The Association Between Pre-pregnancy Body Mass Index and Obstetric and Neonatal Outcomes Among Pregnant Women Attending Antenatal Care at Somdej Phra Yupparat Wiang Sa Hospital
Keywords:
Pre-pregnancy BMI, Overweight, Obesity, Large for gestational age, Pregnancy outcomesAbstract
Background: Pre-pregnancy body mass index (BMI) is associated with pregnancy outcomes, and metabolic risk may occur at lower BMI levels in Asian populations than under global BMI criteria. Evidence from Thailand comparing normal-weight, overweight, and obesity categories according to WHO Western Pacific Region criteria remains limited.
Objective: To examine the association of normal weight, overweight, and obesity before pregnancy with obstetric and neonatal outcomes among Thai pregnant women.
Methods: This retrospective cohort study included singleton pregnancies receiving antenatal care and delivering at Somdej Phra Yupparat Wiang Sa Hospital between October 1, 2022, and September 30, 2025. Among 1,365 women with BMI data, 176 underweight women were excluded, leaving a final cohort of 1,189 women: 497 with normal weight, 212 with overweight, and 480 with obesity. Delivery and neonatal outcomes were evaluated in 1,132 women with complete outcome data. Multivariable logistic regression was used to estimate adjusted odds ratios (aORs) and 95% confidence intervals (CIs).
Results: Compared with normal weight, obesity was associated with gestational diabetes mellitus (aOR 1.98; 95% CI 1.12–3.48) and hypertensive disorders of pregnancy (aOR 2.53; 95% CI 1.37–4.66), whereas overweight was not significantly associated with either outcome. The odds of a large-for-gestational-age infant were significantly higher in both the overweight (aOR 2.75; 95% CI 1.47–5.14) and obesity groups (aOR 3.71; 95% CI 2.19–6.27).
Conclusion: Higher pre-pregnancy body mass index was associated with adverse pregnancy outcomes, with different patterns across body mass index categories. Obesity was associated with gestational diabetes mellitus, hypertensive disorders of pregnancy, and large for gestational age infants, whereas overweight was associated with large for gestational age infants. These findings support early risk assessment before pregnancy and during early antenatal care.
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