Abstract
BackgroundThe relationship between maternal hemoglobin (Hb) levels during pregnancy and birth outcomes has been controversial. Changes in Hb level during pregnancy may have an impact on birth outcomes. This study aimed to investigate whether changes in Hb levels from early to mid- or late pregnancy is associated with birth outcomes.MethodsParticipants were singleton mothers who delivered at the National Center for Child Health and Development between 34 and 41 weeks of gestation in 2010 and 2011 (n = 1,986). Hb levels were measured at three time points: early (<16 weeks), mid- (16–27 weeks), and late (28–36 weeks) pregnancy. Associations between changes in Hb levels from early to mid- or late pregnancy and birth outcomes (birth weight, Z-score of birth weight, placental weight, and placental ratio) were assessed by multiple regression, adjusting for maternal and fetal covariates.ResultsA smaller reduction in Hb levels from early to mid- or late pregnancy was significantly associated with lower birth weight, Z-score of birth weight, placental weight, and placental ratio. Compared to women with an intermediate reduction from early to late pregnancy, women with the least reduction had a significantly increased risk of delivering low birth weight (LBW) (adjusted odds ratio [aOR], 2.0; 95% confidence interval [CI], 1.3-3.1) and small-for-gestational-age (SGA) (aOR, 1.6; 95% CI, 1.04-2.3) infants, while women with the greatest reduction had a significantly decreased risk of delivering SGA (aOR, 0.38; 95% CI, 0.23-0.65) infants, but an increased risk of high placental ratio (aOR, 1.7; 95% CI, 1.2-2.5).ConclusionsHb changes from early to mid- or late pregnancy were inversely associated with birth weight, placental weight, and placental ratio.
Highlights
The relationship between maternal hemoglobin (Hb) levels during pregnancy and birth outcomes has been controversial
The results indicate that a +1 g increase in Hb from early to late pregnancy was associated with a −76.1 change in birth weight (g), a −0.21 change in Z-score of birth weight, a −26.1 change in placental weight (g), and a −4.0 change in placental ratio (x1000), in the adjusted model
In this study, we found that changes of Hb levels from early pregnancy were significantly inversely associated with birth weight, Z-score of birth weight, placental weight, and placental ratio in pregnant Japanese women
Summary
The relationship between maternal hemoglobin (Hb) levels during pregnancy and birth outcomes has been controversial. This study aimed to investigate whether changes in Hb levels from early to mid- or late pregnancy is associated with birth outcomes. It has been reported that Hb levels at “mid- or late” pregnancy are inversely associated with birth weight and placental weight [3,6,9,10]. Plasma volume increases by 10 to 15 percent at 6 to 12 weeks of gestation and increases rapidly thereafter until 30 to 34 weeks [11,12] This induces a modest decrease in Hb levels during pregnancy. The impact of changes in Hb levels from early to mid- or late pregnancy on birth outcomes has not been investigated in detail
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