One or multiple previous cesarean sections are associated with similar increased frequency of placenta previa

The purpose of this study was to determine whether multiple previous cesarean sections would be associated with a higher frequency of placenta previa in subsequent deliveries than in women with only one previous cesarean section.

Data of all pregnant women and deliveries were obtained from the computerized records of our department for the period 1985-1992. The study group included symptomatic placenta previa diagnosed by real time ultrasound or during labor. The data included maternal age, gravidity, parity and previous cesarean sections. Nulliparous women were excluded from the study.

There were 58,633 deliveries during the study period, including 284 patients with placenta previa (0.48%). Increasing maternal age was associated with a higher frequency of placenta previa. Similar results were found with increasing parity. A more significant trend was found with increasing number of previous abortions. Among placenta previa deliveries 21.1% of patients had previous cesarean section, and among normal deliveries only 10.9% had previous cesarean section (P < 0.0001). The frequency of placenta previa in women with previous normal deliveries was 0.79/1000; in women with one previous cesarean section 15.39/1000; with two previous cesarean section 13.91/1000; with three previous cesarean sections 10.37/1000. While the difference between none and one previous cesarean sections was highly significant (P < 0.0001), the difference between one and more cesarean sections was not significant.

Although the rate of placenta previa was significantly lower among deliveries without previous cesarean section in comparison with deliveries with one previous cesarean section, this difference was not enhanced with the increasing number of previous cesarean sections.