[Placenta previa--from the past to the present].

The author present contemporary methods for diagnosis of placenta praevia. He compare old methods as X-ray placentography, radioisotope placentography with using ultrasound to determine the location of placenta. Placenta praevia can be diagnosed prenatally using ultrasound through transabdominal, afterwards with transvaginal ultrasound. This decrease prolonged hospitalization and needless Cesarian section. The author made parallel between frequency in beginning of pregnancy with frequency at term. With advance of gestational age the frequency of placenta praevia decrease. This decreasing incidence with increasing gestational age is attributable to the concept of placental migration. When the placental edge was inicially > 2 cm from cervical os, migration occurred in all cases and no Cesarean sections were necessary for placenta praevia. When the placenta overlapped the cervical os by > 20 mm at 26 weeks, all the women required Cesarian delivery. The author present basic strategies to reduce maternal and fetal mortality and morbidity from placenta praevia. All pregnant women should have a routine sonogram at 20 weeks gestation. When the area over the internal os cannot be identified, a transvaginal sonogram should be performed. Women who have a lower placental edge which is < 1 cm from internal os should have a sonogram at about 34-35 weeks gestation. When placenta praevia is present should be perform prior Cesarian delivery.