The frequency of living twins born in Southern Moravia in the period 1960-1970 was studied and found to be 0.67%. No differences in twinning rate due to the years, seasons, districts or towns with 10,000 and more inhabitants in comparison with other localities, were found. An interesting hitherto undescribed phenomenon of twin-birth clustering in space and time was observed.

A simple additive model of genes plus environment, based on intrapair similarities observed in 35 MZ and 35 like-sexed DZ twin pairs, was used to estimate the relative contribution of genetically controlled phenotypic variance in psychomotor individuality. Subjects practiced 50 trials on a pursuit rotor apparatus under a 20-sec/20-sec, work-rest schedule with a 30 min rest pause allowed between trials 30 and 31. Analyses of the data disclosed that a greater proportion of genetic factors, as opposed to nongenetic factors, appears to account for existing individual differences in motor performance among individuals subject to similar environmental conditions. The strength of this genetic control, however, systematically diminished throughout the course of practice obeying a monotonie trend over trials.

We attempted to define parental anxiety in a population of parents of high-risk premature twins (mean birth weight 1.493 ± 227 kg; mean gestational age 33 ± 3.5 weeks), admitted to III level NICU. We specifically examined the following factors: gestational age of the twins, whether or not the twins had ventilatory support, pulmonary sequelae, major malformations or intra-ventricular hemorrhage, parental gender and highest level of education obtained by the parent. In the immediate pre-discharge period and a month later, a questionnaire (State-Trait Anxiety Inventory) was given to all parents of premature twins presenting for the discharge. The parents of 30 twins entered the study twice, at the discharge of their first twin (mean postnatal age 40 ± 32 days), and one month later. They included 15 mothers and 11 fathers, aged 33 ± 5.5 and 33 ± 4.2 years, and at the second evaluation 11 mothers and 10 fathers, respectively. As case-controls we examined parental anxiety of fifteen consecutive singleton high-risk prematures, with equal gestational age, discharged immediately after. Our results indicate that the parents of high-risk twin and singleton prematures present an elevated, lasting state-trait anxiety level. Pre- and post-discharge parental anxiety is more elevated (not significant) in twinning with respect to the prematurity alone. When assessed separately by parental gender, in both these groups an increased (not significant) anxiety was persistently found in the mothers. We recommend that, although neonatologists generally define the discharge of the high-risk premature based upon the acquired stabilization of vital parameters, they pay special attention to the twin group we have identified which is at increased risk for predischarge parental anxiety.

In peripheral blood cultures of a phenotypically abnormal Caucasian girl, a ring-shaped chromosome was observed in place of an E group member. The rest of the chromosomes of the complement did not show any obvious structural anomaly. The ring chromosome was noted in 100% of the recorded cells, and its size in individual metaphases remained fairly constant. It is suggested that this ring chromosome has become a permanent part of the complement of the patient.

This study is based on pedigrees of 192 patients with rheumatoid arthritis which are compared with pedigrees of 300 controls.

6,3 per cent of all relatives in the first group had rheumatoid arthritis compared to 0,38 per cent of all relatives in the control group. An hereditary predisposition to rheumatoid arthritis is definitevely to be admitted.

This predisposition is due to the presence of a principal autosomal dominant gene with reduced penetrance and variable expressivity. It seems to have no genetic relationship to the diathesis of allergic diseases and the diathesis of degenerative connective tissue disorders (mesenchymotic diathesis).

The increasing number of twin (and higher order) births is a matter of national concern for two reasons: First, the differential rates of preterm (< 37 weeks) delivery and low birthweight (< 2,500g) among twins compared to singletons; and second, the inordinate contribution of these infants to overall infant mortality, morbidity and long-term handicap. Data from all births in the U.S. during 1987 and 1988 was used to calculate distribution frequencies for gestational age at delivery, and birthweight, as well as mortality and handicap rates and the corresponding relative risks of these latter events for twins compared to singletons. A suggestion for improvement in the mortality and handicap rates and reduced costs among survivors is presented. This proposal is based upon data from the singleton and twin literature and the use of the prenatal invervention of adequate maternal nutrition during the pregnancy.

