[Sonographically detectable changes in placental structures in pregnancy. 2. Statistical comparison of the frequency distribution of placenta stages 0-3 newborn infants with a birth weight of 2,500-3,999 grams].

1200 examinations of sonographical demonstrable placental ripeness were done in 552 pregnant women. The frequency of stages 0 to 3 as compared with aid of O. Bunke's confidence intervals. Stage 0 were found frequently until the 30. week of pregnancy, stage 1 between the 21. and 36. gestational week, stage 2 between the 33. and 38. week of pregnancy and stage 3 between the 35. and 40. week. The comparison of the areas of unsharpness several stages possibly may give informations about the period of pregnancy when the stages coincide.