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.

A specific prenatal care program is proposed to prevent preterm deliveries in twin pregnancies, with ultrasound scanning, early work leave and home visits by midwifes. A four-year study has been conducted on 197 pregnancies (160 early followed and booked and 37 late referred). It can be shown that early preterm births and very low birth weights are less frequent in the followed group than in published data, as well as in the late referred pregnancies. The total perinatal mortality rate is 25.6 per 1000 total births.

Three questionnaires measuring altruistic tendencies were completed by 573 adult twin pairs from the University of London Institute of Psychiatry Volunteer Twin Register. The questionnaires consisted of a 20-item Self-Report Altruism Scale, a 33-item Empathy Scale, and a 16-item Nurturance Scale, all of which had previously been shown to have construct validity. For the three scales, the intra-class correlations for the 296 MZ pairs were 0.53, 0.54, and 0.49, and for the 179 same-sex DZ pairs were 0.25,020, and 0.14, giving rough estimates of broad heritability of 56%, 68%, and 72%, respectively. Maximum-likelihood model-fitting revealed about 50% of the variance on each scale to be associated with genetic effects, virtually 0% to be due to the twins' common environment, and the remaining 50% to be due to each twins' specific environment and/or error associated with the test.

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

Analysis of mental and motor tests scores and intelligence test performance of twins born in the Collaborative Perinatal Project shows that twins perform more poorly than singletons from the same population and that the differences are greater in Negroes than in whites. The poor performance of twins relative to that of singletons is of complex etiology. It is partly due to poor prenatal environment, for twins brought up as singletons perform at the intelligence level of twins and not of singletons. It may also be partly due to the higher incidence of congenital malformations in twins, especially those of the central nervous system. But the performance of twins, relative to that of singletons, tends to improve as they get older, at least from 4 to 7 years, suggesting that prematurity is also a contributing factor, whose detrimental effects may be reversible.

A mongoloid girl with low-grade idiocy, the 10th of 12 children out of a very poor herds-mans' family in an isolate prealpine place of western Switzerland, was examined at the age of 28. Her mother is recovered on account of schizophrenia (catatonia tarda) as 4 of her (the probands) are feebleminded brothers.

At 21 and 23 years of age the mongoloid proband gave birth to a mongoloid daughter and a mongoloid son; while the latter died of bronchopneumonia when 17 months old — the diagnosis of his mongolism having been ascertained by a pediatrician the first was seen by the author at age 7. The mongolism of mother and daughter is shown by several photographs and by palm and sole prints.

The father of the 2 mongoloid children is most probably the probands' next old brother, a non mongoloid, but highly imbecille.

Procedures are described for the acquisition and analysis of data in a study of the dental and facial characteristics of South Australian twins. Comparisons of the mesiodistal diameters of maxillary incisors in MZ and DZ twins revealed heterogeneity of total variances and evidence of inequality of mean values for some dimensions between MZ and DZ twins. Previous estimates of heritabilities for tooth size, relying on classical assumptions in twin research, may be exaggerated. A preliminary analysis of facial shape was undertaken using a procedure for shape matching based on a least squares fit of homologous coordinates. There was evidence of mirror-imaging in some MZ twin pairs and differences in facial asymmetry between male and female DZ twins. Future extensions of the study using methods for three-dimensional shape analysis are described.

Sixteen anthropometric measurements were performed on each of 48 MZ and 51 DZ adult twin pairs. The largest amount of diversity between MZ and DZ was observed in relation to stature which was in average about three-and-a half times more different in the latter. Forehead and nasal height were also three times more variable among DZ twins, while head and nasal breadth, morphological face height, and lip thickness were twice as variable. The heritability estimates and F ratios yielded significant values in both sexes for twelve traits. The exceptions were mandibular and minimum frontal breadth, calf and chest circumference. The largest heritabilities were observed for stature, head breadth and lip thickness. Correlation matrices were obtained for all measurements; those showing significantly positive coefficients, however, did not show similar heritability values.

The WHO Meeting of Investigators on Methodology of Twin Studies was held in Geneva from 24 October to 1 November 1965. The meeting was opened by Dr L. Verhoestraete, Director, Division of Health Protection and Promotion, who welcomed the participants. He said that this meeting of geneticists, epidemiologists and clinicians had been called to review the possible contribution of twin studies, a recognized tool in genetic research, to the broader field of epidemiological investigations, where so far they had found comparatively little use.

