Intrauterine infection and preterm delivery: Evidence for activation of the fetal hypothalamic-pituitary-adrenal axis

OBJECTIVE: We studied pregnant women in preterm labor with and without intrauterine infection to determine whether fetal hypothalamic-pituitary-adrenal axis activation occurs in the setting of infection-induced preterm parturition. STUDY DESIGN: Amniotic fluid collected by amniocentesis and maternal blood from patients in preterm labor with intact membranes at 24 to 34 weeks' gestation were analyzed by radioimmunoassay for the steroid hormones estrone, estradiol, progesterone, androstenedione, dehydroepiandrosterone, dehydroepiandrosterone sulfate, and cortisol. Amniotic fluid was also obtained for microbial culture and for interleukin 6 measurements by enzyme immunoassay. RESULTS: Patients with intrauterine infection (n = 11) had significantly higher amniotic fluid concentrations of dehydroepiandrosterone (539 +/- 79 pg/mL) and of cortisol (5.28 +/- 1.0 mu g/dL) than did patients with preterm labor and preterm delivery without infection (n = 11;273 +/- 82 pg/mL and 1.61 +/- 1.05 mu g/dL, respectively) or patients with preterm labor and subsequent term delivery (n = 11;202 +/- 79 pg/mL and 1.82 +/- 1.0 mu g/dL, respectively). Furthermore those patients who were delivered within 7 days after enrollment (who were also more likely to have intrauterine infection) had higher amniotic fluid concentrations than did those who were not delivered within 7 days of both estrone (586 +/- 101 pg/mL vs 314 +/- 98 pg/mL) and estradiol (238 +/- 44 pg/mL vs 91 +/- 43 pg/mL). CONCLUSION: Intrauterine infection was associated with increased fetal adrenal androgen and cortisol biosynthesis, and delivery within 7 days after the onset of preterm labor was associated with increased placental estrogen synthesis. These data are consistent with fetal hypothalamic-pituitary-adrenal axis activation in the setting of infection-associated preterm delivery.