In modern obstetrics, obstetrical hemorrhage remains a major cause of morbidity and mortality. Abnormal placentation is a prominent source of adverse outcomes in both the mother and the fetus, secondary to the potential for hemorrhage, blood transfusion, preterm delivery, and emergency hysterectomy (5). Strategies to prevent or reduce the incidence of abnormal placentation have been studied, including consideration of the relationship between prior CS and the subsequent development of placenta previa.
In this retrospective study, we reviewed the numbers and rates of placenta previa and cesarean deliveries over the last 15 years to determine temporal trends and the relationship between placenta previa and cesarean deliveries (6). The data showed that the number of deliveries per year was generally stable over time, ranging from 3,200 to 4,700. By contrast, the number of CS deliveries steadily increased from 560 in 2001 to more than 1,000 in 2015. There was a corresponding progressive increase in the CS rate from 14% to 30%. As the total number of deliveries did not increase over the study years, the increase in CS rate was likely attributed to an increasing number of repeat CS deliveries, an increasing rate of maternal requests for CS (especially with the increased rate of pregnancies arising from assisted reproductive technology and the associated increased risk of multiple gestation deliveries), and declining number of trials of labor after CS.
Although the CS rate rose progressively over the study period, the number and percentage of patients with placenta previa did not exhibit a similar trend. The placenta previa rate increased somewhat over time, but the rate did not increase in a clearly progressive pattern. Furthermore, the rate of placenta previa did not differ significantly between patients with or without a previous CS, thereby suggesting that the presence of a uterine scar alone did not affect the incidence of placenta previa.
Our results suggest additional lines of research for future studies. For example, it would be interesting to know whether the risk of placenta previa was affected by specific factors related to the primary CS, such as the timing of or indication for the prior CS. The effect of number of prior CS deliveries (single versus multiple) is another possible area of future study.7 Future analyses may include examining placenta previa rates while adjusting for these CS-related factors and patient characteristics (8,9). To further understand the development of placenta previa, it would also be interesting to evaluate tissue healing and structural changes after both normal vaginal and CS deliveries.
The maternal mortality rate of 0.77% in our patients with placenta previa is much lower than the 7% to 10% rates reported in the literature, despite 55.4% of our patients requiring emergency CS. Our low rate may be at least partially attributed to the expertise of care provided at KAUH, as a referral center for high-risk obstetric patients (10). Similar to previous reports, maternal mortality was related to massive hemorrhage and subsequent multi-organ failure (10, 11).