Meconium-stained amniotic fluid is reported in 7 to 22 percent of term deliveries. Amnio-infusion is used to reduce meconium aspiration syndrome, a leading cause of neonatal morbidity and mortality. A Cochrane review of randomized trials suggests that amnioinfusion decreases the occurrence of this syndrome, but the trials used for this review had limitations, most notably size. To address this, Fraser and colleagues conducted a large, multicenter, randomized controlled trial to determine the efficacy of amnioinfusion for thick meconium amniotic fluid staining.

Enrollment criteria included active labor, gestation of 36 weeks or greater, ruptured membranes, thick meconium amniotic fluid staining, cervical dilation between 2 and 7 cm, and no clinical signs indicating urgent delivery. A total of 1,998 women were randomized to amnioinfusion or usual care, and 1,975 were eligible to participate in the final analysis of the study. Block randomization according to the presence or absence of variable decelerations on fetal monitoring occurred before treatment randomization. Oropharyngeal and nasal suctioning were performed after delivery of the fetal head. Because prophylactic pharyngeal suctioning and intubation and suctioning have not been shown to reduce meconium aspiration syndrome, these interventions were used only for infants in respiratory distress. The primary outcome measure for this trial was a composite of perinatal death, moderate to severe meconium aspiration syndrome, or both.

The average maternal age was 26 years, and most patients were term (53 percent) or postterm (41 percent); 55 percent were nulliparous. The composite outcome occurred in 44 infants (4.5 percent) in the amnioinfusion group and 35 infants (3.5 percent) in the control group. Moderate to severe meconium aspiration syndrome was diagnosed in 43 intervention infants (4.4 percent) and 31 control infants (3.1 percent). Five deaths occurred in each group. Mild respiratory distress occurred with equal frequency in both groups. Analysis showed no significant difference between the groups based on the intervention or according to the block randomization for variable decelerations. There also was no significant difference in neonatal respiratory interventions such as oxygen, bag ventilation, or intubation.

The authors conclude that amnioinfusion for thick meconium staining does not decrease the risk of meconium aspiration syndrome or perinatal death. They recommend against using it for these purposes.