Increasing birthweight above 4000 grams is associated with adverse outcomes among births without diabetes

Objective To evaluate the association of increasing birthweight above 4,000 grams and adverse obstetric outcomes and to explore the influence of key maternal risk factors, including pre-pregnancy body mass index (BMI) and gestational weight gain (GWG), among births not complicated by diabetes. Study Design This was a retrospective cohort study of singleton, non-anomalous, live births between 37- and 42-weeks’ gestation in the United States between 2012-2021. Births complicated by diabetes or with birthweights less than 3000 gams were excluded. Births were stratified into four weight categories: 3000-3999 grams (referent group), 4000-4499 grams, 4500-4999 grams and ≥5000 grams. We performed stratified analyses by pre-pregnancy BMI and GWG per National Academy of Medicine guideline recommendations. Analyses were performed via chi-squared and adjusted incidence risk ratios for statistical comparisons. Results There were 23,487,820 births included in this analysis. Higher birthweights were significantly associated with higher risk of adverse perinatal outcomes, including cesarean delivery, blood transfusion, unplanned hysterectomy, maternal ICU admission and obstetric anal sphincter injury. Additionally, the adjusted risk of all adverse neonatal outcomes also increased with increasing birthweight. When stratified by maternal risk factors including BMI and GWG groups, we similarly found higher risk of adverse outcomes among higher birthweight categories, particularly among births complicated by maternal obesity or GWG above NAM recommendations. Conclusion Among births without diabetes, birthweights above 4,000 grams were associated with increasingly higher risk of adverse perinatal outcomes, and adverse outcomes remained higher even after stratification by BMI and GWG.