Meconium, oligohydramnios in postterm pregnancies risky. (Large Retrospective Study).

Los ANGELES -- The presence of thick meconium staining in low-risk postterm pregnancies was a better predictor of poor perinatal outcome than was oligohydramnios in a retrospective study of 3,050 pregnancies.

When the conditions are present together, thick meconium staining and oligohydramnios increased risk even more than did either alone, Dr. Alessandro Ghidini said in a poster presentation at the annual meeting of the Society for Gynecologic Investigation.

The results highlight the importance of assessing amniotic fluid color in monitoring postterm pregnancies, especially when oligohydramnios is present, said Dr. Ghidini of Georgetown University Hospital, Washington, D.C.

The retrospective study included low-risk postterm singleton pregnancies delivered within a 3-year period, 306 of which had oligohydramnios and 253 of which had heavy or thick meconium-stained fluid when membranes ruptured. (See chart.)

Low-birth-weight babies were more common in pregnancies with oligohydramnios than meconium staining (13% vs. 9%).

However, meconium staining was associated with an increased risk for acidemia at birth (4% vs. 0%) or low 5-minute Apgar scores (4% vs. 0.7%).

The combination of oligohydramnios and thick meconium staining increased the risks of low birth weight more than did either condition alone, a pathologic cardiotocogram during labor, or a C-section delivery for fetal distress.