The clinical significance of asymptomatic mid-trimester low placentation diagnosed by ultrasound.

A prospective investigation of the problem of low placentation in mid-trimester, in uncomplicated pregnancies was performed. 773 pregnant women were included and 70 (9.1%) had a low-positioned placenta, defined as a placenta reaching or partially covering the cervical os, diagnosed by ultrasound between the 19th and 21st week of pregnancy. In no case did the placenta completely cover the cervical os. By repeat ultrasound examination in the 36th week of pregnancy, all low placentations had converted to normal position. Low placentation in mid-trimester was not associated with pregnancy complications or neonatal complications. A placenta reaching or partially covering the cervical os, in early pregnancy, seems to be normal, not influencing the subsequent course of pregnancy.