RESUMO
AIM: To investigate the significance of gestational weight gain (GWG) in association with the spontaneous onset of labor at term. METHODS: A retrospective cohort study on 985 pregnant women (629 nullipara and 356 pluripara) who delivered singleton babies at term was conducted. We reviewed the maternal demographics (age, parity, prepregnancy body mass index [BMI]) and the perinatal outcomes (gestational age [GA] and the type [spontaneous or induced] of labor onset, and GWG). The subjects were categorized by prepregnancy BMI and GWG. The rates of spontaneous onset of labor were compared between the nullipara and pluripara groups. Kaplan-Meier survival analysis was applied to evaluate the time to spontaneous labor according to prepregnancy BMI and GWG. A Cox proportional hazards model was used to determine the independent predictive factor for spontaneous onset of labor. RESULTS: In both the nullipara and pluripara group, women with prepregnancy obesity were less likely to enter spontaneous labor. In nullipara, women with excessive weight gain were less likely to enter spontaneous labor. In pluripara, women with poor gain were more likely to enter spontaneous labor. In the multivariate model, GWG was independently associated with the spontaneous onset of labor in both nullipara (hazard ratio [HR] 0.83, 95% confidence interval [CI] 0.75-0.98, P = 0.03) and pluripara (HR 0.82, 95% CI 0.64-0.93, P = 0.005). CONCLUSION: Greater maternal weight gain was significantly associated with longer gestation and a decreased likelihood of spontaneous onset of labor at term.