Gestational weight gain charts for different body mass index groups for women in Europe, North America, and Oceania

BACKGROUND: Gestational weight gaindiffers according to pre-pregnancy body mass indexand is related to the risks of adverse maternal and child health outcomes. Gestational weight gaincharts for women in different pre-pregnancy body mass indexgroups enable identification of women and offspring at risk for adverse health outcomes. We aimed to construct gestational weight gainreference charts for underweight, normal weight, overweight, and grades 1, 2 and 3 obese women and to compare these charts with those obtained in women with uncomplicated term pregnancies. METHODS: We used individual participant datafrom 218,216 pregnant women participating in 33 cohorts from Europe, North America, and Oceania. Of these women, 9065 (4.2%), 148,697 (68.1%), 42,678 (19.6%), 13,084 (6.0%), 3597 (1.6%), and 1095 (0.5%) were underweight, normal weight, overweight, and grades 1, 2, and 3 obese women, respectively. A total of 138, 517 women from 26 cohorts had pregnancies with no hypertensive or diabetic disorders and with term deliveries of appropriate for gestationalage at birth infants. Gestational weight gaincharts for underweight, normal weight, overweight, and grade 1, 2, and 3 obese women were derived by the Box-Cox t method using the generalized additive modelfor location, scale, and shape. RESULTS: We observed that gestational weight gainstrongly differed per maternal pre-pregnancy body mass indexgroup. The median (interquartile range) gestational weight gainat 40 weeks was 14.2 kg (11.4-17.4) for underweightwomen, 14.5 kg (11.5-17.7) for normal weight women, 13.9 kg (10.1-17.9) for overweight women, and 11.2 kg (7.0-15.7), 8.7 kg (4.3-13.4) and 6.3 kg (1.9-11.1) for grades 1, 2, and 3 obese women, respectively. The rate of weight gainwas lower in the first half than in the second half of pregnancy. No differences in the patterns of weight gainwere observed between cohorts or countries. Similar weight gainpatterns were observed in mothers without pregnancy complications. CONCLUSIONS: Gestational weight gainpatterns are strongly related to pre-pregnancy body mass index. The derived charts can be used to assess gestational weight gainin etiological research and as a monitoring tool for weight gainduring pregnancy in clinical practice.