The twinning, triplet and quadruplet rates were found to be 23.8, 0.3 and 0.04 per thousand maternities, respectively in a survey of 71,773 maternities carried out in Ibadan and Igbo Ora, Nigeria. This represents a dramatic fall from the rates found in previous studies. The findings are discussed in the light of changing dietary habits.

The objective of this study was to answer the question whether there is the relation between the uterine capacity, estimated by the total birth weight of fetuses, and the duration of twin gestation. The material for researches contains data received from the books of births and case records concerning the pregnant who gave births to twins in the Institute of Obstetrics and Gynecology of the Medical University in Lódź between 1970-1998. The final analysis concerned only gestations lasting more than 29 weeks, without any complications (excluding prematurity and the growth-discordant twins), and when gestational age was exactly known. The selected group was finally composed of 188 pairs of twins. The analyses considered relations between total birth weight of twins, the sex of newborn babies, parity, and the duration of gestation. The duration of the analyzed twin pregnancies was 35,6 weeks, including primiparous with 35,8 weeks, and multiparous – 35,1 weeks. In the group of male-male twin pairs the average duration of pregnancy was 35,7 weeks, in unlike-sexed pairs – 35,6 weeks, and in female-female pairs – 35,5. In the group of the primiparous having male-male twin pairs the average duration of pregnancy was 35,1 weeks, unlike-sexed pairs – 36,4 weeks and female female pairs – 36,6 weeks, while in the group of multiparous relatively: 36,4, 35,4, 35,0 weeks. The total birth weight of the specific pairs of twins was from 2270 g to 6900g (average 4794g), while in 92% <5500g. In the primiparous group it was 4908,1 g. and in the multiparous group – 4663,1 g. Analyzing the total twins' weight according to the fetal gender and parity it was found that in primiparous with male-male twins - 4715,3, unlike-sexed – 5271,6 and female-female – 4967,5, whereas in multiparous relatively: 4961,5, 4692,6, 4414,0. The shortening of twin pregnancies was caused by the following factors: total body mass achieved by fetuses was > 5500 g, presence of male sex in twin pregnancies (only in primiparous), and also the multiparity.

Ultrasonic assessment of fetal weight derived from multiple measurements of the fetus has become accepted in clinical practice as being useful in singleton pregnancies. Several different formulae for estimating fetal weight have been derived from differing measurements of the fetus, such as biparietal diameter, trunk circumference, and femur length. To date, there has been no attempt to evaluate such a technique in multiple pregnancy. This study aims to see whether the formulae derived for singleton pregnancy are applicable to twin pregnancies. Estimated fetal weight will be derived by mathematical modelling from ultrasonic measurements made within a week of delivery and the results compared with the actual birthweight to give an indication of how good such estimated fetal weights are. Factors to be considered in the analysis include whether there are differences between Twin I and Twin II, differences of presentation with twins and differences by gestation at delivery.

During the years 1979-1980, a prospective study was carried out to evaluate the value and efficacy of routine hospital bed rest in the prevention of premature birth and pregnancy complications in twin gestation. This was done by comparing hospital bed rest to special antenatal care at outpatient clinic. Since the results did not support the idea of using routine hospital bed rest, this was abandoned. Because the material was rather small, the results of the changed policy of management were controlled in the present follow-up study. The material consists of 102 twin pregnancies diagnosed during the years 1982-1983. The number of deliveries before the 34th gestational week and of < 1500 g weighing infants were still decreasing (9.0% and 3.0%). Perinatal mortality after the 24th gestational week was 2.0%. The follow-up study confirmed the unefficacy of routine hospital bed rest. Early diagnosis is the basis of the management of twin pregnancy. This allows counselling of the pregnant women, regular examinations to detect pregnancy complications, and also planning of the delivery.

To study genetic contribution to complex body size traits, the intrafamilial correlation and regression analyses along with twin study method have been used. The data are based on a sample of 45 MZ and 101 DZ twin pairs, their 125 singleton siblings, 104 fathers and 103 mothers in 146 Punjabi families living in Chandigarh, India. Twin study gives no evidence of inequality of means and variances between zygosities. Within-pair genetic variance ratios, correlations, regressions of offspring on midparent and single parent are all significant at 0.1%, thus indicating strong genetic component. Heritability estimates are higher for longitudinal body traits than the breadth dimensions. The resemblance of the children with the parents of either sex is not equal. Higher maternal influence is indicated for a number of body traits. The results on familial correlations do not support the hypothesis of sex-linked inheritance for any of the traits considered in this investigation. These results have been compared with those from other such studies.