Professor D. D. Reid was elected Chairman; Professor L. Gedda, Vice-Chairman and Dr R. Cederlöf, Rapporteur.

Studies of general population characteristics include vital statistics such as mortality and morbidity data which are obtained on a routine basis. These data constitute one of the best sources of raw material for epidemiological studies and provide easily accessible information for basic research and for programme planning in control of disease. Very often they raise questions concerning the epidemiology of chronic disease, which may help delineate the relevant factors and provide guiding hypotheses for further research in this field. A deeper understanding of disease may also be arrived at through the study of individual characteristics in cross-sectional, retrospective and prospective studies, and through experimental investigations. A cross-sectional study can be used not only in determining prevalence of disease in a population, but it can also serve as the base-point for a longitudinal study of chronic diseases.

A girl carrying a de novo balanced 13-14 robertsonian translocation showed a clinical phenotype with severe hypotonia, hyperextensible joints, frontal bossing, asymmetric face, no mental retardation, severe scoliosis and motor delay. In situ hybridization analysis on chromosome spreads revealed the presence of the two centromeres in the rearranged chromosomes. Molecular analysis on genomic DNA showed the presence in the proposita of two chromosomes 14 of maternal origin and no chromosome 14 from the father indicating a maternal monocentric uniparental disomy for chromosome 14 (mUPD14). Our patient shows several similarities with other reported cases of mUPD14, suggesting imprinting of a region(s) of chromosome 14 and defining a possible mUPD14 Syndrome.

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

This paper is based on 45 cases in 27 families, all of which have been studied in Children Hospitals. In Switzerland almost all cases of infantile amaurotic idiocy (Tay-Sachs) have probably been collected, so that the stated 13 primary and 14 secondary cases may allow an estimation of the frequency of this character, which seems to oscillate temporarily. In the last 10 years no new cases have been observed.

All 24 autochthonus Swiss cases are from non-Jewish, mostly rural origin, in which Eastern Jews are not to be supposed as ascendants.

Our in all 27 families with TS make Slome's statistic of Jewish and non-Jewish cases in literature much more significant; the incidence of parental consanguinity is, as a matter of fact, nearly twice as high in families with non-Jewish origin.

There is no evidence of a milder and longer course of TS in non-Jewish families.

The mode of inheritance is, according to Slome, monohybrid autosomal recessive, though in remarkably many sibships there is an accumulation of cases. The reduction method, however, gives a percentage of 28,3 ± 6,2, coming quite near to the expectation of the Mendelian quarter.

The penetrance of the character is total, the expressivity generally very equal, with only a few deviations from the well—known clinical picture of TS.

The interfamiliar and intrafamiliar variability therefore is small. In not even one of the families studied have there been found other forms of lipoidosis, principally no cases of splenohepatomegalia Niemann-Pick. All available respective cases in Switzerland have been collected by the present author and will soon be published in these Acta. In none of these families with M. Niemann-Pick have cases of M. Tay-Sachs been seen. This fact is liable to prove that these clinically and anatomically very similar conditions derive from independent i. e. different mutations.

Modifying genes may account for the incidence of sibships in which all or almost all children died from M. TS.

Environmental influences do not seem to favour its manifestations.

If in the newer literature from the U.S.A. the Jewish cases of M. TS are still prevalent and if, as we heard, the concomitant manifestations occur fairly often in Israel, the origin may be sought in one at least 200 years old respective mutation in the Jewish population of a relatively restricted White-Russian era.

An analysis of all perinatal deaths occurring in twin pregnancies in Dundee women from 1956 to 1983 was performed. The uncorrected perinatal mortality rate fell from 116/1000 births in 1956-60 to 16/1000 births in 1981-83, this fall almost entirely taking place after 1975. Causes of death were identified using the Aberdeen Classification and a reduction in deaths in all cause groupings occurred. About half of the deaths were in the Premature, Cause Unknown group and a marked decrease in deaths in this group made the largest contribution to the improved perinatal mortality rate. This fall was partly due to a reduction in the incidence of extreme prematurity and low birth weight. Changes in obstetric management which may have influenced outcome included the introduction of routine early pregnancy ultrasound scanning, the use of tocolytic drugs, intrapartum fetal monitoring, epidural analgesia and an increase in Caesarean section rate from 2% in 1956-60 to 39% in 1981-83.

