ObjectiveTo evaluate whether twin zygosity influences the association between neonatal outcomes and gestational weight gain (GWG) based on the Chinese guidelines in twin-pregnancy women.DesignA retrospective cohort study. And it is not a clinical trial.SettingWomen with twin pregnancies living in Wuhan, China.ParticipantsA total of 5140 women who delivered live and non-malformed twins from 1 January 2011 to 31 August 2017 were included in this study.Main outcome measureThe primary neonatal outcomes included paired small for gestational age (SGA, <10 th percentile birth weight for gestational age and sex), low birth weight (LBW, <2500 g) and gestational age (<33 weeks and <37 weeks). The association between GWG and neonatal outcomes was examined by Logistic regression analyses.ResultsA total of 5140 women were included, of whom 22.24%, 54.78% and 22.98% were below, within and above the Chinese guidelines, respectively. Among the including 10 280 infants, 26.28% of them were monozygotic (MZ) twins and 73.72% of them were dizygotic (DZ) twins. Women with low GWG had a significantly higher proportion of LBW/LBW and LBW/NBW infants, a greater likelihood of SGA/SGA and SGA/appropriate for gestational age (AGA) infants and a higher incidence of preterm birth. The associations persisted both in MZ and DZ twins, and twin zygosity influenced the degree of association between GWG and SGA, LBW and preterm birth. High GWG was associated with significant risk reductions in SGA/AGA pairs, LBW/LBW or LBW/NBW pairs, and less than 33 gestational weeks. However, high GWG was only associated with reduced risk of LBW/LBW pairs both in MZ and DZ twins.ConclusionsGWG below the Chinese recommendations increased the risk of SGA, LBW and preterm birth in both MZ and DZ twins. The effect was more pronounced in MZ twins than that in DZ twin pairs. A high GWG only reduced the risk of LBW/LBW pairs both in MZ and DZ twins.
