Fetal acidosis and the abnormal fetal heart rate tracing: the term breech fetus.

The intrapartum fetal heart rate tracings of 27 terms fetuses in breech presentation were analyzed to evaluate their immediate neonatal outcome. The tracings were quantitatively evaluated for comparison with Apgar scores and umbilical cord gases at delivery. Of the 27 cases, 12 had monitoring strips that scored 4 or less before birth. The P50 for acidosis at delivery (an umbilical artery pH of 7.25 or less) was 55 minutes for an intrapartum tracing that scored 4 or less. Fetuses with intrapartum tracings scoring 8 or more throughout labor had normal Apgar scores and cord gases. In comparing the present data with those of a previous study of vertex presentations, the authors found that given similar tracings, the breech fetus deteriorates more rapidly than the vertex fetus. Cesarean section is recommended if delivery is not imminent in a laboring breech and the intrapartum tracing deteriorates to score 4 or less.