Previous twin studies provide evidence for genetic contributions to individual differences in reading achievement, but the nature of those genetic effects is uncertain. Reading is a complex behavior composed of many lower-level skills including attention, memory, learning ability, and the integration of auditory and visual information; genetic influences may exert their effects through these lower-level skills. This study evaluated the relationship between auditory-visual integration (AVI) and reading achievement and assessed genetic variance in AVI and reading achievement using the conventional twin model (comparison of identical twins with fraternal twins).

The final sample consisted of 109 first- and second-grade volunteer twin pairs. Of the 89 same-sexed pairs, 57 pairs were classified as monozygotic, 31 pairs as dizygotic, and one remained unclassified; zygosity determination included examination of the intrapair similarity of genetic markers, dermatoglyphics, and/or physical appearance. The childrens' test battery included reading achievement tests (Woodcock Reading Mastery Tests) and the AVI task as well as estimates of general intellectual ability (Vocabulary and Block Design tests from the Wechsler Intelligence Scale for Children-Revised), auditory memory (Auditory Sequential Memory subtest of the Illinois Test of Psycholinguistic Abilities), comparison of auditory patterns, and comparison of visual-spatial patterns. Although the presence of heritable variation in reading achievement has been reported previously [22, 23, 30, 34, 50, 57], it does not account for all of the reliable variance; accordingly, two family questionnaires (Attitudes Toward Education and Moos' Family Environment Scale) and one dealing with first-grade method(s) of reading instruction were included to assess possible environmental factors.

The most unique aspects of this study were the young age of the children studied and the twin analyses of the auditory-visual integration test battery. Evidence for heritable variation in reading achievement was found in this young sample consistent with the results of studies using older children. The main thrust of this project was to investigate possible “lower-level” sources of this heritable variation, particularly auditory-visual integration. As a first step, it was necessary to establish the presence of a significant relationship between reading achievement and auditory-visual integration, independent of general intellectual ability. The partial correlations between the reading achievement measures and AVI (WISC-R test scores partialled out) ranged from 0.10 to 0.49 and were generally significant. Factor analysis of the children's test battery supported the idea that the integration aspect of the AVI task (auditory-visual and/or spatial-temporal) was the aspect of this skill related to reading achievement rather than auditory memory or visual-spatial ability, which also contribute to success on the AVI task. Twin analyses of the AVI task revealed evidence of the presence of heritable variation. However, the task relates to other skills exhibiting genetic variance, and it could not be determined whether aspects of the AVI task independently related to reading achievement were the sources of the heritable variation observed.

Although this study emphasized genetic relationships, environmental contributions to variation in reading achievement were also considered in a preliminary fashion. Family environmental data suggested that exposure to and emphasis on intellectual and cultural activities promote reading achievement.

In conclusion, a positive and significant relationship between reading achievement and auditory-visual integration, independent of general intellectual ability, was established for a first- and second-grade sample. One environmental variable, intellectual-cultural orientation of the family, was also related to reading achievement. Evidence indicative of the presence of genetic variance was presented for reading achievement, as previously reported in older twin samples, and for auditory-visual integration.

Red cell acid phosphatase phenotypes were determined in 517 unrelated persons from Sweden (317 men, 200 women). The observed gene frequencies were pA = 0.372; pB = 0.558; pC = 0.070.

Experiences in 101 cases of disputed paternity with 167 men involved are reported. On grounds of red cell acid phosphatase phenotypes, ig men (in 18 cases) could be excluded.

In all 112 mother-child combinations studied the distributions of phenotypes were in agreement with the genetical hypothesis suggested by Hopkinson et al (1963).

In order to test the possible effect of maternal inbreeding upon non-disjunction, ancestors of 104 children with Down's syndrome born to younger mothers were identified on the basis of official records. Among them, 6 had related parents, while 10 of the fathers and 12 of the mothers had also such parents. The relationship comprises first-cousins, first-cousins once removed, and second cousins. It was concluded that recessive genes are unlikely to be involved in the aetiology of non-disjunction of the 21st autosome, at least in younger mothers.

