Transvaginal sonographic evaluation of first‐trimester placenta previa

Abstract

Our objective was to determine the relationship between the placenta and the internal cervical os in the first trimester. This study included ultrasound examinations performed between 9 and 13 weeks' gestation over a 28‐month period. The position of the lower edge of the placenta with respect to the internal cervical OS was recorded for each transvaginal ultrasound examination. A total of 77 out of 1252 (6.2%) patients had a first‐trimester placenta previa; four cases persisted until term. There were no false‐negative diagnoses. Our conclusion is that approximately 6.2% of patients will have a placenta previa in the first trimester. Transvaginal sonography can exclude a diagnosis of placenta previa after 9 weeks' gestation. The likelihood that a placenta previa will persist until term increases if the placenta covers the internal cervical os by ≥ 1.6 cm. Copyright © 1995 International Society of Ultrasound in Obstetrics and Gynecology Copyright © 1995 International Society of Ultrasound in Obstetrics and Gynecology