Unselected low-risk pregnancies and the effect of continuous intrapartum fetal heart rate monitoring on umbilical blood gases and cerebral palsy

OBJECTIVE: Our purpose was to evaluate the clinical validity of electronic fetal heart rate monitoring to detect fetal acidemia and to evaluate the prevalence of cerebral palsy in unselected low-risk pregnancies. STUDY DESIGN: We selected two secondary and two tertiary level institutions in which 10,030 infants were born. Among them, 5546 of the pregnancies were low-risk pregnancies by antepartum evaluation. The fetal heart rate patterns were interpreted according to the guidelines of the National Institute of Child Health and Human Development. The correlations between the fetal heart rate pattern and umbilical blood gases and the fetal heart rate pattern and cerebral palsy were studied. Spastic cerebral palsy was diagnosed at > or =1 year by pediatric neurologists. Statistics included unpaired t test, contingency table with chi(2) and Fisher tests, and one-way analysis of variance with Bonferroni/Dunn test. RESULTS: On the basis of the severity of decelerations, frequency of decelerations, and decreased variability, umbilical pH, and Po(2) level were decreased accordingly, and incidence of pH<7.1 was increased. Sensitivity and false-positive rate of nonreassuring fetal heart rate patterns for fetal acidemia were 63% and 89%. There were nine cerebral palsy cases: six of the cases were preexisting asphyxia before monitoring was initiated, two of the cases were cytomegaloviral infections, and one of the cases was a maternal amniotic fluid embolism. CONCLUSION: In low-risk pregnancies, intrapartum fetal heart rate monitoring was useful to detect fetal acidemia. Cerebral palsy caused by intrapartum asphyxia was restricted to unavoidable accidents under continuous fetal heart rate monitoring.