581 Achieving maternal weight gain recommendations and its impact on cervical length shortening in twin gestations

Abstract

To determine if underachievement of recommended maternal weight gain in twin gestations is associated with a shortened mid-trimester transvaginal cervical length (TVCL). Retrospective cohort study of twin gestations receiving TVCL surveillance between 2003 and 2010. Each woman was categorized as having achieved vs underachieved recommended maternal weight gain at delivery using institutional BMI and gestational age- specific weight gain guidelines for women carrying twins. TVCL measurements were routinely obtained between 18-24 weeks’ gestation and the shortest of three measurements acquired were compared between groups. Poisson regression was used to calculate adjusted relative risks (aRR) and 95% confidence interval (CI) of TVCL<15mm controlling for maternal race, cerclage, prior preterm birth, and pre-pregnancy BMI. 304 patients met inclusion criteria with 160 (52.6%) achieving and 144 (47.4) underachieving recommended weight gain guidelines during their study pregnancy. Women who underachieved had significantly shorter median TVCL (37 vs 40mm; p=.003; Figure 1). There were higher rates of TVCL <30mm (26.4% vs 17.5%; p=.061), <25mm (16.0% vs 11.3%; p=.229), and <20mm (11.8% vs 6.3%; p=.09), but these did not reach statistical significance in either the adjusted or unadjusted analysis. However, underachieving weight gain remained significantly associated with a shortened TVCL <15mm (9% vs 2.5%; aRR 3.2, CI 1.2-8.6) after adjusting for confounders. Underachievement of recommended maternal weight gain was also significantly associated with preterm birth <34 weeks’ gestation (58.7% vs 33.3%; p<0.001). Inadequate maternal weight gain in twin gestations independently contributes to a shortened mid-trimester cervical length which is strongly associated with prematurity. The mechanism is currently unknown; however, poor maternal nutrition may be a modifiable risk factor influencing pathologic premature cervical change.