Comparison of uterine artery waveforms during uterine contractions induced by oxytocin and prostaglandin
Background: Uterine artery waveforms are used as indicators of fetal growth restriction and pregnancy-induced hypertension; however, the findings of most reports were recorded when contractions were absent, leaving the dynamics during labor unclear. This present study aimed to investigate the effects of prostaglandin F2α (PGF2α) and oxytocin administrations on uterine artery resistance and pulsatility. Methods: This study was approved by the Ethics Committee of Kawasaki Medical School (3632) and was conducted in accordance with the ethical guidelines. The duration of the study was five years from the date of Ethics Committee approval.The participants included were 30 perinatal pregnant women who had no maternal or fetal complications admitted for delivery. The method used in inducing labor was randomly chosen (PGF2α and oxytocin were used in 15 cases each). Transabdominal ultrasonography was performed by a single experienced person to measure the uterine artery pulsatility index (PI) and resistance index (RI). The participants were divided into 3 subgroups based on cervical dilation (2-6 cm, 6-10 cm, and 10 cm to delivery). A univariate analysis was performed to evaluate the mean uterine artery PI and RI, and changes in labor stage were analyzed. The relationship between uterine artery RI and umbilical cord arterial pH was evaluated. Results: Vaginal delivery occurred in 15 and 11 cases in the oxytocin and PGF2α groups, respectively. Four babies with abnormal fetal heart rates were delivered via emergency cesarean section. There were no differences between the two groups concerning the duration of labor, bleeding during labor, placental weight, birth weight, or in cases of fetal asphyxia based on the Apgar score. No significant differences were observed in PI between the oxytocin and PGF2α groups in any of the three stages of labor(p > 0.05). In the oxytocin group, uterine arterial blood flow in terms of both RI and PI tended to be the highest at a cervical dilation of 6-10 cm. However, while a similar trend was observed for PI in the PGF2α group, RI was highest at a cervical dilation of ≥ 10 cm. No correlations were found between RI and pH at any of the cervical dilation phases(p > 0.05). Conclusion: The results of our study showed that the type of labor-inducing agent had no effect on maternal circulation. The total infusion volume of PGF2α was larger than that of oxytocin; thus, it may be preferable to use oxytocin as a conventional induction method.
