354: Does maternal anemia impact fetal oxygenation and risk of acidemia at term?

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Anemia is a commonly diagnosed comorbidity in pregnancy. It decreases oxygen (O2) carrying capacity thereby increasing the risk of complications such as fetal growth restriction and preterm delivery. The effect of anemia on O2 delivery to the fetus is unknown. This study examines the relationship between maternal anemia and fetal oxygenation status as measured by umbilical cord pO2. This is a secondary analysis of a prospective cohort study of singleton term deliveries with universal admission CBC and cord gases between 2010 and 2014. Maternal anemia was defined as hemoglobin ≤10 g/dl on admission. The primary outcomes were umbilical artery (UA) and vein (UV) pO2; secondary outcomes were acidemia (UA pH< 7.1), low UA/UV pO2 (< 5th percentile), and high UA/UV pO2 (>90th percentile). Outcomes were compared between patients with and without anemia. Multivariable logistic regression was used to adjust for confounders. Of the 7,737 patients with an admission CBC and paired cord gases, 1,108 (14%) were anemic. Maternal anemia was associated with a significantly higher UA and UV pO2 [median (IQR): UA 20 (16,24) vs 19 (15,24) mmHg, p=0.01; UV 30 (25,36) vs 29 (23,34) mmHg, p< 0.01]. Compared to neonates of nonanemic mothers, neonates born to anemic mothers were more likely to have high UV pO2 >90% (15.9% vs 10.9%; aOR 1.51, 95% CI 1.26-1.82) and were less likely to have low UA pO2 < 5% (6.1% vs 7.7%, aOR 0.74, 95% CI 0.56-0.97). UV pO2 remained higher in anemic patients after stratifying by MCV. UA pO2 was higher only in patients with normocytic anemia. Proportions of UV pO2 < 5% and UA pO2 >90% were similar between groups. Although maternal anemia was associated with a significant difference in UA pH, there was no difference in neonatal acidemia (aOR 0.90, 95% CI 0.54-1.51). UA pCO2 and lactate were lower in the anemic group. Umbilical cord O2 content is higher in anemic mothers. Maternal anemia may lead to a compensatory rightward shift in the oxygen-hemoglobin dissociation curve, allowing for easier unloading of O2 to the placenta and increased O2 transfer to the fetus.View Large Image Figure ViewerDownload Hi-res image Download (PPT)