[Ultrasonographic study of low-lying placenta and its clinical significance].
Low-lying placenta is reported to cause PROM, preterm labor, and abnormal bleeding during pregnancy and labor, but it has not been clearly defined how low the placenta has to be implanted to categorize it as "low-lying". In the present investigation, using ultrasonography, the distance between the placental implantation site and the internal cervical os in relation to gestational outcome was investigated to clarify the diagnosis and clinical significance of low-lying placenta. 1. Placental implantation site in normal gestation 1) In none of the cases at week 28 of gestation or later, the distance was 2cm or less between the lower edge of the placenta and the internal cervical os. At week 32 or later, the distance was 3cm or less in none. 2) At week 36 or later, it was 5 cm or more in all cases. 2. Low-lying placenta in association with gestational or labor outcome When "low-lying placenta" was tentatively defined as the placenta implanted within 2cm from the internal os and "normal placenta" as one implanted 2.1 cm or more from the internal os, the following findings were obtained. 1) The incidence of low-lying placenta was 2.8% (49/1,771) at gestational weeks 20 < or = - < 24, 0.96% (17/1,771) up to gestational week 29, and 0.73% (13/1,771) up to 1 week prior to labor. 2) The incidence of bleeding during gestation, preterm labor, PROM and emergency C/S was higher in the 13 cases with low-lying placenta remaining until labor than in 1,749 cases (p < 0.05) normally sited.(ABSTRACT TRUNCATED AT 250 WORDS)
Obata
S
S
Department of Obstetrics and Gynecology, Nippon Medical School, Tokyo.
Ishihara
K
K
D002585:Cesarean Section; D005260:Female; D006801:Humans; D007744:Obstetric Labor Complications; D010923:Placenta Previa / Q000000981:diagnostic imaging*; D011247:Pregnancy; D011256:Pregnancy Outcome; D011262:Pregnancy Trimester, Second; D011263:Pregnancy Trimester, Third; D016216:Ultrasonography, Prenatal / Q000379:methods; D014592:Uterine Hemorrhage