The purpose of this paper is to draw attention to the statistical implications of abortion risks being greater for twins than singletons, greater for MZ than DZ twins, and greater for one member of a twin pregnancy than both members. This last fact is important, because if one twin aborts the other is usually mistaken for a singleton at birth; thus allowing a given number of nonconcordant abortions to have a marginally greater effect on twin frequency than double the number of concordant abortions.

This feature of abortion hazards is shown in Tab. I, which is based on Sandon's calculations of concordance effects. The figures show how much greater is the effect of a high rate of nonconcordant abortions (Case B) than the effect of an equally high rate of 90% concordant abortions (Case A) or a lower rate of 60% concordant abortions (Case C). In other words, a low frequency of twins in general (and MZ twins in particular) should be typical of an abortion-ridden population and might be a means of recognizing diseases whose prevalence rates are misleading, because they are associated with an abortion hazard (i.e., inherited diseases and diseases acquired during embryogenesis).

The case is described of a child who presented a slight psychomotor retardation and malformative signs, together with an XYY caryotype, and who died at the age of 7 years from a medulloblastoma, as could be later confirmed by autoptic examination.

The relations between chromosomal and neoplastic pathology are described.

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

The population of Andhra Pradesh has been considered ideal for the study of inbreeding effects in view of its high incidence of consanguinity. Information for the present investigation was obtained from 1,091 consecutive hospital single births to study the genetic load in the newborn in terms of mortality and malformation as a consequence of inbreeding. The nature of consanguinity was examined and the frequency of uncle-niece marriages was found to be lower than in other parts of Andhra Pradesh. The mortality load in the newborn was found to be two lethal equivalents per individual, while the malformation load at birth was half the mortality load.

A total of 123 twin pregnancies were studied, 68 by records analysis only, and 55 by serial haematological assessment in detail. The incidence of low haemoglobin levels is found to be greater than in singleton pregnancy; evidence of iron and folic acid deficiency is common in sternal marrow aspirates but not in peripheral blood films. Routine haematinic prophylaxis in twin pregnancy is not advocated.

We present a new case of 11p15 duplication (trisomy 11p15) in a boy [46,XY,-21,+der(21), t(11;21)(p15.2;q22.3)] suffering from Beckwith-Wiedemann syndrome (BWS), whose phenotypically normal father carries a balanced translocation between chromosomes 11 and 21[46,XY, t(11;21)(p15.2;q22.3)]. The paternal grandmother has the same balanced translocation and is also clinically normal. BWS was suspected when the boy was 6 months old because of gigantism, macroglossia, visceromegaly, ear lobe creases and abdominal distention. Apart from the characteristic BWS phenotype, the boy has other features which are almost exclusively observed in 11p trisomy (high forehead with frontal upsweep of hair, wide central nose bridge, slightly beaked nose, chubby cheeks and severe mental retardation). So far, at least eight cases of 11p15 duplication have been described as patients with BWS. In six of these, the duplication was due to inheritance of a translocated or rearranged paternal chromosome. This was also the case in our patient. In the two other previously published cases, the 11p15 duplications were de novo, but in one of these, DNA analysis has subsequently shown that the duplication was of paternal origin. We discuss our observations in relation to the above-mentioned previous cases of 11p15 duplication and the possible role of genomic imprinting in the etiology of BWS.

A man of 32 is described suffering from a combination of three disorders: cutis verticis gyrata, severe mental deficiency and aplasia of the thyroid. Four of his close relatives were also severely retarded. The possibility is discussed of the syndrome being inherited through an X-linked recessive gene.

