The perinatal outcomes by gestational weight gain range at 30 weeks of gestation among pre-pregnancy underweight women.

Abstract

To evaluate the perinatal outcomes by gestational weight gain (GWG) range at 30 weeks of gestation among underweight pregnant women (pre-pregnancy body mass index ≤ 18.5 kg/m2 ) in Japan. This retrospective study was conducted at a hospital in Japan from 2003 to 2020. The underweight pregnant women (UPW; n= 3643) were divided into quartile groups based on the weight gain at 30 weeks of gestation: group Q1 ≤ 5.7kg, 5.7kg < Q2 ≤ 7.2kg, 7.2kg < Q3 ≤ 8.8kg, and 8.8kg < Q4. Clinical characteristics and outcomes were compared using the t-test, chi-square test, and multivariable logistic regression analysis. The cumulative incidences of preterm births were 7.5% (n= 70), 5.0% (n= 45), 5.4% (n= 50), and 4.9% (n= 44), and the birth rates of small for gestational age (SGA) infants were 15.7% (n= 147), 9.6% (n= 87), 6.9% (n= 64), and 5.9% (n= 53) in Q1, Q2, Q3, and Q4, respectively. Multivariable analysis revealed that Q1 was significantly associated with preterm births (adjusted odds ratio [aOR]=1.6; 95% confidence interval [CI]=1.0-2.3), and Q1 and Q2 were significantly associated with SGA (adj. OR=3.0; 95% CI=2.2-4.3; adj. OR=1.7; 95% CI=1.2-2.5, respectively). None of the quartile groups were significantly associated with the incidence of primary cesarean sections, gestational diabetes mellitus, and macrosomia. In UPW, GWG at 30 weeks of ≤5.7kg and ≤7.2kg are associated with preterm birth and SGA rates, respectively.