It has been suggested that impairment of placental perfusion prior to delivery may manifest in early postnatal increase of creatinine values. We hypothesized that the smaller of a discordant set of twins would have a higher initial plasma creatinine value and decided to measure early plasma creatinine levels in discordant twins in order to evaluate whether this value may serve as an index of impaired placental perfusion. Plasma creatinine, urea nitrogen and blood hematocrit values were simultaneously measured in 35 sets of twins during the first day of life. The sets of twins were divided into 2 groups according to birth weight difference. Thus, 18 sets of discordant twins with birth weight difference greater than 15% comprised the GT group and 17 sets of twins with birth weight difference less than or equal to 15% comprised the LE group. The differences between the values obtained within each group were analyzed using the Wilcoxon Signed Rank test. In the GT group the mean plasma creatinine level of the smaller twins was significantly higher than the level of the larger ones (p = 0.03), but there was no statistically significant difference between values obtained in twins of the LE group. The mean plasma urea level was higher in the larger twins of both groups, however only the difference in the GT group was statistically significant (p = 0.01). The mean hematocrit of the smaller twins was higher in both groups, but only the difference in the LE group was statistically significant (p = 0.02). Generally, there was a negative correlation between gestational age and early creatinine values. These results apparently support the notion that prenatal exposure to impaired placental perfusion may compromise the creatinine clearance of the fetus and result in higher early creatinine values. Since the creatinine values in our growth-retarded twins were within the normal range, no distinguishing line for evidence of a uterine-placental compromise could be drawn. Whether a certain early plasma creatinine value is suggestive or indicative of an intra-uterine hypoxic-ischemic insult, should be determined by documented instances of severe fetal compromise prior to delivery.

Within a period of 6 years (1994–99) we registered 29 triplet deliveries out of a total of 13,969 hospital deliveries (0.02%). Since there is limited information about specific problems of chorionicity in triplet pregnancies, we analysed the 29 cases according to origin of pregnancy and chorionicity. We here report on two cases with a high risk according to chorionicity with dichorionic (DC) diamniotic (DA) triplet pregnancies. Out of the two cases, one pregnancy was spontaneous and one originated after in-vitro fertilization. In both pregnancies, cord entanglement was detected early in pregnancy (at 10 and 15 weeks) by color Doppler velocimetry demonstrating different heart rates within the segment of the entangled umbilical branches. The pregnancies were followed by documenting fetal behavior and color Doppler velocimetry of umbilical and fetal arteries at weekly intervals. In both cases, a primary Cesarean section was performed after detection of lung maturity. In the first case, one of the MA triplets had a transposition of the great arteries and abnormal lung vein drainage, which was the reason for neonatal death three weeks postnatally. Although early cord entanglement has been described in MA twins, this series demonstrates that it can as well be demonstrated in MA triplets. The early detection allows for extensive surveillance of the a priori high risk triplet pregnancy.

To evaluate the accuracy of ultrasound in early detection of chorionicity and amnionicity in twin pregnancies and evaluate the role of operator-experience, a prospective follow up of 87 consecutive twin pregnancies was performed. Chorionicity and amnionicity were determined by 17 different observers, divided in 2 groups on the basis of their experience, using a composite of US markers at the first US examination confirming a viable intrauterine twin pregnancy. Accuracy of prediction was determined for both groups by comparison with postnatal pathology. From the 87 pregnancies examined at 10.1 (minimum 5.5 weeks, maximum 26.0) weeks of gestation, pathology was available in 82 cases and a correct prediction of chorionicity was made in all but two cases, both being diagnosed as monochorionic while dichorionic by observers belonging the more experienced group. No monochorionic pregnancy was missed and amnionicity was correctly diagnosed in all cases, including two monoamniotic twins. We conclude that use of a composite of ultrasound markers for early detection of chorionicity and amnionicity is reliable in a clinical setting where physicians with a variable degree of experience perform ultrasound examination.

The aim of this research was to study fetal and infant mortality in Sweden between 1973 and 1996 in twins vs singletons in relation to gestational duration. Analysis was of fetal and infant mortality based on the number of pregnancies at risk as the denominator rather than the number of deliveries each week. The analysis was based on information stored at the Medical Birth Registry (MBR), the National Board of Health and Welfare, Stockholm. The MBR keeps records on virtually all pregnancies (> 99%) regarding delivery and neonatal information, and for infant mortality up to 1 year of age. During the study period, 2,206,738 singleton and 52,658 twin births were registered. Risk evaluation was made as odds ratio (OR) with a 95% confidence interval. The material was stratified according to parity, maternal age, year of delivery, and delivery unit. Results showed the OR for twin births before 34 weeks gestation was 6 to 8-fold increased compared with singletons. The OR for fetal mortality was increased in all gestational weeks, and like-sexed twins had a consistently poorer prognosis compared to unlike-sexed. Between 1989–96, unlike-sexed twins had a fetal mortality approaching that of singletons. In conclusion, real progress in reduction of infant mortality in twins may be impossible until the high incidence of preterm births can be decreased. Hypothetically, about 100 twin labors would have to be induced to avoid one fetal death in like-sexed twin pregnancies.

Data for sets of multiples under 16 years of age were obtained from the population censuses of Japan in 1990 and 1995. These numbered 147,188 twin pairs, 1410 sets of triplets, 59 sets of quadruplets, and 3 sets of quintuplets in 1990, with the corresponding numbers in 1995 being 141,354, 2,211, 136 and 12, respectively. The total number of sets of multiples was 148,660 in 1990 and 143,713 in 1995. Twinning, triplet, quadruplet and quintuplet rates were estimated for each age. Rates of monozygotic twins and triplets remained constant age by age up to 15 years, while the dizygotic twinning rate, and rates of di- and tri-zygotic triplets decreased over the same period. Quadruplet and quintuplet rates also decreased. The accuracy of estimating number of multiples from census data is discussed using data on vital statistics.

