**Background:** Gestational weight gain (GWG) is a natural and necessary process that includes the fetus, placenta, amniotic fluid, uterine and breast growth, expansion of blood volume and extracellular fluid, and maternal body fat reserves. Tracking GWG is an essential component of antenatal care because deviations from recommended ranges are associated with adverse outcomes. Insufficient GWG is linked to low birth weight, prematurity, small-for-gestational-age (SGA) births, and neonatal mortality. Excessive GWG is associated with gestational diabetes, hypertensive pregnancy syndromes, postpartum weight retention, cesarean delivery, macrosomia, large-for-gestational-age (LGA) births, and childhood obesity. Until 2022, Brazil lacked its own GWG curves and relied on the Chilean Atalah curve and the US Institute of Medicine (IOM) 2009 recommendations. The Atalah curve used outdated BMI cutoff points that disagreed with WHO standards since 1995 and classified some excessive weight gain as adequate, potentially contributing to the obesity epidemic among Brazilian women. The IOM recommendations were developed for North American women in a high-income country context. To address these limitations, Brazilian researchers developed population-specific GWG curves and recommendations using data from the Brazilian Maternal and Child Nutrition Consortium (CONMAI).
**Methods:** The new GWG curves were created using data from 7,086 apparently healthy Brazilian women who participated in 21 studies conducted in Brazil between 1990 and 2018, published in 2021. Four cumulative GWG curves were developed according to pre-pregnancy BMI category: underweight (BMI < 18.5 kg/m²), normal weight (BMI ≥ 18.5 and < 25.0 kg/m²), overweight (BMI ≥ 25 and < 30 kg/m²), and obesity (BMI ≥ 30 kg/m²). Optimal GWG ranges were defined based on percentiles associated with reduced risk of SGA births, LGA births, prematurity, and excessive weight retention at 6 and 12 months postpartum, using data from CONMAI and the Food and Nutrition Surveillance System. The proposed ranges were discussed and endorsed by specialists, Ministry of Health technicians, and health professionals in a workshop held in Brasília in June 2022, and adopted by the Ministry of Health on August 3, 2022.
**Key Results:** The new GWG recommendations provide trimester-specific cumulative weight gain ranges for each pre-pregnancy BMI category. For underweight women (BMI < 18.5): 0.2–1.2 kg in the 1st trimester, 5.6–7.2 kg by 27 weeks, and 9.7–12.2 kg by 40 weeks (P18–P34). For normal weight women (BMI ≥ 18.5 and < 25): −1.8–0.7 kg in the 1st trimester, 3.1–6.3 kg by 27 weeks, and 8.0–12.0 kg by 40 weeks (P10–P34). For overweight women (BMI ≥ 25 and < 30): −1.6–−0.05 kg in the 1st trimester, 2.3–3.7 kg by 27 weeks, and 7.0–9.0 kg by 40 weeks (P18–P27). For women with obesity (BMI ≥ 30): −1.6–−0.05 kg in the 1st trimester, 1.1–2.7 kg by 27 weeks, and 5.0–7.2 kg by 40 weeks (P27–P38). The curves and guidelines were created for adult pregnant women (over 18 years) in low-risk singleton pregnancies. No specific guidelines exist for different degrees of obesity. Three tools were created to facilitate adoption: an interactive online panel, an Excel calculator for z-score and percentile calculation, and an Android/iOS application (PesoGestBR).
**Clinical Implications:** Health professionals should calculate pre-pregnancy BMI using reported or early-pregnancy weight (up to 8 weeks) and height, classify according to WHO cutoff points, select the appropriate tracking curve, and calculate GWG at each visit as current weight minus pre-pregnancy weight. The marking on the curve indicates whether gain is within recommended ranges (darker areas), above, or below. Professionals should advise pregnant women on maintaining adequate gain or adjusting to reach recommended values. The authors emphasize that following GWG recommendations is important for maternal and pregnancy outcomes, and that pregnant women should be served with cordiality and without stigma regarding their nutritional condition. The recommendations should be widely disseminated and used by health professionals performing antenatal care across Brazil.