Weight gain in women of normal weight before pregnancy: complications in pregnancy or delivery and birth outcome

Objective: To investigate the relation between gestational weight gain in women of normal prepregnant weight and complications during pregnancy and delivery in a population with high gestational weight gain and birth weight.

Methods: Healthy women (n = 615) of normal weight before pregnancy (body mass index 19.5-25.5 kg/m(2)) were randomly selected. Maternity records gave information on age, height, prepregnant weight, gestational weight gain, parity, smoking, gestational hypertension and diabetes, preeclampsia, delivery complications, and infants' birth size and health.

Results: The mean weight gain in pregnancy was 16.8 +/- 4.9 kg (mean +/- standard deviation). A total of 26.4% of the women had complications, either in pregnancy (9.1%) or delivery (17.3%). Women gaining weight according to the recommendation of the Institute of Medicine (11.5-16.0 kg) had lower frequency of pregnancy-delivery complications than women gaining more than 20.0 kg (P =.017), but did not differ significantly from those gaining 16-20 kg (P >.05). When dividing weight gain in pregnancy into quintiles, a relative risk of 2.69 (95% confidence interval 1.01, 7.18, P =.048) was found for complications in pregnancy in the fourth quintile (17.9-20.8 kg), using the second quintile as reference (12.5-15.5 kg). The mean birth weight was 3778 +/- 496 g. A low weight gain in pregnancy (less than 11.5 kg) was associated with an increased frequency of infants weighing less than 3500 g at birth (P <.01).

Conclusion: A gestational weight gain of 11.5-16.0 kg (Institute of Medicine recommendation) for women of normal prepregnant weight is related to the lowest risk for pregnancy-delivery complications. In the population studied, the upper limit might be higher (up to 18 kg), and low weight gain should be avoided to optimize birth outcome.