Background: Pregnancy weight gain is linked to neonatal birth weight and early-life adiposity measures. Elevated weight gain during pregnancy is associated with an increased risk of offspring developing obesity-related diseases in the long term. Objectives: The objective of this study is to explore the association between pre-pregnancy   BMI, maternal weight gain during pregnancy, and neonate birth weight. Subjects and methods: This retrospective cohort study was conducted between January 2023 and January 2024 in Baghdad. The study included data from 360 healthy pregnant women from four primary healthcare centers. Gestational weight gain was computed by subtracting pre-pregnancy weight from maternal weight at the end of pregnancy. Subgroups were established to assess gestational weight gain adequacy, including inadequate, adequate, and excess categories. Gestational age was determined based on the last menstrual cycle or the first ultrasound, and the date of birth. Newborns birth weights and gestational age at birth were analyzed according to WHO growth charts. We defined two groups of abnormal growth: small for gestational age (weight below the 10^th percentile) and large for gestational age (weight above the 90^th percentile).Results: Maternal age was 27.5 ± 5.7 years. Pre-pregnancy BMI was 26.5 kg/m². Gestational weight gain averaged 11.2 kg, with 30.8% inadequate, 36.1% excess, and 33.1% adequate. The majority of neonates were adequate for gestational age (63.3%), while 35.8% were large for gestational age and 0.8% were small for gestational age. Overweight ladies had an OR of 1.77 (95% CI: 1.06, 2.98) with a p-value of 0.030, suggesting a significant increase in the risk of having a large gestational-age baby compared to normal-weight ladies. Similarly, obese women had a substantially higher risk, with an OR of 3.07 (95% CI: 1.73, 5.49) and a highly significant p-value of less than 0.001. Conclusion: The current study concludes that the increase in BMI before pregnancy and the presence of excessive weight gain during gestation could potentially function as predictive factors for the birth of neonates who are large for gestational age.

Keywords: Pre-pregnancy BMI; gestational weight gain; neonatal birth weight