In this study, 56% of women bled. That seems to be pretty consistent with what I see in other studies.
Can ultrasonography of the placenta previa predict antenatal bleeding?
Authors:Hasegawa J; Higashi M; Takahashi S; Mimura T; Nakamura M; Matsuoka R; Ichizuka K; Sekizawa A; Okai T
Author Address: Department of Obstetrics and Gynecology, Showa University School of Medicine, Tokyo, Japan.Source:Journal Of Clinical Ultrasound: JCU [J Clin Ultrasound] 2011 Oct; Vol. 39 (8), pp. 458-62. Date of Electronic Publication: 2011 Jun 10.
Purpose: To evaluate the abnormal sonographic (US) findings in patient with placenta previa and bleeding.
Methods: A total of 182 cases of singleton pregnancies with placenta previa were reviewed. The US findings including the type of placenta previa, placental location, presence of placenta lacunae, lack of clear zone, sinus venosus at the margin of the placenta, velamentous cord insertion, sponge-like echo in the cervix and cervical length were evaluated in relation to episodes of bleeding that required in-patient treatment during pregnancy and/or emergency cesarean section.
Results: Episodes of antenatal bleeding occurred in 102/182 (56%) patients with placenta previa. An emergency cesarean section was performed in 66 (64.7%) of these 102 patients. In the 80 patients without episodes of antenatal bleeding, an emergency cesarean section was performed in only 1 (1.3%). Detection of US findings just prior to cesarean section was not associated with the need for emergency cesarean section due to uncontrollable bleeding from the placenta previa. Frequencies of each US finding at 20 weeks of gestation were not different between the patients who underwent emergency cesarean sections and the others. Frequency of marginal sinus was slightly higher in cases with bleeding episode (16% versus 0%, p < 0.05), but the other US findings were not associated with the occurrence of bleedingepisodes during pregnancy.
Conclusions: No US finding could predict bleeding episodes and the eventual need for an emergency cesarean section. The obstetrician should be aware that sudden bleeding during pregnancy may occur in patients with placenta previa, even in the absence of any other US findings.