Objective: To ascertain whether the determination of amniotic fluid interleukin-6 (IL-6) concentrations would be a useful clinical test in the management of women with preterm contractions.
Setting: The labour and delivery unit and the Fetal Diagnostic Centre at the University of Utah.
Subjects: Pregnant women at various stages of gestation in the third trimester.
Design: Amniotic fluid samples were collected from women experiencing one of four clinical scenarios: 1. term pregnancy, not in labour with no evidence of intrauterine infection; 2. normal term labour with no evidence of infection; 3. preterm labour with no evidence of infection and undelivered within one week of sampling; and 4. preterm labour and delivered within seven days of sample collection. Amniotic fluid was obtained by amniocentesis or at the time of amniotomy or hysterotomy. IL-6 in each specimen was determined by a specific rapid ELISA.
Results: Amniotic fluid IL-6 levels, given as mean (SEM) in the four groups of women listed were: 1. term pregnancy, not in labour: 20.9 (7.2) pg/ml (n = 60); 2. normal term labour with no infection: 554 (90.7) pg/ml (n = 46); 3. preterm labour with no evidence of infection, undelivered: 47.0 (17.2) pg/ml (n = 35); and 4. preterm labour, delivered: 456.7 (101.7) pg/ml (n = 40). There was no significant difference in the means of amniotic fluid IL-6 for the term labour and preterm labour delivered groups. In general, amniotic fluid IL-6 levels during term labour increased with advancing cervical dilation. There was no correlation of cervical dilation and amniotic fluid IL-6 levels in women having preterm delivery. Receiver-operator curves revealed optimal IL-6 levels for discrimination of labour at term to be 50 pg/ml and for preterm delivery to be 200 pg/ml.
Conclusions: IL-6 can readily be detected in the amniotic fluid of most women who are in active labour, regardless of gestational age. Our data suggest that amniotic fluid IL-6 determinations may be clinically useful in the management of preterm labour.