Relationship between pre-pregnancy maternal BMI with spontaneous preterm delivery and birth weight.

The aim of the present study was to find the relationship between pre-pregnancy maternal body mass index (BMI) with spontaneous preterm delivery and birth weight. A prospective cohort study was performed on 576 pregnant women. Maternal BMI was determined at the first prenatal visit between 8-12 weeks' gestation and considered as the pre-pregnancy maternal weight. The women were then monitored up to delivery. Out of 576 women, 396 completed the study. The demographics of the women in all BMI groups did not differ with regard to age, height, history of abortion and employment. A total of 21 women (5.3%) were underweight; 198 women (50%) were normal weight; 117 women (29.5%) were overweight and 60 (15.2%) were obese. There were no cases of morbidly obese (BMI > 40 kg/m(2)) women. Obesity in women had a positive correlation with higher gestational age at the time of delivery (r = 0.213, p = 0.015) and a heavier birth weight (r = 0.361, p = 0.008). Low birth weight had a correlation with low maternal BMI (r = 0.157, p = 0.041). Macrosomia was greater in obese women (p = 0.022) and BMI had a positive correlation with macrosomia (r = 0.224, p = 0.034). Preterm delivery showed a negative correlation with maternal BMI (r = -0.124, p = 0.004) and the women with a lower BMI had a greater number of preterm deliveries (p = 0.035).