A school population has been screened to locate same-sexed twins with myopia and also to compare intelligence test performance of myopic and nonmyopic individuals. Augmentation of the twin data by a survey of the world literature has led to the identification of a total of 106 MZ twin pairs, 100 of them concordant for myopia, as well as 41 DZ pairs, 12 concordant. Myopic students score eight points higher on IQ tests than nonmyopes, the entire bell shaped distribution curve being shifted to a higher range. The intellectual gain precedes in time the development of nearsightedness.

The Authors report on a pair of MZ twins, only one of which affected by the Duchenne-type myopathy. Monozygosity is supported by the success of a reciprocal skin-graft.

Various hypotheses are discussed, including that of a somatic mutation during the first division of the egge producing the twins.

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.

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.

Twin reversed arterial perfusion (TRAP) syndrome is a rare but severe complication of monozygotic monochorionic twin pregnancies. The outcome is invariably fatal for the abnormal twins and for 50-75% of the normal co-twins. The prenatal diagnosis of the TRAP always has to be presumed in a multiple pregnancy within which a twin pair grows whenever cardiac activity can not be proved echographically. We present discuss – based upon literature research – pathogenic mechanisms, pathologic-anatomic, echographic diagnosis and management of these high-risk pregnancies.

In order to estimate genetic variance and heritability of systolic blood pressure (SBP), diastolic blood pressure (DBP), serum cholesterol and triglyceride levels, a total of 235 (79 male and 82 female MZ, 41 male and 33 female DZ) twin pairs, recruited from 12 junior high schools in Taipei city, were studied. Statistically significant genetic variance observed for SBP, DBP, serum cholesterol and triglycerides persisted after adjustment for age and anthropometric characteristics. However, further adjustment for dietary preference, beverage consumption, and other host and environmental factors gave different results: genetic variance of adjusted SBP and DBP was still significant, while significance was found only in males for cholesterol and in neither males nor females for triglycerides. Heritability estimates of unadjusted SBP, DBP, cholesterol and triglycerides were 0.27, 0.45, 0.21 and 0.41, respectively, for males, and 0.15, 0.42, 0.41 and 0.82, respectively, for females. After adjustment for age, anthropometric characteristics, host and environmental factors, the heritability estimates of SBP, DBP and cholesterol were 0.64, 0.72 and 0.50, respectively, for males, and 0.40, 0.60 and 0.37, respectively, for females.

The statistics of twin births in Australia and Italy were examined and the frequencies within the two countries at different periods of time compared. There has been an increase in monovular twin frequencies in Australia over a period of 25 years in spite of an increasingly higher proportion of first maternities amongst total maternities and generally lower maternal age. The cause of the increase could not be ascertained because of insufficient information. The decrease in gross frequency which occurred in Italy was found to derive from the smaller number of maternities to women of high parity in recent years. The frequency of twin births to women of corresponding age and parity remained unaltered and differed only slightly from comparable groups of Australian women.

The application of an ammoniacal silver procedure to the staining of human metaphase chromosomes is described. A map based on the differential staining characteristics of chromosome segments is presented.

A study of fingers characteristics was made on 1387 school children.

1. Clinodactyly (5th finger) with an angle of inclination of 21.3 ±0.7 degrees, was found in 15.2% of the male and 8.06% of the female white children between the ages of 5 and 12. These represent the heterozygotes of the population, Cc, while the extreme form of clinodactyly, with an angle of inclination of over 30 degrees, most likely represents the homozygotes of the population, CC.

2. Curved index finger (2nd) occurs less frequently than clinodactyly (in 2.22% of the group studied).

3. Flexed little finger (5th) occurs least often, about 1 in 320.

4. Bilateral penetrance ratio has been defined. Clinodactyly has a bilateral penetrance ratio of 0.77 in males and 0.64 in females. The curved index finger has a bilateral penetrance ratio of approximately 0.75.

5. Clinodactyly also occurs in Negro children.

6. An instrument is described for measuring the angle of inclination of clinodacyly.

Changes in the management of 1120 twin pregnancies delivered in Tampere University Central Hospital during the years 1964-1985 were studied, together with changes in the pattern of perinatal deaths. Perinatal mortality decreased from 7.4% in 1964-68 to 3.5% in 1981-85. There were no significant changes in stillbirths. The decrease of perinatal mortality resulted from a reduction in early neonatal deaths, mainly those due to respiratory distress syndrome. Changes in obstetric management include earlier diagnosis by ultrasound, intrapartum monitoring, and an increase in cesarean section rate from 4% to 32%. There is still a need for a reduction in the number of very early preterm births, and for more effective intrauterine supervision of twin pregnancies.

