Objective: To determine whether inadequate gestational weight gain in the second trimester in twin pregnancies is associated with an increased risk of preterm birth (PTB) at <32 weeks.
Study design: Retrospective cohort study including 489 twin pregnancies delivered between 2001 and 2013. Rates of weight gain at different gestational ages were compared with Institute of Medicine guidelines.
Result: An inadequate rate of weight gain at <20 weeks was not associated with PTB. Patients with inadequate rates of weight gain at 20 to 28 weeks had a higher risk of PTB at <32 weeks (37.6%) compared to those with adequate weight gain (15.2%) (P<0.001). In multivariate analysis, women with inadequate weight gain at 20 to 28 weeks were 2.8 times more likely to deliver at <32 weeks (95% confidence interval 1.65 to 4.81).
Conclusion: Inadequate gestational weight gain at 20 to 28 weeks in twin pregnancies was the strongest predictor of PTB at <32 weeks. This represents an optimal time for interventions to improve weight gain and potentially decrease rates of PTB.