Introduction: Placenta previa is a serious obstetric condition and a major cause of antepartum hemorrhage. When implanted over the scar of previous caeserian section scar it could lead to placenta accrete, another major cause of postpartum hemorrhage and obstetric hysterectomy. First trimester ultrasonography has not been studied thoroughly for prediction of these serious conditions.
Aim of work: To show the efficacy of first trimester placental localization in prediction of migration of low lying placenta in cases of previous cesarean section and the predriction of placenta accreta.
Patients: The study was performed on 75 cases with history of one or more cesarean sections, single fetus, with placenta either covering or within 20 mm from the internal cervical os. Maternal age group was from 20 to 40 years old.
Methodology: Patients were examined during the first visit at 11-14 weeks of gestation by trans-abdominal then transvaginal ultrasound. Direction of cord insertion to the placenta whether towards or away from the internal os was reported. Criteria of abnormal placental invasion were searched for using 2D and color Doppler ultrasound.
Patients were re-examined again during 24-32 weeks of gestation to report placental migration to the upper uterine segment. Cases that found in the lower segment within 20 mm or covering the internal os were reported as placenta previa.
Results: 87% of cases showed placental migration in third trimester. The direction of umbilical cord attachment to placenta showed highest sensitivity in prediction of placenta previa when recorded early in first trimester in comparison to the distance from the leading placental edge to the center of the internal os and placental position.
Conclusion: First trimester localization of placenta by ultrasonography could predict placenta previa in cases with a history of previous cesarean section and low lying placenta.Direction of cord insertion to the placenta and sonographic criteria of abnormal placental invasion are valuable criteria in predicting placenta previa. Ultrasonography in late first trimester could suspect abnormal placental invasion but it doesn’t definitively diagnose placenta accreta because it is histopathological diagnosis.