Anticipation of uterine bleeding in placenta previa based on vaginal sonographic evaluation

The aim of this study was to predict massive uterine bleeding during pregnancy and cesarean section in women with placenta previa using transvaginal ultrasonography.

Transvaginal ultrasonography was performed prospectively at and after 28 gestational weeks with follow-up scans at 5- to 7-day intervals until cesarean section in 35 women with placenta previa. The patients were classified into 3 groups based on the following sonographic features of the placental edge in relation to the internal cervical os: type A = two thirds of the placenta from the placental center overlapping the internal os (13 cases); type B = one third of the placenta from the periphery to outside overlapping the internal os (10 cases), and type C = echo-free space (EFS) in the placental edge overlapping the internal os (12 cases). In some cases of type-A placentas, lacunae with blood flow in the placenta from the basal plate to the chorionic plate were also observed. All types were further subdivided based on the presence or absence of associated sponge-like echo (S-echo) in the wall of the uterus adjacent to the placental location. In each type, the relation with the amount of bleeding during hospitalization and preterm delivery was examined.

Incidences of sudden massive bleeding during hospitalization were 7.7% (1/13), 10.0% (1/10), and 83.3% (10/12), in types A, B and C, respectively, being significantly higher in type C (p < 0.01). The risk of antepartum massive bleeding was also significantly higher in type C (p < 0.01). The incidence of preterm delivery due to sudden massive bleeding and the amount of bleeding during cesarean section were significantly higher in type A + S and type A + S with lacunae, respectively.

Sonographic EFS in the lower edge of the placenta overlying the cervix indicates the risk of sudden massive antepartum bleeding. Furthermore, lacunae with sponge-like echo may also reflect the risk of massive bleeding at cesarean section. These findings warrant further observational studies to verify their clinical implications.