The increasing rates of preterm birth among twins implicate that solid data on associated risks and outcomes are required. Assessment of zygosity is often based on clinical criteria (evaluation of placenta; same gender, birth weight discordance as surrogate criteria for monochorionic/monozygotic twins). The aim of this study was to compare clinical versus genetic assessment of zygosity and to c...

The predicted incidence of liveborn monozygotic trisomy 18 twins is one per million births. The first case of liveborn monozygotic trisomy 18 twins was reported in 1989 and we report a second case in which striking phenotypic discordance existed. The probability of monozygotic trisomy 18 twinning and the mechanisms for phenotypic discordance in trisomic twins is discussed.

It has long been common knowledge that certain twins resemble one another in a remarkable way. The fact that many more like sexed twins are born than the theoretical ratio 1: 2: 1 would demand constitutes evidence in favour of the belief that such twins are monozygotic, for the actual figures of twin births can be adequately explained on the assumption that about one half the pairs of like sexe...

Epigastric heteropagus refers to unequal and asymmetric conjoined twins in which the dependent component (parasite) is smaller and usually attached to the epigastrium of the dominant component (autosite). Epigastric heteropagus is a very rare type of conjoined twins. It is generally assumed that conjoined twins represent a form of monozygotic twinning, but there has been no confirmation of this...

64/105 subjects who have a twin with multiple sclerosis included in a study of clinical concordance also underwent MRI of the brain. 8/23 monozygotic and 1/41 dizygotic co-twins from this subgroup were clinically concordant of whom 8/9 had MRI appearances typical of multiple sclerosis. Of the 48 clinically discordant twins aged less than 60, abnormalities on MRI were detected in 6/15 (40%) mono...

OBJECTIVE The purpose of this study was to evaluate chorionicity and zygosity as risk factors for adverse perinatal outcomes in twins. STUDY DESIGN A population-based, retrospective cohort study was conducted of all twin deliveries in Nova Scotia, Canada, from 1988 to 1997. Chorionicity was established by histologic examination. Zygosity was determined by chorionicity, sex, and infant blood g...

Epidemiological studies have consistently shown a positive association between size at birth (i.e. birth weight or birth length) and height in children, adolescents and adults. To examine whether this association is explained by genetic or nongenetic (intra-uterine) factors, we investigated birth weight, birth length and height in 60 dizygotic and 68 monozygotic adolescent twin pairs still livi...

A case of concordant oligodendroglioma in monozygotic twins is reported. The twins were also concordant for uterine leiomyoma and one twin partner had fibroadenoma and lipoma of the breast and myelofibrosis. As very few cases of concordant glioma in monozygotic twins have been published and no such cases in dizygotic twins, a genetic influence in the aetiology of glioma can only be suggested.

Since 1979, a continuing study of monozygotic and dizygotic twins, separated in infancy and reared apart, has subjected more than 100 sets of reared-apart twins or triplets to a week of intensive psychological and physiological assessment. Like the prior, smaller studies of monozygotic twins reared apart, about 70% of the variance in IQ was found to be associated with genetic variation. On mult...