U-Shaped Association between Maternal Hemoglobin and Low Birth Weight in Rural Bangladesh

Abstract

Low birth weight (LBW) is associated with a higher risk of neonatal mortality and the development of adult-onset chronic disease. Understanding the ongoing contribution of maternal hemoglobin (Hgb) levels to the incidence of LBW in South Asia is crucial to achieve the World Health Assembly global nutrition target of a 30% reduction in LBW by 2025. We enrolled pregnant women from the rural Tangail District of Bangladesh in a Maternal Newborn Health Registry established under The Global Network for Women’s and Children’s Health Research. We measured the Hgb of pregnant women at enrollment and birth weights of all infants born after 20 weeks gestation. Using logistic regression to adjust for multiple potential confounders, we estimated the association between maternal Hgb and the risk of LBW. We obtained Hgb measurements and birth weights from 1,665 mother–child dyads between July 2019 and April 2020. Using trimester-specific cutoffs for anemia, 48.3% of the women were anemic and the mean (±SD) Hgb level was 10.6 (±1.24) g/dL. We identified a U-shaped relationship where the highest risk of LBW was seen at very low (< 7.0 g/dL, OR = 2.00, 95% CI = 0.43–7.01, P = 0.31) and high (> 13.0 g/dL, OR = 2.17, 95% CI = 1.01–4.38, P = 0.036) Hgb levels. The mechanisms underlying this U-shaped association may include decreased plasma expansion during pregnancy and/or iron dysregulation resulting in placental disease. Further research is needed to explain the observed U-shaped relationship, to guide iron supplementation in pregnancy and to minimize the risk of LBW outcomes.

Iron and Folic Acid Supplementation in Pregnancy: Findings from the Baseline Assessment of a Maternal Nutrition Service Programme in Bangladesh

“…The national estimate of pregnancy anaemia in Bangladesh suggests that nearly half of women were anaemic [ 7 ]. A recent study in Tangail, a rural district of Bangladesh, identified a 48% prevalence of anaemia in pregnant women [ 8 ]. According to the national estimate, the prevalence of anaemia in women was higher in rural areas (45%) than in urban areas (36%) [ 7 ].…”

The Associations of Maternal Hemoglobin Concentration in Different Time Points and Its Changes during Pregnancy with Birth Weight Outcomes

“…A study from Norway also reported that increased Hb levels were associated with lower placental weight and impaired fetal growth [46]. Abnormally high Hb concentrations during pregnancy usually indicate poor plasma volume expansion, which also leads to an increased risk of LBW [20,21,41,47]. In addition, high Hb might increase blood flow resistance, which reduces maternal blood perfusion and leads to placental dysplasia [48].…”

Maternal Anemia in Third Trimester and Low Birth Weight (LBW): Systematic Review

“…In addition, it is known that fetal growth is significant and that this trimester sees the greatest intake of iron and other micronutrients. Anemia during pregnancy is independently associated with low birth weight due to a lack of iron stores to support placental growth and fetal development and appropriately expand red blood cell mass (20).…”