Intrapartum assessment of the postdate fetus.

Continuous monitoring of fetal heart rate (FHR) and routine sampling of fetal scalp blood were utilized to evaluate the intrapartum performance of 82 fetuses of postdates pregnancies. A comparison was made between this group and 260 term pregnancies. The incidences of abnormal FHR patterns were not different between the postdates group and the control group. All of the postdates neonates with low 5 minute Apgar scores had passed meconium. The mean pH values of the postdates fetuses with meconium were significantly lower than those of the control group at each sampling interval (i.e., early labor, late labor, and umbilical artery). Those fetuses with thick meconium had significantly lower pH values in late labor than did those with thin meconium. Continuous electronic FHR monitoring is recommended for intrapartum surveillance of all postdates patients. Because of the increased incidence of fetal acidosis in the presence of thick meconium, sampling of fetal scalp blood is not unreasonable even with a normal FHR pattern.