The Aiome dwarf tribe in the mountains near the Ramu river and its southern tributaries was studied. Observations, measurements and photographs were made of 15 men and five women who came in a party to the Aiome airstrip. The measurements are embodied in Table 1 (p. 280). They include eye and skin colour; head length and breadth; ear length and breadth and the presence of a lobe; stature; development of brow ridges and relative depression of the nasal root. Other observations are in the text. The mean male stature was 147.9 cm which is roughly the same as that of the Congo Pygmies. The shortest woman was only 125.5 cm. high. The C.I. of the men was 78.51 and the ears are smaller than in most races.

The head-dress, decorations and “dances” are illustrated in Figs. 1-18.

The skin colour of Papuans is a shade lighter than in the Australian aborigines. In a study of skin colour of Papuans, Macintosh (1960) finds that the natives recognize and have names for three shades of colour. These appear to be due to (1) the homozygous (2) the heterozygous condition, and (3) the absence, of a minor gene for skin colour.

The fact that the blood group genes A, B, M, S, R1 and R2 of the Aiome dwarfs are closely similar to those of the tails in the Mount Hagen area justifies the conclusion that a single gene dwarf mutation is involved. The Aiome and Wissel Lake dwarfs (400 miles apart) differ greatly in the frequency of the A, M, S and R2 (cDE) genes, but agree in the B and R1 (CDe) frequencies. The blood groups of the Congo Pygmies similarly agree with those of the Bantu, from whose ancestors they may have been derived.

The early literature regarding dwarf races is reviewed and the question of a Negrito race in southeast Asia is discussed. It is concluded that the term Negrito should probably be confined to the dwarf race in the Philippines. They perhaps reached the Philippines from Borneo when the sea-level was down during the last ice age.

On the basis particularly of skull form, the Andamanese were probably derived from the tall population of adjacent Malaya or Burma. The significance of their steatopygy and peppercorn hair is not clear, as these characters are found in the South African Bushmen.

The Semang of Malaya are mixed and of doubtful origin. The dwarf nature and relationships of the Kadar in South India remains uncertain. The incised designs on their wooden combs suggests a possible very ancient cultural connection with the Malayan dwarfs and the Philippine Negritos. A Negrito-like remnant in Queensland may represent in part the source from which the Tasmanian aborigines developed. The Veddas are outside the Negrito grouping. They are probably Australoids of reduced dimensions who migrated to Ceylon during the last ice age.

The various dwarf groups in New Guinea are of local (and probably relatively recent) origin, having no connection with Negritos, who appear to be of much earlier origin, probably before the last ice age. Various localities with populations of different mean stature are listed in Table 3, and others are mentioned in the text.

A statistical treatment of Bijlmer's measurements of stature, nasal and cephalic index, with the aid of Dr. Fraser Roberts, shows that many of the groups in Dutch New Guinea are significantly different. A fuller statistical investigation dealing with both stature and blood groups, is required to elucidate this situation. A tentative hypothesis is put forward, involving the fractionation of the original dwarf gene in the process of back-crossing between tails and dwarfs.

In New Guinea the coastal people are the tallest, those in the higher mountain areas are conspicous dwarfs, populations in intermediate areas being shorter in different degrees than the coastal tribes. That crossing takes place is shown by the occurrence of occasional men who are much taller than the rest of their group or tribe. Further studies of Papuan statures should also throw light on the origin of multiple genes for stature.

Prior studies have suggested that the risk of testicular cancer among dizygotic twins may exceed that among monozygotic twins or the general population. Cryptorchidism is associated with testicular cancer and twinship, and therefore might potentially explain the findings of the prior studies. In 1993-1994, when they were 66 to 77 years of age, 14,326 twin individuals in the National Academy of Sciencies-National Research Council Twin Registry were interviewed by telephone. A history of testicular cancer was reported by 5 (0.08%) of 5951 monozygotic twins and 11 (0.16%) of 6992 dizygotic twins. Follow-up interviews concerning testicular cancer risk factors and treatment were able to be administered to 4 of the monozygotic and 9 of the dizygotic twins reporting testicular cancer. A history of cryptorchidism was reported in the follow-up interview by only one dizygotic twin. Our data agree with the results of prior studies reporting a more frequent occurrence of testicular cancer among dizygotic than monozygotic twins. Although somewhat limited by small numbers, our study also suggests that the findings of increased testicular cancer in dizygotic twins are not explained simply by increased occurrence of cryptorchidism in twins.