Abstract
OBJECTIVE: To investigate the association between pre-pregnancy body mass index (BMI) and the risk of macrosomia through a preconception-early pregnancy-birth cohort in China. METHODS: Among the 12,254 women initially recruited between July 2018 and December 2021, a total of 11,438 (drop out rate: 6.66%) mother-infant pairs were included in the final analysis after excluding participants with missing data on key variables or lost to follow-up. We collected basic demographic characteristics and lifestyle behavior information of the subjects through questionnaires and practical measurements, and conducted further follow-up for pregnancy outcomes. The study assessed the association between pre-pregnancy BMI-defined categories (underweight, normal weight, overweight, and obesity) and macrosomia using multivariable logistic regression models, adjusting for sociodemographic characteristics, lifestyle behaviors, and maternal clinical factors during pregnancy. A linear trend test was also conducted. Moreover, we utilized restricted cubic spline models with three knots (placed at the 10th, 50th, and 90th percentiles of BMI) and polynomial regression to investigate the non-linear relationship of pre-pregnancy BMI with macrosomia. RESULTS: A total of 11,438 subjects were included in this study, among whom 645 infants were diagnosed with macrosomia, resulting in a prevalence of 5.64%. The results indicated that, compared with the normal weight group, overweight women had a significantly higher risk of macrosomia (odds ratio (OR) = 1.66, 95% CI [1.35-2.01]), as did obese women (OR = 1.66, 95% CI [1.13-2.45]), while underweight women had a significantly lower risk (OR = 0.55, 95% CI [0.41-0.73]). A similar association pattern between pre-pregnancy BMI and grade 1 macrosomia was observed, consistent with that for overall macrosomia. The use of restricted cubic splines revealed that the prevalence of macrosomia/grade 1 macrosomia increased with rising pre-pregnancy BMI. Furthermore, when we stratified the data by covariates, the nonlinear relationship between pre-pregnancy BMI and macrosomia/grade 1 macrosomia persisted. The results of the polynomial regression showed a gradual increase in fetal birth weight with increasing pre-pregnancy BMI levels. CONCLUSIONS: Pre-pregnancy overweight and obesity were associated with higher risks of macrosomia. Therefore, these findings suggest that promoting healthy weight management before conception may be an effective public health strategy to reduce the risk of macrosomia and improve perinatal outcomes.