Preconception Hemoglobin Concentration and Risk of Low Birth Weight and Small-for-Gestational-Age: A Large Prospective Cohort Study in China

Abstract

Less is known about the impact of maternal preconception anemia on birth outcomes. We aimed to examine associations between preconception hemoglobin (Hb) concentrations with risk of low birth weight (LBW) and small-for-gestational-age (SGA). This study was from a large population-based prospective cohort in China and included 124,725 women with singleton live births delivered at gestational ages of 28–45 weeks who were registered before pregnancy. Maternal Hb concentrations were measured during registration, and other health-related information was recorded prospectively. Logistic regression was used to evaluate the associations between preconception Hb concentrations with risk of LBW and SGA, adjusting for potential confounders. The results showed women with preconception anemia accounted for 22.28%. The incidences of LBW/SGA were 2.37%/6.30% among anemic women, and 2.01%/5.48% among non-anemic women, respectively. Preconception mild anemia increased by 17% (95% confidence interval (CI): 1.06, 1.28) and 14% (95% CI: 1.07, 1.21) the risk for LBW and SGA, while moderate-to-severe anemia had no significant association with LBW and SGA. Compared with the 120–129 g/L group, a U-shaped association was observed between preconception Hb concentrations with LBW and SGA. In conclusion, not only maternal anemia but also elevated Hb concentrations before pregnancy contribute to an increased risk of LBW and SGA.

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

“…Meanwhile, the mean Hb concentrations around 100 and 140 g/L were classified into 6 categories using intervals of 10 g/L: <100 g/L, 100~109 g/L, 110~119 g/L, 120~129 g/L, 130~139 g/L and ≥140 g/L. A similar classification was also reported in some other studies [30,31].…”

The Long-Term Effect of Maternal Iron Levels in the Second Trimester on Mild Thinness among Preschoolers: The Modifying Effect of Small for Gestational Age

“…This finding was in line with a systematic review that indicated a heightened risk of FGR was associated with maternal iron deficiency during pregnancy [ 31 ]. Additionally, two extensive prospective studies conducted in China reported an increased risk of SGA linked to maternal iron deficiency, anemia, and malnutrition during pregnancy [ 48 , 59 ]. Previous animal experiments also indicated that inadequate maternal iron intake during gestation impaired placental and fetal development through altering placental trophoblast differentiation in rats [ 60 ].…”

Nationwide-free preconception care strategy: Experience from China

“…In addition, there is a U-shaped relationship between hemoglobin concentration and adverse outcomes, according to many studies generated from the National Preconception Health Examination Project in China. Both severe anemia and a hemoglobin concentration higher than 150 g/L prior to pregnancy were associated with an increased risk of spontaneous abortion ( 64 ), very early preterm birth ( 65 ), low birth weight, and small for gestational age infants ( 66 ). Therefore, screening for anemia during the preconception period is of great public health significance to enable timely intervention ( 67 ).…”