The incidence of twin births in Accra and Kumasi, the two major cities in Ghana, was investigated. In Accra, data were collected from the Korle-Bu Teaching Hospital while data were collected and analyzed from the Komfo Anokye Teaching Hospital in Kumasi. Both hospitals are the leading teaching hospitals in Ghana. The data consisted mainly of single and twin births recorded in the hospitals over a period of 12 years in Accra (1988–1999) and 15 years in Kumasi (1985–1999). The study revealed an incidence of 33.4 twin births per thousand live births for Accra and 26.6 twin births per thousand live births for Kumasi. Though these values are not as high as those reported among the Yoruba tribe of southwest Nigeria, who are reported to have the highest twin birth rates in the world, the present values still rank among the highest recorded twin birth rates.

We have established a large cohort of twins to facilitate studies of the role of genetics and environment in the development of disease. The cohort has been derived from all multiple births occurring in California between 1908–82 (256,616 in total). We report here on our efforts to contact these twins and their completion of a detailed 16 page risk factor questionnaire. Addresses of the individuals were obtained by linking the birth records with the California Department of Motor Vehicles (DMV) roster of licensees. To date this has been completed for twins born between 1908 and 1972 (200,589 individuals). The linkage has revealed 112,468 matches and, because of less complete DMV records in some years, was less successful in older females than in younger females and all males. Over 41,000 twins have participated by completing the questionnaire. Based on estimates of numbers of individuals receiving a questionnaire, we estimate our crude response rate to be between 42.2% and 49.6%, highest among females in their 40s (62.8%). We describe the representativeness of the twins in the original birth cohort, those identified by the linkage, and those completing the questionnaire. Compared to the 1990 resident population of California-born resident singletons, the respondents were of similar age, sex, race and residential distribution (for although we were able to locate fewer older females, they had a higher response rate), but were less likely to have been educated for more than 12 years. We provide a brief synopsis of studies nested within this cohort. We also elucidate our plans for expanding the cohort in the near future.

We have used Swedish monozygotic twins concordant for breast cancer to study genetic changes associated with the development of breast cancer. Because loss of heterozygosity (LOH) at a specific genomic region may reflect the presence of a tumour suppressor gene, loss of the same allele in both of the twins concordant for breast cancer may pinpoint a tumour suppressor gene that confers a strong predisposition to breast cancer. DNA samples extracted from the matched tumour and normal tissues of nine twin pairs were analysed for allelic imbalance using a set of microsatellite markers on chromosomes 1, 13, 16 and 17, containing loci with known tumour suppressor genes. The two main regions, where more twin pairs than expected had lost the same allele, were located at 16qtel, including markers D16S393, D16S305 and D16S413, and at 17p13, distal to the p53 locus. Our results show that the monozygotic twin model can be used to suggest candidate regions of potential tumour suppressor genes, even with a limited number of twin pairs.

The objective was to investigate the genetic epidemiology of figural stimuli. Standard figural stimuli were available from 5,325 complete twin pairs: 1,751 (32.9%) were monozygotic females, 1,068 (20.1%) were dizygotic females, 752 (14.1%) were monozygotic males, 495 (9.3%) were dizygotic males, and 1,259 (23.6%) were dizygotic male-female pairs. Univariate twin analyses were used to examine the influences on the individual variation in current body size and ideal body size. These data were analysed separately for men and women in each of five age groups. A factorial analysis of variance, with polychoric correlations between twin pairs as the dependent variable, and age, sex, zygosity, and the three interaction terms (age x sex, age x zygosity, sex x zygosity) as independent variables, was used to examine trends across the whole data set. Results showed genetic influences had the largest impact on the individual variation in current body size measures, whereas non-shared environmental influences were associated with the majority of individual variation in ideal body size. There was a significant main effect of zygosity (heritability) in predicting polychoric correlations for current body size and body dissatisfaction. There was a significant main effect of gender and zygosity in predicting ideal body size, with a gender x zygosity interaction. In common with BMI, heritability is important in influencing the estimation of current body size. Selection of desired body size for both men and women is more strongly influenced by environmental factors.

Data of the Danish Twin Registry on monozygotic and dizygotic twins are used to analyse genetic and environmental influences on susceptibility to heart diseases for males and females, respectively. The sample includes 7955 like-sexed twin pairs born between 1870 and 1930. Follow-up was from 1 January 1943 to 31 December 1993 which results in truncation (twin pairs were included in the study if both individuals were still alive at the beginning of the follow-up) and censoring (nearly 40% of the study population was still alive at the end of the follow-up). We use the correlated gamma-frailty model for the genetic analysis of frailty to account for this censoring and truncation. During the follow-up 9370 deaths occurred, 3393 deaths were due to heart diseases in general, including 2476 deaths due to coronary heart disease (CHD). Proportions of variance of frailty attributable to genetic and environmental factors were analyzed using the structural equation model approach. Different standard biometric models are fitted to the data to evaluate the magnitude and nature of genetic and environmental factors on mortality. Using the best fitting model heritability of frailty (liability to death) was found to be 0.55 (0.07) and 0.53 (0.11) with respect to heart diseases and CHD, respectively, for males and 0.52 (0.10) and 0.58 (0.14) for females in a parametric analysis. A semi-parametric analysis shows very similar results. These analyses may indicate the existence of a strong genetic influence on individual frailty associated with mortality caused by heart diseases and CHD in both, males and females. The nature of genetic influences on frailty with respect to heart diseases and CHD is probably additive. No evidence for dominance and shared environment was found.