidemiological literature. We have also found that singleton siblings of twins are slightly heavier at birth than children born into sibships consisting of singletons only. The need for further research on the characteristics and long-term health of mothers of twins is indicated.
Genetic Models of Affective Disorder: Application to Twin Data
Authors: Baron Miron
Published: July 2016

Twin data on bipolar and unipolar affective disorders are analyzed by multiple threshold models of inheritance. The two illness types are represented in the models on a continuum of genetic–environmental liability in which bipolar illness has a higher liability threshold than unipolar disorder. Autosomal single major locus model provides an acceptable fit to observed concordance rates in monozygotic twins. The multifactorial-polygenic model is rejected.
Reduction of Main Line C
Authors: Vormittag Walter , Weninger Margarete
Published: July 2016

Fifteen hundred palmar prints of normal persons and patients suffering from various diseases were studied and classified as to dermal ridge configurations at the base of digit IV, after the exclusion of main line C courses with endings at one of the palmar marginal regions. This classification scheme, based on the three classical reduction forms of line C (O,X(8),x), resulted in the differentiation of three main groups, A, B, and C. Within these main groups, pattern types with strong similarity were combined to subgroups allowing an easier documentation. Twin and family data were used to test whether the described pattern types, besides the classical abortive states O,X and x of line C (called special and intermediate forms), are heritable and for which of them a remarkable reduction tendency could be established. The results allow us to confirm the main grouping and the assumed reduction tendency of the special forms of group A.
Perinatal Mortality in Twins
Authors: Chaurasia A. R.
Published: July 2016

Perinatal mortality in twins is found to vary widely in six developed countries for which national data are available. The influence of factors such as birth weight, maternal age, and parity is examined, but no consistent trend is found.
The Vanishing Twin
Authors: Landy Helain J. , Keith Louis , Keith Donald
Published: July 2016

In general, it has not been recognized that many twin or multiple gestations are lost in utero early in pregnancy. Until the advent of ultrasound, the ability to document early human fetal loss in multiple gestation was difficult. However, recent reports of serial ultrasound examinations of pregnant women have documented the “disappearance” of at least one of two gestational rings. Furthermore, the number of twins observed at delivery was significantly less than the number of twin conceptions originally identified by ultrasound during the first trimester. These observations led to the concept of the “vanishing twin” [8,10,13,15,17,20,22,35,41].

In order to obtain reference and personal data on this subject, we reviewed the literature and corresponded with members of the International Society for Twin Studies and obstetricians affiliated with Northwestern University Medical School, Chicago, Illinois. The nine studies that have documented this phenomenon cite “disappearance” rates ranging from 0% to 78%, depending on patient population and timing of ultrasonography [8,10,13,15,17,20,22,35,41]. Several explanations are offered: physiological mechanisms of “disappearance” (resorption or formation of a blighted ovum or fetus papyraceus), artifactual error, incomplete scanning technique, and poor quality ultrasound equipment. The only complication thus far associated with “disappearance” of a fetus is slight vaginal bleeding.
Uterine Height and Umbilical Perimeter Curves in Twin Pregnancies
Authors: Leroy B. , Lefort F. , Jeny R.
Published: July 2016

From previous research, which gave standard curves for the evolution of uterine height and umbilical perimeter according to gestational age in the case of single pregnancies, the authors propose curves which show the variations of these two parameters in twin pregnancies.

The observed differences are sufficient to allow a diagnosis of twin pregnancy as soon as the 18th week of amenorrhea.

This observation is interesting because, until now, a systematic early B-scan examination has not been performed as a rule.
Ultrasonic Evaluation of Twin Pregnancies Associated With Raised Serum Alpha-Fetoprotein Levels
Authors: Neilson J.P. , Hood V.D. , Cupples W.
Published: July 2016

Five cases of twin pregnancy associated with elevated maternal serum alpha-fetoprotein levels are presented. In each instance an abnormality was detected by ultrasound examination—in four cases this represented anomalous development of one or both fetuses: discordant anencephaly; a monozygotic heterokaryotypic twin pregnancy with coexistent Turner's syndrome and intrauterine death; concordant body-stalk syndrome; and fetal exomphalos together with an acardiac monster. In the remaining case, there had been an intrauterine death of one of the twins. Ultrasound examination proved valuable in all instances; three pregnancies were terminated and single healthy infants were delivered from each of the other two pregnancies.
Maternal Factors Associated with Small-for-Dateness Among Twins
Authors: Hemon Denis , Berger Colette , Lazar Philippe
Published: July 2016

The maternal risk factors that correlate with small-for-dateness among twins have been analyzed using a sample of 659 twin pairs and a matched sample of singletons. Non-marital status, job involvement, and the previous delivery of a low-birth weight (<2,500g) infant present a negative interaction with twinning, as low gestational age-adjusted birth weight does not correlate significantly with these risk factors among twin gestations, while it does among singleton gestations. On the other hand, the effects of parity, habitual maternal weight, smoking during pregnancy, and twinning are additive on gestational age-adjusted birth weight. Indeed, the decrease in adjusted birth weight associated with these risk factors is of the same magnitude among twins and singletons and is statistically significant in both cases. These findings suggest that exposure of twin pregnancies to these latter risk factors, and particularly to smoking during pregnancy, can lead to the delivery of newborns with extremely low birth weights.
Heritability of Motor Skill
Authors: Williams L. R. T. , Gross J. B.
Published: July 2016

