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Multiple births after artificial induction of ovulation (AIO) are usually considered to be due to fertilisation of multiple ova. In the East Flanders Prospective Twin Study between 1978 and 1985 the frequency of zygotic splitting after AIO (1.2%) was significantly higher than the expected frequency (0.45%) among spontaneous twins and triplets. Moreover,(More)
The inheritance of spontaneous dizygotic (DZ) twinning was investigated in 1,422 three-generation pedigrees ascertained through mothers of spontaneous DZ proband twins. DZ twinning was modelled as a trait expressed only in women. The penetrance was modelled first as a parity independent and secondly as parity dependent. The observed frequencies of maternal(More)
OBJECTIVE The aim of this study was to present customized twin-specific birth weight standards. The relative contribution of gestational age, maternal factors, twin factors and placental factors to the birth weight was evaluated in a multivariate approach. SUBJECTS AND METHODS Perinatal data were obtained from 10,177 live-born twins from the East Flanders(More)
OBJECTIVE To assess the relation of umbilical cord insertion and fusion of placentas with birthweight in monozygotic monochorionic, monozygotic dichorionic, and dizygotic twins. DESIGN A prospective population study. POPULATION 4529 liveborn twin pairs whose birthweight was recorded, placentas were examined, and site of umbilical cord insertion was(More)
Two novel approaches to the analysis of twin data are illustrated with data from birth weight in twins. First, two possible covariates of birth weight are fitted to the data simultaneously, allowing for linear effects of these variables, and their correlation. Second, information on chorionicity is used to estimate the effects of chorion type on birth(More)
This study focuses on the quantification of genetic and environmental sources of variation in physical fitness components in 105 10-yr-old twin pairs and their parents. Nine motor tests and six skinfold measures were administered. Motor tests can be divided into those that are performance-related: static strength, explosive strength, running speed, speed of(More)
The East Flanders Prospective Twin Survey (EFPTS) is a registry of multiple births in the province of East-Flanders, Belgium. It has several unique features: it is population-based and prospective, with the possibility of long-term follow-up; the twins (and higher order multiple births) are ascertained at birth; basic perinatal data are recorded; chorion(More)
Congenital malformations have been investigated in a consecutive series of 445 monozygotic twin pairs coming from two twin surveys numbering 1,424 pairs. Concordant malformations were found in 6 pairs, discordant in 20 pairs. The significance of these findings is briefly discussed. The methodology of the prospective twin studies is described. The diagnosis(More)
OBJECTIVE To evaluate the specific contribution of artificial induction of ovulation to the increasing number of multiple gestations in East Flanders and the effects of this treatment on the frequencies of monozygotic and dizygotic twinning. DESIGN Since 1976 the East Flanders Prospective Twin Study has collected data on artificial induction of ovulation(More)
This study investigates the basic assumption of homogeneity of monozygotic (MZ) twins: are there differences according to the timing of the zygotic splitting, early in dichorionic (DC) and later in monochorionic (MC) pairs? We assessed the IQ of 451 same-sexed twin pairs of known zygosity and chorion type with the Wechsler Intelligence Scale for(More)