Material and Method: Uncomplicated normal pre-pregnancy BMI Thai singleton pregnant women with less than 16 weeks’ gestation participated in this study between June 2008 and September 2009. Serial measurements of maternal and fetal weight using ultrasound examination were recorded every four weeks from 16 to 36 weeks’ gestation.

Results: Two hundred seventy four uncomplicated pregnant women were included in this study of which 166 met inclusion criteria during a period of the study. There was a signifi cant correlation between gestational weight gain and both estimated fetal weight gain and actual infant birth weight (p < 0.05). Using the multiple regression analysis, gestational weight gain between 16 to 28 weeks’ gestation, multiparity, and male infants were independent factors and were signifi cantly correlated with both fetal weight gain and actual infant birth weight (p < 0.05).

Conclusion: For pregnant women with normal pre-pregnancy BMI, gestational weight gain can predict intrauterine fetal weight as well as infant birth weight.

Keywords: Infant birth weight, Fetal weight, Gestational weight gain, Pre-pregnancy BMI