TRANSVAGINAL SONOGRAPHIC EVALUATION OF FIRST-TRIMESTER PLACENTA PREVIA

Our objective was to determine the relationship between the placenta a nd the internal cervical os in the first trimester. This study include d 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 transv aginal ultrasound examination. A total of 77 out of 1252 (6.2%) patien ts had first-trimester placenta previa;four cases persisted until term . There were no false-negative diagnoses. Our conclusion is that appro ximately 6.2% of patients will have a placenta previa in the first tri mester. Transvaginal sonography can exclude a diagnosis of placenta pr evia after 9 weeks' gestation. The likelihood that a placenta previa w ill persist until term increases if the placenta covers the internal c ervical os by greater than or equal to 1.6 cm.