[Dynamics of changes in fetal presentation and position in late pregnancy].

The frequency of various presentations and positions of the fetus in individual gestational weeks in the third trimester was examined in 1137 pregnant women based on 1785 ultrasonic findings. Cephalic presentation at 28 weeks was observed in 62% cases and at the end of pregnancy in 95%. Breech presentation decreased from 29% to 4% before delivery, and transverse presentation was 10 times less frequent at delivery than at the beginning of the third trimester. The first and second fetal positions occurred almost equally in both of the main longitudinal presentations. Dynamics of changes regarding position and presentation was examined in 32 patients regularly each week. In 10 of them there was no presentation change and in 22, changes occurred once or several times, tending to attain a physiologic cephalic presentation before delivery. This presentation, once attained, did not change after the 33rd week. With regard to breech presentation, changes are possible even up to the 36th week. The optimal time for ultrasonic examination with the purpose of determining fetal presentation and position is 33-37 full gestational weeks.