Birthweight is an independent predictor of birth asphyxia in twins: A retrospective cross-sectional cohort study of 5337 Chinese twins.

OBJECTIVE: Few studies are available on birth asphyxia risks in twin neonates. This retrospective multi-center cross-sectional study determined the birthweight percentiles of 5337twins and birth asphyxia incidence of the twin population. METHODS: We retrieved sociodemographic and obstetric data from the electronic records systems of participating centers. Neonate birthweight was measured within 24 h of birth. Perinatal asphyxia was diagnosed if 5-minute Apgar score was ≤5, or resuscitation was required 10 min after birth. The primary outcome was the incidence of birth asphyxia. RESULTS: Totally 5337 neonates were eligible. The mean neonatal birthweight was 2227.1 ± 608.99 g and the 5th, 50th, and 95th percentiles of birthweight were 970, 2400, and 3080 g, respectively. The mean Apgar score was 9.06 ± 1.73 at 1 min and 8.99 ± 1.74 at 5 min. Totally 13.5 % (705/5222) twins had asphyxia and 9.35 % and 4.16 % twins had moderate and severe asphyxia, respectively. Twins with a birthweight< 1500 g had the highest asphyxia rate (64.8 %) and twins with a birthweight between 2500 and 3000 g had the lowest asphyxia rate (3.6 %). Stepwise logistic regression analysis revealed that higher birthweight was associated with a significantly reduced risk of asphyxia [OR 0.772 (95 %CI 0.755, 0.789), P < 0.001]. The AUROC for mean twin birthweight was 0.86±0.01 (95 %CI 0.84, 0.88) using a cutoff of 1950 g, with a sensitivity of 0.84 and a specificity of 0.78. CONCLUSION: Twins have lower birthweight versus singletons and a significant proportion of twins, especially twins with lower birthweight, are at risk of birth asphyxia. Birthweight is an independent predictor of asphyxia and should be further explored as a predictive marker for stratifying asphyxia risks in twin neonates.