Evaluation of fetal intrapartum hypoxia by middle cerebral and umbilical artery Doppler velocimetry with simultaneous cardiotocography and pulse oximetry.

OBJECTIVE: To investigate fetal circulation at different stages of hypoxia during labor, and to study blood flow alterations in the brain and peripheral tissues, through simultaneous use of three non-invasive techniques. MATERIALS AND METHODS: Ninety two pregnant women between 38 and 41 weeks of gestation, comparable for maternal age and parity, were simultaneously monitored with cardiotocography (CTG), continuous fetal pulse oximetry and Doppler ultrasonography during the first stage of labor. In 70 cases evaluation was successful, and useful data was obtained. Doppler waveforms were obtained before and during abnormal CTG patterns, of both the umbilical (UA) and middle cerebral artery (MCA) to measure the pulsatility index (PI), resistance index (RI), and flow velocity integral (FVI). The study population was divided in three groups, according to CTG and fetal pulse oximetry tracings: 20 term fetuses with normal CTG patterns and oxygen saturation (FSPO(2)) values >40%, 30 term fetuses with abnormal CTG patterns and FSPO(2) values between 30 and 40%, and 20 fetuses with abnormal CTG patterns and FSPO(2) values <30% for a time up to 2 min. These were studied and peripartum outcomes were compared. RESULTS: Redistribution of blood flow was noted at FSPO(2) values of 37%, in all groups. In the presence of reduced oxygen saturation (near to or below 30%), MCA Doppler showed significantly lower PI (1.06+/-0.33 vs.0.74+/-0.39, p=0.03) and RI (0.59+/-0.14 vs. 0.44+/-0.14, p=0.03), while that of the UA showed mildly higher resistance indices (0.98+/-0.14 vs. 1.28+/-0.50, p=0.01 and 0.57+/-0.12 vs. 0.79+/-0.24, p=0.004, respectively). When an oxygen saturation value of <30% was maintained for greater than 2 min, MCA Doppler indices reversed, likely indicating morbid fetal hypoxia. Differences in fetal outcomes between groups correlated with Doppler and pulse oximetry tracings. CONCLUSIONS: During active labor the fetus maintains oxygen supply to the brain by redistributing blood flow. In cases of hypoxia this is feasible for only 2 min. We note a strong correlation between fetal pulse oximetry, Doppler velocimetry of the MCA and UA, and fetal morbidity.

Intrapartum surveillance of IUGR fetuses with cardiotocography and fetal pulse oximetry.

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 < or =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 > or =7 at the 5th minute. In cases of drops of FSPO2)below 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 < or =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 > or =9 at the 5th minute; in contrast, when FSPO2 was <30% for 2 min, a cesarean section was performed and cord pH was < or =7.02, base excess > or =-13 mmol/l and Apgar scores < or =4 at the 5th minute. CONCLUSIONS: In IUGR fetuses, FSPO2 values less than 34% represent an acidotic status, while values of > or =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.