Fetal Doppler hemodynamic changes in spontaneous versus prostaglandin E1-induced active labor

Background. To assess fetal hemodynamic changes before and during active labor, either spontaneous or prostaglandin E₁ (PGE₁)-induced labor. Materials and methods. This is a prospective longitudinal study and a cohort of 49 healthy women at 37-41⁺ weeks gestation without signs of fetal distress was investigated until in labor. One group of 23 healthy women had spontaneous active labor, the second group of 26 women was in active labor induced by an intra-cervical administration of PGE₁ for elective induction. Blood flow waveform indices (S/D ratio, RI, PI) were assessed by pulsed Doppler ultrasonography from the umbilical artery (UA) and fetal middle cerebral artery (MCA) before and in labor. Both groups were compared for the waveform indices and perinatal outcome including duration of labor, meconium stain, baby sex, birthweight, UA blood gas measurements at delivery, Apgar's scores, prolonged nursery stay (≥ 5 days), and NICU admission. Results. Demographic data of the two groups were comparable. During spontaneous active labor, the S/D ratio and RI became significantly decreased in the UA (p <0.05) and the three waveform indices were decreased more in the MCA (p <0.01, 0.005, 0.05, respectively) compared with those measured before labor. During PGE₁-induced active labor, all the waveform indices were not significantly decreased in either the UA or the MCA. The occurrence of abnormal UA blood gas values was significantly more in the PGE₁-induced group than in the spontaneous labor group (23.1% vs. 4.3%; p <0.05). No other adverse perinatal outcomes were observed in either group. Conclusions. Decreasing impedance in both the UA and MCA during spontaneous labor is a physiological fetal adaptation to labor to prevent fetal cerebral hypoxia by maintaining adequate brain blood flow during normal parturition. This fetal adaptation phenomenon was not observed in the group of PGE₁-induced labor with the result of a high incidence of abnormal UA blood gas values.