Measurements of height and weight have been undertaken on 201 pairs of twins and 46 sets of higher multiples once each at various ages through childhood. The heights of twins are comparable to the overall population of singletons, those of higher multiples are slightly undersized. However, the total group of twins were shorter than expected when compared with the heights of parents and siblings, but this was entirely accounted for by that component of the group who at birth had been very light for dates. The children in all groups of multiples were underweight for their height in comparison with standards of a comparable population and with their own siblings.

The degree of genetic determination of 4 digital and 16 palmar characteristics was investigated in an unselected series of 49 MZ and 51 DZ adult twins. Low indications of heritability were obtained for the qualitative traits, but 6 of the 8 h 2 estimates calculated for the quantitative measurements gave values above 0.70. In general, the results reported here are in agreement with those presented by other authors; however, the correlation coefficients observed for the A′d ridge count were lower than those of two other series. All palmar ridge counts seemed to be intercorrelated in a given individual; other expected relationships, however, were not observed. The fingerprints of MZ and DZ twins on the other hand, showed an unexplained difference.

Four hundred and thirty-four twins delivered from 220 women at Notre-Dame Hospital were studied during a period of 11 years (1969–1979). The maternal, fetal, and neonatal outcome was compared before and after 1974, the year ultrasonography and other changes in perinatal care were introduced in our institution. Early diagnosis occurred more frequently after 1974, together with increased antenatal hospitalization. Preeclampsia and hepatic cholestasis occurred in 19.5% and 9.5% of women, respectively. Preterm delivery occurred in 42.2% of the cases. The corrected fetal mortality rate was 30.2/1,000 and corrected perinatal mortality rate was 74.9/1,000. About 90% of the neonatal deaths occurred in infants born before 36 weeks. Internal version and complete extraction of the second twin increased the neonatal mortality sixfold compared to spontaneous delivery. Availability of ultrasound examination significantly reduced preterm delivery.

It is shown that the within twin-pair difference is the most important source of information in determination of twin zygosity using dermatoglyphic data. Inclusion of a measure of among-pair variability provides added discrimination beyond that found with the within-pair difference alone.

Physiological adaptation including expansion in plasma volume is exaggerated in women with twin pregnancies. In singleton pregnancy and multiparous twin pregnancies there is an association between plasma volume expansion and birth weight, but this is not so in primigravid twin pregnancies. Women with twin pregnancies have a similar dietary intake to singleton pregnancies, but it is not known whether there are differences with parity or zygosity. Absorption and utilisation of nutrients may be increased to meet demands for extra fetal growth. Nutrient supply and plasma volume expansion will be further discussed and their association with birth weight presented.

Dizygotic (DZ) World War II veteran twins who participated in the National Heart Lung and Blood Institute (NHLBI) Twin Study have been reported to have greater variance than monozygotic (MZ) twins for plasma high-density lipoprotein cholesterol (HDL-C), cholesterol in the low-density fraction of HDL (HDL2-C) and apolipoprotein A-I, a major protein component of HDL. It was hypothesized that a possible source of this difference in zygosity variance could be prenatal environmental influences related to placental type. Dermatoglyphics were used to provide a retrospective index of placental type in a subset of the NHLBI MZ twins aged 59-70. The MZ twins classified as dichorionic were found to have significantly greater within-pair variability than the monochorionic MZ twins for HDL-C, HDL2-C and Apo A-I. These findings indicate that intrauterine environmental influences on HDL are manifest later in life.

A statistical analysis has been carried out on the frequency of twin and triplet births in Poland in the years 1949-1971.

These frequencies appear to be higher than expected on the basis of Hellin's rule, there being 1 twin birth in 87 single births and 1 triplet birth in 118 twin births.

The share of MZ vs. DZ twins having been assessed through Weinberg's method, an analysis is carried out on maternal age, parity, and urban vs. rural environment. It is concluded that the frequency of polyovulation increases with parity, whereas it becomes reduced with age on account of menopause effect already at age 40.