This retrospective study examined the associations between pre-pregnancy body mass index (BMI), gestational weight gain (GWG), and perinatal outcomes among women with singleton pregnancies delivering at a general hospital in Nakhon Si Thammarat Province, Thailand. Secondary data were retrieved from the HosXP electronic medical database and delivery records. Of 4659 eligible delivery records, 4051 women met the study criteria and were included in the analysis. Multivariable binary logistic regression models were used to estimate adjusted odds ratios (aORs) and 95% confidence intervals (CIs). The incidences of preterm birth, small-for-gestational-age (SGA) infants, and below-optimal head circumference (HC) were 6.99%, 18.22%, and 42.85%, respectively. Maternal underweight before pregnancy was significantly associated with increased odds of preterm birth (aOR = 1.60, 95% CI: 1.21–2.12), SGA (aOR = 1.79, 95% CI: 1.44–2.24), and below-optimal HC (aOR = 1.44, 95% CI: 1.18–1.76). Inadequate GWG was also associated with higher odds of SGA (aOR = 1.66, 95% CI: 1.38–2.00) and below-optimal HC (aOR = 1.29, 95% CI: 1.11–1.49). Conversely, maternal overweight/obesity and excessive GWG were associated with lower odds of SGA and below-optimal HC. These findings indicate that pre-pregnancy BMI and GWG were independently associated with adverse perinatal outcomes among Thai women with singleton pregnancies and may provide context-specific evidence to support maternal nutritional assessment and gestational weight monitoring during antenatal care.

Maternal anemia during pregnancy may adversely affect fetal growth, including neonatal head circumference (HC). This retrospective cohort study aimed to identify predictors of small HC among infants born to women with third-trimester anemia. Secondary data were obtained from the HosXP electronic medical database and delivery records of pregnant women who delivered between October 2020 and September 2023. A total of 934 women met the eligibility criteria and were included in the analysis. Maternal characteristics were summarized using descriptive statistics. Associations between maternal factors and neonatal HC were examined using the Chi-square test, Fisher’s exact test or Mann–Whitney U test, and independent predictors were identified using binary logistic regression analysis. The mean neonatal HC was 32.76 ± 1.50 cm, and 43.90% of infants were classified as having a small HC. Gravidity, pre-pregnancy body mass index (BMI), and gestational weight gain (GWG) were significantly associated with neonatal HC. Multivariable analysis revealed that women with two pregnancies (aOR = 0.51, 95% CI: 0.352–0.734) and those with three or more pregnancies (aOR = 0.54, 95% CI: 0.373–0.773) had lower odds of delivering infants with small HC than primigravida women. Pre-pregnancy overweight or obesity was associated with lower odds of small HC (aOR = 0.59, 95% CI: 0.426–0.805), whereas inadequate GWG increased the likelihood of this outcome (aOR = 1.38, 95% CI: 1.010–1.894). Maternal gravidity, pre-pregnancy BMI, and GWG may influence neonatal HC. These findings may support nurses in identifying women at risk, monitoring GWG, and providing targeted nutritional counseling during antenatal care.