title: 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 > or = 1.6 cm.
authors.affiliation: Magee-Women's Hospital, Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh School of Medicine, PA 15213, USA.
authors.forename: L M
authors.initials: LM
authors.lastname: Hill
authors.forename: D M
authors.initials: DM
authors.lastname: DiNofrio
authors.forename: P
authors.initials: P
authors.lastname: Chenevey
mesh_terms: D005260:Female; D006801:Humans; D015994:Incidence; D010923:Placenta Previa / Q000000981:diagnostic imaging* / Q000453:epidemiology; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D012189:Retrospective Studies; D016216:Ultrasonography, Prenatal / Q000379:methods*