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

AIMS

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/m ) in Japan.

METHODS

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 ≤ 5.7 kg, 5.7 kg < Q2 ≤ 7.2 kg, 7.2 kg < Q3 ≤ 8.8 kg, and 8.8 kg < Q4. Clinical characteristics and outcomes were compared using the t-test, chi-square test, and multivariable logistic regression analysis.

RESULTS

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.

CONCLUSIONS

In UPW, GWG at 30 weeks of ≤5.7 kg and ≤7.2 kg are associated with preterm birth and SGA rates, respectively.