Impact of chorionicity on birth weight discordance in twins.

Background: Advanced maternal age (AMA, ≥35 years) is increasing, linked to delayed childbearing and infertility, with medically assisted reproductive (MAR) technology boosting twin pregnancy rates. Birth weight discordance in twins [BWDT, birth weight discordance (∆BW) >20%] raises neonatal morbidity. Chorionicity matters: monochorionic diamniotic (MCDA) twins face higher risks from placental anastomoses, while dichorionic diamniotic (DCDA) twins have better outcomes. This study explores their association with BWDT. The aim of this study was to characterize the association of chorionicity status in twin pregnancies and BWDT.

Methods: A retrospective analysis was conducted on twin infants born between January 2011 and December 2020 at The Third Affiliated Hospital, Guangzhou Medical University, with complete birth data. The relationship between DCDA twins and the occurrence of BWDT was examined via the multivariate logistic regression analysis.

Results: A total of 3,231 pairs of twins were included, including 498 pairs in the MCDA twins group and 2,733 pairs in the DCDA twins group. In the DCDA twins group, the proportion of advanced puerperae (≥35 years old) and first conception was significantly higher than that in the MCDA twins group (P<0.05). An unconditioned logistic regression model was used to control for confounding factors, and the results indicated DCDA twins are at a lower risk for BWDT.

Conclusions: DCDA twins are less likely to have BWDT.