Meconium-induced vasocontraction: a potential cause of cerebral and other fetal hypoperfusion and of poor pregnancy outcome.

Chronically meconium-stained fetuses may ultimately suffer cerebral palsy and other devastation. The mechanism is unknown. Innocuous pregnancy complications may cause some fetuses to discharge meconium, which may become hazardous, independently of aspiration. We herein report previously undescribed, meconium-induced umbilical and placental vascular necrosis. To investigate whether meconium causes vasocontraction, we tested umbilical vein tissue with an isometric transducer connected to a polygraph. The specimens were suspended in a 30-mL organ bath with Krebs solution (pH, 7.4; temperature, 37 degrees C; under aeration with 95% O2 and 5% CO2). We exposed the tissue to meconium and compared meconium-induced vasocontraction with that induced by Krebs solution and 10(-5) molar serotonin. Meconium maximally produced 62.9% of serotonin-induced vasocontraction. Krebs solution and boiled meconium did not produce vasocontraction. We hypothesize that meconium may cause placental and umbilical cord vasocontraction, cerebral and other fetal hypoperfusion, and major poor outcome.