Gestational weight gain standards based on the women enrolled in the Fetal Growth Longitudinal Study of the INTERGROWTH-21st Project : a prospective longitudinal cohort study

Abstract

OBJECTIVE To describe maternal gestational weight gain (GWG) patterns in healthy pregnancies with good maternal and perinatal outcomes of women enrolled in the Fetal Growth Longitudinal Study of the INTERGROWTH-21st Project. DESIGN Prospective, longitudinal, observational multi-country study.SETTING Eight geographically diverse urban regions in Brazil, China, India, Italy, Kenya, Oman, UK and USA, April 2009 to March 2014. PARTICIPANTS Healthy, well-nourished and educated women, enrolled in the Fetal Growth Longitudinal Study component of the INTERGROWTH-21st Project, who had a body mass index (BMI) of ≥18.50 to ≤24.99 kg/m2 in the first trimester of pregnancy.MAIN OUTCOME MEASURES Maternal weight was measured using standardised methodology and identical equipment every 5±1 weeks from the first antenatal visit (<14+0 weeks’ gestation) to delivery. After ensuring that data from the study sites could be pooled, a multi-level, mixed effect, linear regression analysis for repeated measures, adjusted for gestational age was applied to produce the GWG values. RESULTS The within-site variance (59.6%) was six times higher than the between-sites’ variance (9.6%). Total mean GWG at 40 weeks’ gestation was 13.7 (SD 4.5) kg for women with a normal first trimester BMI. Fitted 3rd, 10th, 25th, 50th, 75th, 90th, and 97th smoothed GWG centiles by exact week of gestation are provided with equations for the mean and standard deviation to calculate any desired centiles according to gestational age in exact weeks. CONCLUSIONS This is the largest standardised study of healthy, well-nourished women ever to monitor GWG prospectively in a multi-country setting. The centiles generated are very robust and should help guide recommendations on optimal GWG worldwide.