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Electronic fetal monitoring changes in the setting of maternal anemia

      Objective

      Anemia is a commonly diagnosed comorbidity in pregnancy that is associated with an increased risk of fetal complications. However, recent work from our group demonstrated that maternal anemia was associated with higher umbilical artery O2 content at the time of delivery. Given this, we aimed to examine the relationship between maternal anemia and electronic fetal monitoring (EFM) patterns associated with fetal hypoxia.

      Study Design

      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 ≤ 11.0 g/dl on admission. The primary outcome was composite high-risk Category II EFM in the last 60 minutes before delivery (recurrent late and/or variable decelerations, minimal variability, tachycardia, or >1 prolonged deceleration); the secondary outcomes were total deceleration area (TDA) and TDA > 90th percentile. Outcomes were compared between patients with and without anemia. Multivariable logistic regression was used to adjust for potentially cofounding factors.

      Results

      Of the 8,196 patients with admission CBC and EFM data, 2,672 (32.6%) were anemic and 5,524 (67.4%) were not. After adjusting for induction of labor and hypertensive disorders of pregnancy, patients with anemia were significantly less likely to have composite high-risk Category II features on EFM [34.2% vs 32.0%, aRR 0.93, 95% CI 0.86-0.99]. Women with anemia also had decreased TDA and were less likely to have TDA >90% [18.7% vs. 16.2%, aRR 0.85, 95% CI 0.77-0.94].

      Conclusion

      Patients with anemia are less likely to have high risk EFM features associated with fetal hypoxia. This finding suggests that maternal anemia may be protective against intrapartum fetal hypoxia. This may be plausible because of adaptive mechanisms that allow for easier unloading of O2 to the placenta and compensatory increased fetal O2 extraction.
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