Suppose that L like-sexed and U unlike-sexed twins have been observed. Weinberg's method estimates the numbers of DZ andMZ twins as DZ = 2U and MZ = L—U. This method is based on the assumptions that (1) the sex ratio in DZ twins is 1/2 and (2) the sexes of DZ twins are determined independently and with the same probability in all parents; in consequence there should, on average, be equal numbers of like-sexed and unlike-sexed DZ twins. The first assumption is not exactly true, but the necessary correction is negligible. Departures from the second assumption would probably lead to an excess of like-sexed over unlike-sexed DZ twins; in consequence, Weinberg's method would underestimate the numbers of DZ twins and overestimate the numbers of MZ twins. The literature on the frequencies of like-sexed and unlike-sexed pairs among twins known to be DZ through other genetic markers is reviewed. It is concluded that there is no evidence of an excess of like-sexed twins among them, and that there is therefore no reason to doubt the validity of Weinberg's method. The extension of Weinberg's method to estimate the zygosity types of triplets and quadruplets is described; it is shown that the resulting estimates agree well with the results of direct zygosity determination by blood grouping.

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.

In conjunction with full-sib and parental observations, half-sib analysis permits an estimation of the genetic and environmental variance as well as a partitioning of the genetic variance into its additive, dominance and epistatic components. The offspring of identical twins are a unique class of human half-sibs who provide an unusual opportunity to resolve and measure several additional potentially important sources of human variation including maternal effects, the influences of common environmental factors and assortative mating.

The genetic model thus developed for the analysis of quantitative inheritance in man has been applied to the analysis of total ridge count and birth weight, confirming the existence of a major additive genetic effect on ridge count and a significant maternal effect on birth weight.

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

An increased incidence of twinning has been reported among patients with Klinefelter's syndrome (XXY) and their relatives, but no data have been reported about the incidence of XXY among twins. Results from our institution's antenatal testing clinic provide data about twins and XXY. In 1842 pregnancies tested, 21 were noted to be twin gestations. Five fetuses with XXY were detected in all pregnancies, of which there was a pair of MZ twins concordant for XXY and a pair of DZ twins discordant for XXY. The incidence of XXY in twins was thus 7,1%. The fetal phenotype of XXY was examined in aborted MZ twins and found to be mild. Notably, the testicular histology was normal. These cases confirm the previously reported association of twinning and XXY. The association of twinning and XXY implies a commonality of causation; however, a maternal age effect cannot be excluded. Our data suggest that there is an increased risk of XXY among twins.

Data on conjoined twins have been collected from 14 different malformation monitoring programs around the world. Among over 28 million births, 312 cases were identified. After considering underascertainment in one large program, the best estimate of the incidence based on the sum of induced abortions and births is 1.3 per 100,000 births. The distribution according to type of twinning, the sex distribution (39% males) and the stillbirth rate (47%) are presented. The presence of malformations not directly related to the area of fusion is discussed. In three women, thyroid disease was present and five women had been treated for infertility before conception.

The objective of this study was to evaluate the association between maternal factors, including rates of gestational weight gain before and after 24 weeks' gestation, and adequacy of intrauterine growth for gestational age at birth of triplets, as a mean Z-score of the triplet set. The study design was a retrospective, anonymous, pilot telephone survey of mothers of triplets and an historical cohort analysis of their prenatal weight gain records. The statistical analyses performed included multiple regression analysis to formulate a model for mean triplet Z-score (a measure of birthweight-for-gestational age) and analysis of variance to confirm and simplify the components of this model. Factors significant in the final model and their beta coefficients included weeks' gestation (-0.124, p <0.0001), rate of gain before 24 weeks' gestation (0.606, p = 0.005), and induced conception (−0.404, p = 0.01). Rate of gain > 1.5 lbs/week before 24 weeks was significant in the analysis of variance (p = 0.009). Better intrauterine growth for gestational age is achieved in triplet gestations with maternal weight gains of >1.5 lbs/week before 24 weeks' gestation.