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El-Bastawissi, Amira Y. MBCHB, PhD; Williams, Michelle A. ScD; Riley, Donald E. PhD; Hitti, Jane MD, MPH; Krieger, John N. MD


Objective To evaluate the potential role of amniotic fluid (AF) interleukin (IL)-6 as a predictor of preterm delivery and to consider possible explanations for the proportion of women with elevated AF IL-6 who deliver preterm yet lack microbiologically detectable intra-amniotic infection.

Data Sources We searched the English language human literature in MEDLINE, 1966 through September 1999, using the keywords “labor/infant,” “premature,” “cytokines/interleukin-6,” and “AF.” We also examined abstracts from the 1999 meetings of the Society for Maternal-Fetal Medicine and the Society for Epidemiologic Research. We identified other studies by reviewing the reference lists of published articles.

Methods of Study Selection The MEDLINE search yielded 55 citations. We focused on studies that reported on the association between AF IL-6 and preterm delivery.

Tabulation, Integration, and Results There is consensus in the literature that elevated AF IL-6 is a stronger predictor of preterm delivery than intra-amniotic infection detected by either microbiologic culture or polymerase chain reaction (PCR). Among women with elevated AF IL-6, PCR could detect a higher proportion of intra-amniotic infection than culture. A number of women with elevated AF IL-6 (33–70%) deliver preterm and do not have evidence of intra-amniotic infection by either culture or PCR. Possible explanations for this observation are considered.

Conclusion Elevated AF IL-6 is strongly associated with preterm delivery and merits future consideration in clinical settings to predict preterm delivery and guide patient care. Development of improved polymerase chain reaction-based clinical methods to detect intra-amniotic infection is necessary to better understand the relationship between elevated AF IL-6, intra-amniotic infection, and preterm delivery.

Results from available literature suggest that elevated amniotic fluid interleukin-6 is a better predictor of preterm delivery than microbiologically detectable intra-amniotic infection.

Departments of Epidemiology, Urology, Pathobiology, and Obstetrics and Gynecology, University of Washington; and the Center for Perinatal Studies, Swedish Medical Center, Seattle, Washington.

Address reprint requests to: Amira Y. El-Bastawissi, PhD Swedish Medical Center Center for Perinatal Studies 747 Broadway Seattle, WA 98122-4307 E-mail:

This work was supported by grant R40 MC 00113 from the Maternal and Child Health Bureau (Title V, Social Security Act), Health Resources and Services Administration, Department of Health and Human Services.

Received September 20, 1999. Received in revised form January 18, 2000. Accepted February 10, 2000.

© 2000 The American College of Obstetricians and Gynecologists