In placenta previa, the placenta occupies a position near the internal os at or after 28 weeks of gestation. Ultrasound examination has been used to diagnose placenta previa in 6% of the general population during the first trimester of pregnancy. More than 90% of these cases undergo placental conversion by the third trimester. This conversion (commonly called migration) is caused by the differing growth patterns of the uterine corpus and the lower uterine segment. To correctly diagnose placenta previa, it is crucial to utilize all available ultrasound techniques, including endovaginal and translabial scanning. This retrospective study examines the timing and the techniques of follow-up ultrasound examination in placenta previa.
