Introduction
A higher neonatal morbidity and mortality rate is described for twin pregnancies compared to singleton pregnancies, particularly in the case of monochorionicity and regarding the second born twin. In this study it is examined whether the chorionicity has an impact on the fetal outcome, with special attention given to the outcome of the second twin.
Material and methods
This retrospective cohort study analyzed 2624 twins who were delivered at a Level I Perinatal Center in Germany between 2000 and 2020. Fetal parameters including biometric measurements and parameters of the physiological status were included in the analysis and were evaluated according to chorionicity. A subgroup analysis including exclusively vaginal deliveries evaluated the duration of birth, the intertwin interval, and the frequency of an unplanned cesarean delivery of the second twin.
Results
1062 (80.9 %) pregnancies were dichorionic and 250 (19.1 %) were monochorionic. Monochorionic twins revealed significantly lower values in biometric measurements and parameters of the physiological status. Considering the second born twins, monochorionic twins delivered by cesarean section had lower birth weight than dichorionic resulting from lower gestational age at birth. The birth weight of vaginally born second twins was not significantly different according to chorionicity. Independently of the mode of delivery, there was no significant difference in indicators for fetal distress between monochorionic and dichorionic second born twins.
Conclusions
Chorionicity has no effect on any neonatal outcome considering vaginally born second twins. If there are no primary indicators for a cesarean section, vaginal delivery can also be recommended for monochorionic twins since no worse outcome, especially regarding the second twin, is expected.