Second trimester placenta previa. An apparently normal placentation.

Placental positions in 214 patients scheduled for genetic amniocentesis were reviewed. Forty-five percent were found to have ultrasound findings of a low-lying placenta or partial or total placenta previa. At term, none of these patients required intervention for bleeding or placenta previa. Parity of 4 or more, but not age, correlated with an increased incidence of partial or total placenta previa, but not with a low-lying placenta. Low-lying placenta or placenta previa may be a normal variant in early pregnancy, suggesting that failure of the placenta to relinquish this position can result in an abnormally implanted placenta at term.