Intisar Ali Mohammed
Department of Obstetrics and Gynaecology, Faculty of Medicine and Health Sciences, Sana'a University
Placenta previa is the implantation of the placenta partly or entirely in the lower segment of the uterus1. Major placenta previa is when placental edge touches or covers internal cervical os. It is one of the main causes of vaginal bleeding in the third trimester 2 and a significant cause of maternal3,4 and prenatal morbidity and mortality5,6. Women with placenta previa present with painless vaginal bleeding after twenty weeks, but before delivery of baby2 . The bleeding is usually mild and recurred but sometimes can be massive and life threatening on the mother and the fetus.
The incidence of placenta previa is 3- 5 per 1000 pregnancies worldwide and is still rising because of increasing caesarean section rate. The incidence is much.
higher at twenty weeks than at 36 weeks and above. This is because as pregnancy advances the lower uterine segment is formed; the upper segment enlarges and moves with the placenta1, 2,7-10.A meta- analysis review by Ananth et al7 showed that in 36 studies, 13992 of 3700000 women who were pregnant had placenta previa. The reported incidence was approximately 1 in 200 pregnancies (range 0.28 to 1.96%). Eight cohort and 7
case-control studies showed an increased risk of placenta previa for women who had previous cesarean deliveries (OR 2.6, 95% CI 2.3 to 3.0).The review suggests that women who have experienced cesarean delivery may be 2-3 times more likely to develop placenta previa than other women and that this increased risk is further exacerbated by additional cesarean delivery. They also note that as