Intrapartum Surveillance of IUGR Fetuses with Cardiotocography and Fetal Pulse Oximetry

Abstract

Objective: To investigate the efficacy and safety of intrapartum fetal pulse oximetry, as a predictor of metabolic acidosis at birth of fetuses with intrauterine growth retardation (IUGR). Study Design: We studied 18 IUGR fetuses (group I) and a control group of 30 appropriate for gestational age (AGA) fetuses (group II) during labor. Both groups had abnormal fetal heart rate tracings and were monitored simultaneously throughout labor with cardiotocography and fetal pulse oximetry. Apgar scores, pH and base excess of fetal blood obtained from the umbilical artery after delivery were compared in both groups. Setting: The Fetal Surveillance Unit of the 2nd Department of Obstetrics and Gynecology, Aretaieion Hospital, Medical School, Athens University. Results: In IUGR fetuses, when their oxygen saturation value (FSPO₂) was less than 34%, cord artery pH was 7.10 ± 0.04, base excess –13 ± –1 mmol/l and Apgar scores ≤5 at the 5th min, and when FSPO₂ was over 35%, artery pH was 7.29 ± 0.08, base excess –8 ± –2 mmol/l and Apgar scores ≧7 at the 5th minute. In cases of drops of FSPO₂below 30% for more than 2 min, labor was completed operatively and cord pH was 7.00 ± 0.04, base excess –15 ± –2 mmol/l and Apgar scores ≤5 at the 5th minute. In AGA fetuses, when FSPO₂ was over 30%, artery pH was over 7.20, base excess <–11 mmol/l and Apgar scores ≧9 at the 5th minute; in contrast, when FSPO₂ was <30% for 2 min, a cesarean section was performed and cord pH was ≤7.02, base excess ≧–13 mmol/l and Apgar scores ≤4 at the 5th minute. Conclusions: In IUGR fetuses, FSPO₂ values less than 34% represent an acidotic status, while values of ≧35% are well tolerated. Fetal pulse oximetry proved reliable, according to umbilical cord blood measurements and Apgar scores, reducing cesarean deliveries in cases of nonreassuring cardiotocographic patterns in IUGR fetuses.