(105) Maternal anemia and fetal heart rate tracing abnormalities in labor: associated neonatal and maternal outcomes

To investigate the relationship of maternal anemia in labor before delivery with abnormal fetal heart rate tracing characteristics (FHRT) and composite neonatal and maternal adverse outcomes (CNAO/CMAO).

Study Design:

FHRTs of all deliveries over a 15-month period at a level IV center were reviewed by physicians blinded to maternal and neonatal outcomes. In 20-minute segments, the last hour of available FHRT was analyzed. Term, singleton, non-anomalous deliveries who underwent a trial of labor were included. Anemia was defined as hematocrit < 30% at admission. Each FHRT feature was independently categorized as present if noted greater than 50% of the time in the hour before delivery. The primary outcome was the rate of CNAO or CMAO, with secondary outcomes including rates of FHRT abnormalities as defined by ACOG.  The chi-square test was used to compare groups, with p-value < 0.05 considered significant.

Results:

Of 5,160 consecutive deliveries, 3,166 (61%) met the inclusion criteria, of which 391 (14.1%) had anemia. There were no differences in oxytocin induction/augmentation rate or neuraxial anesthesia. Anemia was not associated with an increased proportion of any individual FHRT features. There was an increase in CMAO (6.8 vs 15.1%; p < 0.001), driven by an increase in the rate of blood transfusion (1.7 vs 11.5%; p < 0.001). Anemia was not independently associated with increased CNAO, or umbilical artery pH < 7.0. There was a lower rate of cesarean delivery for abnormal FHRT (9.6% vs 6.4%; p=0.04).

Conclusion:

Anemia in labor was not associated with any individual FHRT abnormalities or ACOG FHT Category. There was no change in CNAO, but there was an increased rate of CMAO driven by higher rates of maternal blood transfusion. Our findings provide additional support to other studies that found that maternal anemia was not associated with adverse neonatal outcomes.