[Studies on the clinical significance of the placental implantation site and the change of placental volume by uterine contraction (author's transl)].

Using ultrasonography, the influence of placental implantation site on the fetal position, duration of gestation, duration of labor, etc. was investigated on 321 patients in the 3rd trimester. Moreover, the change of placental volume in connection with the uterine contraction was also studied and the following results were obtained. 1) As for the placental implantation site, it was found on the posterior uterine wall in 139, on the anterior 97, right lateral 55, and on the left lateral in 30. 2) When the placenta was implanted at the uterine cornus, more fetuses were with breech presentation, and when it was found on the lateral site, the fetuses were with the position facing the placenta. 3) In multiparae, the gestational duration was longer when the placenta was implanted on the right side of uterus than on the left or anterior side. (p less than 0.05) 4) Placental implantation site had no relation with labor duration, fetal weight, placental weight, amount of haemorrhage during labor and cord-coiling. 5) During uterine contraction, the placental volume did not change when the pressure was 30 mmHg. During contraction, when the pressure was 50 mmHg, the placental volume became less by 30 cm3 than during interval. During interval, intraplacental blood volume wa 177 cm3.