Variables associated with meconium aspiration syndrome in labors with thick meconium

OBJECTIVE: To examine the possible maternal and fetal variables associated with meconium aspiration syndrome in labors with thick meconium. STUDY DESIGN: The fetal heart rate tracings, cord pH, Apgar scores and maternal risk factors were evaluated in singleton pregnancies with vertex presentation and thick meconium in labor. The study included 33 consecutive fetuses which developed a moderate or severe meconium aspiration syndrome and 104 consecutive fetuses which had a favorable outcome. RESULTS: Significant differences between fetuses with meconium aspiration syndrome and healthy fetuses were found in the following parameters: baseline FHR (154+/-17 vs. 136+/-10, P<0.0001), small accelerations/30 min (1.47+/-1.52 vs. 3.04+/-1.2, P<0.0001), large accelerations/30 min (1.46+/-1.96 vs. 3.5+/-2.31, P<0.0003), decelerations/30 min (4.9+/-3.9 vs. 2.4+/-2.1, P<0.0034), number of fetuses with reduced beat-to-beat variability (9/33 vs. 0/104, P<0.0001), cord pH (7.21+/-0.09 vs. 7.33+/-0.08, P<0.0013) and Apgar scores at 1 min (5+/-2 vs. 8+/-1, P<0.0001) and Apgar scores at 5 min (8+/-2 vs. 9.7+/-0.6, P<0.0001). Maternal risk factors were found in two of 33 sick infants and in 13 of 104 healthy infants. CONCLUSION: Thick meconium by itself is not associated with adverse fetal outcome. However, the incidence of meconium aspiration syndrome increases in cases of a non-reassuring FHR.