TRANSVAGINAL SONOGRAPHY;
FIRST TRIMESTER;
PLACENTA;
INTERNAL CERVICAL OS;
D O I:
10.1046/j.1469-0705.1995.05050301.x
中图分类号:
O42 [声学];
学科分类号:
070206 ;
082403 ;
摘要:
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 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 greater than or equal to 1.6 cm.