Relationship between zygosity and chorionicity

The frequency and clinical significance of twin gestations according to zygosity and chorionicity.

relationship between zygosity and chorionicity

PDF | Accurate determination of zygosity and chorionicity is essential in all multiple maternities. The parents and Address: Association for Scientific Research in Multiple Births, between monozygotic (MZ) and polyzygotic (PZ) twins,. triplets. zygosity, chorionicity, triplets, microsatellites, assisted reproduction technologies When the division occurs between Days 8 and 13 post-fecundation, the . All placentas were immediately identified in relation to their triplets. This is most accurately determined between weeks 6 and 9 of gestation, and to determination of chorionicity in twins without early ultrasounds information.

We conclude that the influence on the MZ twin correlation of the intra-uterine prenatal environment, as measured by sharing a chorion type, is small and limited to a few phenotypes.

Difference between monozygotic and dizygotic twin

This implies that the assumption of equal prenatal environment of mono- and DC MZ twins, which characterizes the classical twin design, is largely tenable.

Electronic supplementary material The online version of this article doi: Chorion, Record linkage, Equal environment, Prenatal, Twins, Heritability estimate Introduction The classical twin design has been the most productive method to assess heritability in the analysis of complex human traits. Its widespread application has established the importance of genetic effects on a very large number of complex traits in many populations.

Notwithstanding its utility, this design is based on several assumptions, and this has raised valid questions concerning the results that it has produced. One source of possible bias in twin-based heritability estimates is chorion sharing, i.

The frequency and clinical significance of twin gestations according to zygosity and chorionicity.

MCMZs share a single placenta, and so all blood-borne factors, emanating from the mother or the placenta.

Monochorionicity may be associated with vascular anastomosis twin-to-twin blood transfusionwhich is disadvantageous to both twins. MCMZ twins can either share one amnion, or each have their own amnion [i. DCMZs are thought to arise earlier during the morula stage, and, like DZ twins, have individual placentas. Any bias in twin based heritability estimates attributable to MZ chorionicity will depend on the direction and magnitude of its effect Prescott et al.

The question of bias is important in its own right, but has recently come to the fore, in the discussion on the missing heritability.

Monochorionic twins - Wikipedia

This concerns the discrepancy between the magnitude of twin-based heritability estimates and the, appreciably lower, amount of genetic variance explained by polygenic scores in genome-wide association studies Walter et al. Many explanations have been advanced to account for this discrepancy Eichler et al.

relationship between zygosity and chorionicity

Studies of the effects of chorionicity on a wide range of physical and psychological phenotypes have produced mixed results, with the possible exception of birth weight, for which a well-established result is the greater resemblance in birth weight of DCMZs versus MCMZs Melnick et al. Many studies are characterized by small sample sizes, and heterogeneity with respect to age of the twins. Here we present results of the analysis of 66 phenotypes, observed in relatively large samples of MZ twins, who were followed from birth into young adulthood.

We consider height and weight, attainment of motor development milestones, infant temperament, personality measures, dimensions of psychopathology, and measures of cognitive ability. If the split occurs during the first 3 days following fertilization, the pregnancy will be dichorionic DC with unconnected or fused placentas.

relationship between zygosity and chorionicity

If the division occurs 4—8 days after fertilization, the two fetuses share the same placenta but each fetus has its own amniotic fluid cavity. When the division occurs between Days 8 and 13 post-fecundation, the result is monochorionic MC monoamniotic twins with fetuses sharing the same placenta and amniotic fluid cavity. In triplet pregnancies, diagnosis of chorionicity and amnionicity is established by comparing each triplet with one another by sequential analysis: One zygote can therefore produce two or three embryos through successive division.

  • Monochorionic twins

The number of placentas and shared amniotic fluid cavities depends on the time of the division. We know that MC triplets are always MZ. The true incidence of MZ triplets is of biological, clinical and epidemiological relevance. Zygosity can be of great significance in the field of prenatal diagnosis and genetic counseling.

relationship between zygosity and chorionicity

The knowledge of zygosity is helpful in instances where chorionicity remains indeterminate and is likely to influence clinical management, e. In the field of biology, the study of twinning in triplets following spontaneous conceptions, ovulation induction and IVF may help us to understand the mechanism of monozygosity.

At the present time, assisted reproduction technology ART is the only biological mechanism capable of influencing MZ twinning Hall, Equally important, recent studies have illustrated that mono- or dichorionicity in triplet pregnancies is clearly implicated in adverse perinatal outcomes Adegbite et al. This study has served as the accepted base value for monozygosity in relevant literature since Derom et al. Machin and Bamforth also reported a series of 15 consecutive sets of SC triplets, using highly polymorphic DNA marker analysis.

Determining gestational age and chorionicity - Multiple Pregnancy - NCBI Bookshelf

Their approach of the zygotic splitting rate was particularly interesting because it permitted an analysis of the rate of monozygosity not in the general population but within the population of triplet pregnancies itself. The purpose of the present study was to evaluate the rate of monozygosity in a series of 53 consecutive sets of triplets, with a complete assessment of zygosity by analyzing highly polymorphic DNA microsatellite markers of each triplet.

Distribution of zygosity and chorionicity was studied simultaneously as a function of their mode of conception. Our results were discussed and compared with data from the literature. Materials and Methods Case eligibility Between March and Februaryevery set of triplets in which at least one of the children, live- or stillborn, weighed g or more, and with a gestation period of at least 22 weeks, was used in the study.

relationship between zygosity and chorionicity

Triplet pregnancies resulting from embryo reductions of high-order multiple pregnancies HOMP were excluded from the study. Triplet pregnancies presenting discordance in final anatomopathological chorionicity and molecular zygosity were also excluded.