Association of maternal BMI during early pregnancy with infant anemia: a large Chinese birth cohort

BACKGROUND: Infant anemia is prevalent in low- and middle-income countries. Maternal body mass index (BMI) is associated with serum ferritin in cord blood, but as yet has not been linked to infant anemia. The objective of this study was to examine the association of maternal BMI during early pregnancy with infant hemoglobin levels and anemia at 6 and 12 months in a Chinese birth cohort. METHODS: The prospective cohort included 17,193 mother-infant pairs. Maternal weight and height prior to 20 gestational weeks as well as infant hemoglobin at 6 and 12 months were measured following standard procedures, and BMI was calculated as weight in kilograms divided by the square of height in meters. Women were categorized into underweight, normal weight (reference), overweight, and obesity. Infant anemia was defined as hemoglobin < 11.0 g/dl. Fractional polynomial regression was used to examine the relation between maternal BMI and infant hemoglobin, joinpoint regression to identify breakpoints, and logistic regression to estimate odds ratios (ORs). RESULTS: In the cohort, 1160 (6.8%) were anemic at 6 months and 904 (5.3%) at 12 months. An inverse U-shaped relation of maternal BMI with infant hemoglobin was found at 6 months, at their maximum at maternal BMI of 22.4 kg/m(2), and a similar relationship found again at 12 months. Maternal obesity rather than underweight was associated with an increased risk of anemia for infants at 6 months (adjusted OR 1.39, 95% CI 1.02, 1.88), but not at 12 months. Maternal anemia during mid-pregnancy augmented the risk at 6 months (adjusted OR 2.91, 95% CI 1.14, 7.46), but did not mediate the association (Z = − 1.102, P = 0.270). CONCLUSIONS: Maternal BMI during early pregnancy is correlated with infant hemoglobin in an inverse U-shaped profile, and obesity increases infant anemia risk that is aggravated by maternal anemia during pregnancy. This study enriched the epidemiological evidence on the adverse effect of high maternal BMI on long-term health of offspring. Optimizing maternal weight in obstetric care is necessary to improve offspring health.