Reference charts for weight gain and body mass index during pregnancy obtained from a healthy cohort

Objective. To create reference charts for weight gain and body mass index (BMI) in pregnancy derived from longitudinal data obtained in a representative sample of the Argentinean population.

Methods. A prospective cohort of 1439 healthy pregnant women was selected from antenatal clinics in seven different urban regions in Argentina. Serial anthropometric measurements were made at weeks 12, 16, 20, 24, 28, 32, 36 and in the last pre-natal control. Centile curves of body weight and BMI by gestational age were developed using the LMS method.

Results. Mean weight gain at 38 weeks of gestation was 11.9 ± 4.4 kg. There were no differences in total weight gain between women who enter pregnancy with low, normal or overweight; only those women with a pre-pregnancy BMI in the range of obesity showed a significantly lower weight gain (10.2 ± 4.8 kg). At 12 weeks of pregnancy, BMI values of the 10th, 50th and 90th centiles were 19.3, 22.8 and 29.0, and at 38 weeks these values were 23.3, 27.4 and 33.8, respectively.

Conclusion. This BMI for gestational age chart, based on women who delivered normal birth weight infants and processed with modern statistical methods, represents an improvement in pre-natal care monitoring.