Impact of Thin and Thick Intrapartum Meconium-Stained Amniotic Fluid on Cesarean Delivery and Neonatal Outcomes in Low-Risk Pregnancies.

Objective: To evaluate whether thin and thick meconium-stained amniotic fluid are risk factors for increased rates of cesarean delivery, both for fetal and non-fetal distress indications, as well as for operative vaginal delivery. Methods: A retrospective cohort study was conducted on low-risk singleton pregnancies. They were divided into three groups for comparisons of outcomes: the control group (clear amniotic fluid), the thin meconium group, and the thick meconium group. Results: A total of 12,171 women met the inclusion criteria, comprising 10,341 with clear amniotic fluid and 1,730 (15.0%) with meconium-stained amniotic fluid, of which 1,159 (9.5%) had thin meconium and 671 (5.5%) had thick meconium. Most labor outcomes in the thin meconium group were comparable to those in the control group. However, in the thick meconium group, the overall rate of cesarean delivery, including those indicated for both fetal distress and non-fetal distress, as well as the rate of operative vaginal delivery, were significantly increased after adjustment for potential confounders, with adjusted odds ratios of 1.93, 2.25, 1.72, and 1.95, respectively. Additionally, the rate of low Apgar scores was significantly higher in the thick meconium group. Conclusion: Thick meconium-stained amniotic fluid was identified as a risk factor for an increased rate of cesarean delivery, both for fetal distress and non-fetal distress indications. The latter may be related to a lower threshold for decision-making, as physicians may fear potential fetal compromise, leading to unnecessary cesarean deliveries. Stricter criteria for cesarean section indications in cases of thick meconium should therefore be emphasized.