A total of 22 monozygotic (MZ) and 41 dizygotic (DZ) twin pairs were given 72 trials on a stabilometer balance task over six days to study the extent of the genetic contribution to learning and performance of a gross motor skill. The expectations that interindividual differences would be less for the MZ than for the DZ twins and that intraindividual variability would not be different between the two groups were supported. Intraclass correlations were used to provide estimates for the proportions of total phenotypic variance accounted for by heritability (h2), systematic environmental variance (E2), and nonsystematic environmental effects (e2). Heritability was found to be low during the early stages of learning, before it increased to stabilize at approximately 65% for the remaining practice. E2 was highest during these early stages (24%), then declined quickly to stabilize at half that level. Error variance (e2) constituted the remaining variance. Learning profiles of the twin pairs were also analyzed, with a greater intrapair resemblance being found for the MZ twins. The present findings indicate that, for gross motor skills, there is considerable potential for influencing both the levels of performance (and learning) and the differences between individuals by judicious use of systematic environmental effects.
Susceptibility to Motion Sickness
Authors: Sharma Krishan
Published: July 2016

A sample of 119 pairs of twins, together with their 87 siblings and 100 pairs of parents, were examined with respect to susceptibility to the motion sickness syndrome. Children were found to exhibit resistance to the syndrome below two years of age, and females were more susceptible than males. The incidence appeared to be highest in families with both parents affected. Concordance rates were much higher in MZ (100%) than in DZ pairs (27.6%). Genetic effects are likely, but cultural factors should not be ignored.
The Use of Sequential Analysis to Improve the Efficiency of Co-twin Control Studies
Authors: Christian J. C. , Yu P. L. , Grim C. E. , Norton J. A.
Published: July 2016

The co-twin control model using paired-comparison analysis provides an extremely powerful and cost-effective experimental design for clinical research. This paper suggests the possibility of using sequential analysis to further increase the efficiency and specificity of cotwin control studies.
The Northwestern University Multihospital Twin Study. II. Mortality of First Versus Second Twins
Authors: Ellis R.F. , Berger Gary S. , Keith Louis , Depp Richard
Published: July 2016

The results of a multihospital study involving a total of 588 twin pairs born in Chicago in 1970–1975 are reported, with special respect to differences in mortality between first and second twins by time as well as by cause of death. Mortality was higher in second than in first twins and most commonly occurred after delivery and was the result of immaturity and of respiratory distress syndrome.
A Twin Methodology for the Study of Genetic and Environmental Control of Variation in Human Smoking Behavior
Authors: Crumpacker David W. , Cederlöf Rune , Friberg Lars , Kimberling William J. , Sörensen Stefan , Vandenberg Steven G. , Williams James S. , McClearn Gerald E. , Grevér Britt , Iyer Hari , Krier Margaret J. , Pedersen Nancy L. , Price Richard A. , Roulette Ingegärd
Published: July 2016

A method is presented for partitioning the variance associated with human smoking behavior into additive genetic, nonadditive genetic, prenatal environmental, postnatal familial environmental, and postnatal extrafamilial environmental components. Estimations can also be made of additive genetic and residual correlations between spouses and of the correlation between parental additive genetic effect and progeny nonadditive genetic and environmental effect. The variance estimates are free of the biases that might result from these correlations. The statistical genetic analysis is being applied to a large group of MZ and DZ twins, their spouses, and their adult children who live in southern Sweden. Blood samples from each subject will be used to identify their genetic constitution for a number of biochemical polymorphisms, some of which may be considered a priori to have possible relationships to smoking. Associations and genetic linkages between biochemical marker loci and quantitative behavioral traits will be sought. Traits of interest include a wide array of tobacco-use variables, motives for smoking, personality and cognitive variables, and other variables associated with drug use and health. Zygosity determinations based on biochemical polymorphisms have indicated MZ to DZ and DZ to MZ misclassification rates of 0% and 6.15%, respectively, when based solely on external morphology and questionnaire data. The nonpaternity ratio of the fathers with respect to their supposedly biological children is estimated to be 0.28%. Gene frequency estimates for 21 marker loci show that the sample of twins and their relatives is quite representative of the Swedish population at large. All loci were in Hardy-Weinberg-Castle equilibrium, with no evidence of assortative mating for biochemical traits. The MZ twins are significantly more concordant than the DZ twins with respect to whether they have ever had a smoking habit.
Sleep and Dream Characteristics in Twins
Authors: Gedda L. , Brenci G.
Published: July 2016

A study of sleep and dream characteristics has been carried out by questionnaire on a sample of 77 MZ and 76 DZ same-sex twin pairs of two age groups, 6–8 and 16–18 years. Genetic effects could not be detected in the younger age group and appeared to be rather limited in the older one, possibly as a result of the limited variability of the considered variables and of the levelling influence of the common environment.
Dependency of Concordance Probability on Gene Frequencies in Genetic Systems for the Diagnosis of Twin Zygosity. A Graphical Presentation Enabling the Rapid, Optimal Choice of Genetic System
Authors: Sarna Seppo , Kaprio Jaakko
Published: July 2016

The dependency of probabilities of phenotypic concordance of gene frequencies in three-allele genetic systems is presented. A graphical display enables the rapid comparison of the relative effectiveness of different systems, taking into account dominance relationships within each genetic system. Four or more allele systems can also be approximated, while two-allele systems are considered to be special cases of three-allele ones.