Material and Method: All medical records of women who gave birth at Lerdsin Hospital between October 1, 2010 and September 30, 2013 were reviewed. Three thousands six hundred eighty three women who met inclusion criteria were divided into four categories according to pre-pregnancy body mass index (BMI) as underweight, normal weight, overweight and obese. Women in each categories were compared for outcomes (neonatal birth weight, cesarean birth, pregnancy induced hypertension (PIH), gestational diabetes (GDM), preterm birth, low birth weight (LBW), macrosomia, small for gestational age (SGA) and large for gestational age (LGA)), using logistic regression to calculate odds ratios (ORs) and 95% confidence intervals (CIs).

Results: Of 3,683 pregnant women, 34.9% had weight gain within, 36.5% above, and 28.7% below IOM guidelines. Women with higher gestational weight gain in all BMI categories had an increased risk of cesarean birth (except in obese group), macrosomia, LGA and a decreased risk for preterm birth, LBW (except for overweight group) and SGA. Women with lower gestational weight gain had an increased risk for preterm birth, LBW, SGA and a decreased risk for cesarean birth. Neonates delivered from women whose gestational weight gains were above IOM guidelines were also heavier than those from neonates whose maternal weight gains during pregnancy were within IOM guidelines.

Conclusion: The IOM guidelines are useful for monitoring gestational weight gain and if it were within guidelines, women could have decreased risk for several adverse outcomes such as cesarean birth, macrosomia, LGA, preterm birth, LBW and SGA.

Keywords: Institute of Medicine (IOM), Pre-pregnancy BMI, Gestational weight gain (GWG), Cesarean birth, Preterm birth, Low birth weight (LBW)