Prognostic Value of Change in Amniotic Fluid Color During Labor

Meconium staining of amniotic fluid (AF), seen in an estimated 7% to 22% of term pregnancies, has been viewed as a sign of fetal maturity. There is, however, some evidence that it may also reflect a response of the fetal gastrointestinal tract to acute or chronic hypoxia. This study was planned to determine the prevalence of altered AF color, its clinical significance, and whether it can predict perinatal outcomes. Changes in AF color were monitored in all singleton pregnancies during the years 1992-1999 that presented at 37-42 weeks, excluding stillbirths, congenital anomalies, and elective cesarean deliveries. Among 19,090 cases were 16,975 with clear AF at admission and at delivery; 973 with clear AF at admission light or thick meconium at delivery; and 156 with light meconium on admission and thick meconium at delivery. Changes in AF color during labor were more prevalent in nulliparous women. Gestations with a change in AF color during labor were associated with significantly higher rates of low 5-minute Apgar scores and of an umbilical artery pH less than 7.10. Using women with clear AF throughout as a baseline, acidosis was more frequent when there was a change in AF color during labor-especially from clear AF to meconium-and only the latter group had a greater chance of admission to neonatal intensive care. Meconium aspiration syndrome was more frequent in cases with light meconium at admission changing to thick meconium during labor. Cesarean deliveries were more numerous in cases with meconium at admission and no change during labor (relative risk [RR], 2.1; 95% confidence interval [CI], 1.6-2.6); in cases with a change from clear AF to meconium (RR, 4.2; 95% CI, 3.4-5.1); and in cases with a change from light to thick meconium (RR, 4.6; 95% CI, 3.0-7.2). The increased risk did not depend on whether labor was spontaneous or induced. These findings suggest that the color of AF be evaluated early in labor. New ways are needed to assess AF color accurately and noninvasively.