Researchers performed this meta-analysis of individual participant data from 25 pooled cohort studies and 196,670 participants in order to assess how gestational weight gain (across a range of prepregnancy weights) is associated with maternal and infant outcomes. Outcomes revealed an association of prepregnancy weight and the magnitude of gestational weight gain with risk for any adverse outcome (defined as ≥1 of the following: preeclampsia, gestational hypertension, gestational diabetes, cesarean delivery, preterm birth, and small or large size for gestational age at birth). Optimal gestational weight gain estimation may help in prenatal counseling; however, limited predictive value was noted of the optimal gestational weight gain ranges for the outcomes assessed.

• This individual participant-level meta-analysis included 25 cohort studies from Europe and North America (main study sample).
• For each prepregnancy body mass index (BMI) category, they estimated optimal gestational weight gain ranges by selecting the range of gestational weight gain that was associated with lower risk for any adverse outcome.
• From 3505 participants within 4 separate hospital-based cohorts, they used individual participant-level data as a validation sample.
• Collection of data was done between 1989 and 2015.
• In December 2015, they performed the final follow-up.
• The presence of 1 or more of the following outcomes-preeclampsia, gestational hypertension, gestational diabetes, cesarean delivery, preterm birth, and small or large size for gestational age at birth-was the main outcome determined, termed as adverse outcome.

• The main sample included 196,670 women; median age was 30.0 years [quartile 1 and 3, 27.0 and 33.0 years] and 40,937 of these were white.
• At baseline, 7809 (4.0%) of these were categorized as underweight (BMI <18.5); 133,788 (68.0%) had normal weight (BMI, 18.5-24.9); 38,828 (19.7%) were overweight (BMI, 25.0-29.9); 11,992 (6.1%) were with obesity grade 1 (BMI, 30.0-34.9); 3284 (1.7%) were with obesity grade 2 (BMI, 35.0-39.9); and 969 (0.5%) were with obesity grade 3 (BMI, ≥40.0).
• Overall, 37.2% (n = 73,161) of women experienced any adverse outcome, ranging from 34.7% (2706 of 7809) among women categorized as underweight to 61.1% (592 of 969) among women categorized as obesity grade 3.
• For women categorized as underweight, optimal gestational weight gain ranges were 14.0 kg to less than 16.0 kg; for normal weight, 10.0 kg to less than 18.0 kg; for overweight, 2.0 kg to less than 16.0 kg; for obesity grade 1, 2.0 kg to less than 6.0 kg; for obesity grade 2, weight loss or gain of 0 kg to less than 4.0 kg; and for obesity grade 3, weight gain of 0 kg to less than 6.0 kg.
• Outcomes revealed association of these gestational weight gain ranges with low to moderate discrimination between those with and those without adverse outcomes (range for area under the receiver operating characteristic curve, 0.55-0.76).
• In the validation sample, researchers noted similar results for discriminative performance to the corresponding results in the main study sample (range for area under the receiver operating characteristic curve, 0.51-0.79).