Obstetric implications of low-lying placentas diagnosed in the second trimester.

OBJECTIVES

To determine the obstetrical outcome of pregnancies initially complicated by a low-lying placenta in the second trimester.

METHODS

We reviewed the obstetric outcome of all women with singleton deliveries from 1 January 1997 to 31 March 1999 and compared the 703 women with low-lying placentas (placentas in the lower uterine segment) with the 6938 women with placentas that were normally situated in the upper uterine segment at 16-22 weeks' gestation.

RESULTS

Pregnancies complicated by a low-lying placenta in the second trimester were not associated with antepartum hemorrhage, preterm births, preterm prelabor rupture of membranes, pregnancy-induced hypertension, fetal growth restriction or cesarean births. However, they had a higher incidence of postpartum hemorrhage (odds ratio 1.768, 95% confidence interval 1.137, 2.748) than women with a normally situated placenta in the second trimester.

CONCLUSIONS

Pregnant women with low-lying placentas in the second trimester have a higher incidence of postpartum hemorrhage and hence, it would be prudent to carefully manage the third stage of labor in these women.