Incidence of Chorioamnionitis in Patients With Meconium-stained Amniotic Fluid

Objective: The goal of this study was to determine if meconium staining of the amniotic fluid (MSAF) is a marker for chorioamnionitis. Methods: In a retrospective, case-control investigation, we studied 100 patients with MSAF. Each patient was matched with a control who delivered during the same period but did not have MSAF. Subjects and controls were matched for age, parity, gestational age, mode of delivery, duration of rupture of membranes (ROM), length of internal monitoring, and number of examinations before and after ROM. The incidence of chorioamnionitis in controls and study patients was compared. The diagnosis of chorioamnionitis was based on clinical examination. Results: Thirteen of the 200 patients [6.5%, 95% confidence interval (CI), 2.5–10.5%] developed chorioamnionitis. Of the 100 women with MSAF, 10 (10%, 95% CI, 4–16) were infected compared with only 3 controls (3%, 95% CI, 0–6, P = 0.04). The odds ratio (OR) for this comparison was 3.3, and the 95% CI was 1.02–10.63. Conclusions: MSAF is associated with an increased frequency of chorioamnionitis. Several factors could explain this association. Infection may cause fetal stress, leading to the release of meconium. MSAF may enhance the growth of bacteria by providing a rich medium of essential nutrients or growth stimulants. MSAF also may impair the host immune system so that chemotaxis or phagocytosis is diminished, thus allowing accelerated growth of microorganisms.