The association of fetal heart rate patterns with nucleated red blood cell counts at birth

OBJECTIVE: The purpose of this study was to evaluate the relationship between fetal heart rate patterns and fetal nucleated red blood cell counts. STUDY DESIGN: Data were collected prospectively from March through September 2000. Umbilical cord blood was used for nucleated red blood cell analysis. The fetal heart rate pattern was analyzed for reactivity; presence, duration, and type of decelerations; and time interval between the last acceleration and delivery. RESULTS: Two hundred seventy-nine singleton term pregnancies formed the study population, 67% of which were delivered vaginally. The median nucleated red blood cells per 100 white blood cells was 7 (range, 0-158). The univariate analysis indicated that nucleated red blood cells are correlated significantly with abnormal fetal heart rate patterns, time interval between the last acceleration and delivery, fetal growth restriction, the presence of meconium, and a 1-minute Apgar score of less than or equal to 7 However, the stepwise regression analysis identified the time interval between the last acceleration and delivery as the only variable that independently predicted elevated nucleated red blood cell count at birth (P < .0001, R-2 = 0.26). CONCLUSION: Earlier studies have demonstrated an association between adverse perinatal outcome and elevated nucleated red blood cell count. In view of the high false-positive rate that is associated with the prediction of adverse perinatal outcome by fetal heart rate abnormalities, our results support previous studies that indicate that the presence of fetal heart rate accelerations is a reliable predictor of the nonhypoxic fetus.