Effect of Previous Cesarean Section on Ultrasound Doppler Studies of Placental Circulation and Pregnancy Outcome.

Objectives: To primarily determine the effect of a previous cesarean section on Doppler studies of the uterine artery, umbilical artery, and umbilical vein. Patients and Methods: This prospective study was conducted on singleton pregnancies between 18 and 22 weeks of gestation, including both women with and without a previous cesarean section. Doppler studies of the uterine artery, umbilical artery, and umbilical vein indices were performed during mid-trimester fetal ultrasound scans. Doppler indices and pregnancy outcomes were compared between the two groups. Results: A total of 351 pregnancies, including 74 women with a previous cesarean section and 277 women with an unscarred uterus, underwent Doppler studies. The uterine artery pulsatility index (PI) and resistance index (RI) were significantly higher in women with a previous cesarean section (p < 0.001). Moreover, both univariate and multivariate analyses demonstrated that a previous cesarean section was significantly associated with an increase in uterine artery PI, RI, and the rate of abnormal uterine artery PI, defined as values above the 95th percentile (p = 0.034). Other Doppler study results, as well as pregnancy outcomes, were comparable between the two groups. Conclusions: Pregnant women with a previous cesarean section have significantly higher uterine artery resistance, and a higher rate of abnormal uterine artery PI during mid-pregnancy. Therefore, a cesarean section may be detrimental to uterine arterial health. However, no significant adverse clinical outcomes were observed.