Evolution of Ultrasound Characteristics of Placenta and Fetal Position and Presentation in Normal Pregnancies. - Revista Brasileira de Ginecologia e Obstetrícia

Purpose: to evaluate the ultrasound characteristics of normal pregnancies, according to the placental maturity, local of insertion and thickness, fetal presentation and position during the second half of pregnancy. Methods: a descriptive study was perfomed, including at least 120 measures in each gestational age, in 2,868 normal pregnant women from Campinas, Brazil, studied through routine obstetric ultrasound examinations, with fetal biometry and placental evaluation, applying Grannum, Berkowitz, Hobbins (1979) criteria for placental maturity. Placental thickness was measured at the cord insertion site. Results: grade 0 placentas were more frequent up to 31 weeks and grade I after 32 weeks. Grade II did not appear until 32 weeks and grade III was more frequent after 36 weeks. The placental thickness significantly increased with gestational age and the most frequent placental locations were anterior and posterior. The cephalic presentation was the most frequent all gestational ages, with only 1% of breech presentation at term. The most frequent fetal position was fetal spine left side, followed by right side. Conclusions: the studied factors showed a similar distribution to that expected for normal populations and could be used as a standard for the Brazilian population.