Associations of gestational weight gain with birth weight outcomes in early pregnancy weight loss women: Findings from the Beijing Birth Cohort Study.

Objective: To explore the relationship between gestational weight gain (GWG) and birth weight outcomes and establish suggested GWG patterns in early pregnancy weight loss women.

Methods: This retrospective study was conducted based on the Beijing Birth Cohort Study from 2014 to 2021 and included 20 688 women. Weight change in early pregnancy was calculated using weight measurements within 16 weeks of gestation. Multivariable logistic regression was used to analyze the relationships of different GWG categories, based on the Chinese standard, and birth weight outcomes. The statistical-based approach was used to determine the optimal GWG ranges and weekly weight gain.

Results: Compared to 3313 women who gained appropriate weight in early pregnancy, 2614 women who lost weight in the same period increased the risk of small for gestational age (SGA) (OR = 1.43, 95% CI: 1.14-1.80, P = 0.002). However, the relationship disappeared after adjusting for total GWG. Among the early pregnancy weight loss women, both excessive GWG and inadequate GWG were associated with adverse birth weight outcomes after adjusting for confounders. The suggested GWG range and rate were 11.0 ~ 16.0 kg and 0.46 to 0.67 kg/week from 16 weeks to delivery for women with normal body mass index (BMI) and weight loss in early pregnancy.

Conclusion: Weight loss in early pregnancy was not the independent risk factor of birth weight outcomes. GWG may offset the expected effects. To achieve optimal outcomes, women with normal BMI and weight loss in early pregnancy need to have a higher weight gain rate in mid-late pregnancy but similar total GWG ranges with the Chinese standard for general women.