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Twin study: relationship between birth weight, zygosity, placentation, and pathologic placental changes.
M A Ramos-Arroyo1, T M Ulbright, P L Yu
1Department of Medical Genetics, Indiana University School of Medicine, Indianapolis.
Acta Geneticae Medicae Et Gemellologiae
|January 1, 1988
Summary
Placental chorion status significantly impacts twin birth weight, with dichorionic placentas associated with higher weights. Monochorionic placentas, exclusively from monozygotic twins, frequently exhibit vascular connections and cord insertions, supporting trophotropism theory.
Area of Science:
- Obstetrics
- Developmental Biology
- Perinatology
Background:
- Twin gestations present unique placental considerations.
- Understanding placental morphology is crucial for fetal development outcomes.
Purpose of the Study:
- To investigate the relationship between placental chorionicity, zygosity, and birth weight in like-sexed twins.
- To analyze the occurrence of vascular anastomoses and umbilical cord insertions in relation to placental type.
Main Methods:
- Examination of 182 placentas from like-sexed live-born twins.
- Classification of placentas as monochorionic or dichorionic.
- Analysis of zygosity, birth weights, vascular anastomoses, and umbilical cord insertions.
Main Results:
- Monochorionic placentas (40.1%) were exclusively from monozygotic (MZ) twins; dichorionic placentas (59.9%) included 28.9% MZ pairs.
- Dichorionic and dizygotic (DZ) twins exhibited the highest birth weights, suggesting chorion status is a key determinant.
- Vascular anastomoses were present in 79.5% of monochorionic placentas.
- Monochorionic placentas showed a higher incidence of velamentous and marginal umbilical cord insertions (27.4%) compared to dichorionic placentas (13.8%).
Conclusions:
- Placental chorionicity is a more significant factor in twin birth weight than zygosity.
- The findings support the theory of trophotropism, indicating close embryonic apposition influences placental growth and vascularization.