Hemoglobin Concentrations and Prevalence of Anemia During Pregnancy: Results from the Brazilian Maternal and Child Nutrition Consortium

Background: Anemia is common among pregnant women from low- and middle-income countries, but national estimates are scarce. Objectives: We aimed to assess hemoglobin (Hb) concentrations and the anemia prevalence in Brazil. Methods: Data included 12,287 pregnant women aged 15-49 y and 17,967 measurements from 7 studies (2007-2014) participating in the Brazilian Maternal and Child Nutrition Consortium. Hb (g/dL) was obtained from medical records (6 studies, 17,565 measurements) or capillary blood samples (1 study, 402 measurements). Hb <11, <10.5, and <11 g/dL were used to define anemia at the first, second, and third trimesters using the 2024 WHO guideline. Identification of implausible Hb values and heterogeneity analysis were performed. We estimated medians and interquartile ranges for the Hb concentration and prevalence and 95% confidence intervals (CI) of anemia according to maternal prepregnancy BMI, age, and education, gestational trimester, and year of data collection. Results: Median Hb was 12.0 (95% CI: 11.2, 12.8) g/dL; no differences were observed according to the studied covariables. Anemia prevalence was 14.1% (95% CI: 13.6, 14.6), and highest during 2013 [27.9% (95% CI: 17.3%, 38.6%)] and in the third trimester [23.5% (95% CI: 22.5%, 24.6%)]. Higher anemia prevalence in the third compared with the first trimester was also observed among women aged 15-19 [1st: 8.02% (95% CI: 6.2%, 9.9%); 3rd: 28.1% (95% CI: 25.4%, 30.8%)] than those aged 20-49 y [1st: 6.5%; (5.8%, 7.2%); 3rd: 22.6% (95% CI: 21.4%, 23.7%)]. Anemia prevalence for those with education ≤4 y (15.9%; 95% CI: 14.1%, 17.8%) and women with prepregnancy underweight (19.2%; 95% CI: 15.9%, 22.4%) and normal weight (15.3%; 95% CI: 14.4%, 16.2%) were higher than those with 9-11 (13.1%; 95% CI: 12.4%, 13.8%) and 12-18 y (10.3%; 95% CI: 9.2%, 11.0%), and overweight (12.2%; 95% CI: 10.8%, 13.6%) and obesity (9.9%; 95% CI: 8.1%, 11.7%). Conclusions: Anemia was higher in adolescents compared with older women and in the third trimester compared with the first, underscoring the need for targeted monitoring during these periods.