Amniotic fluid interleukin-6 and preterm delivery: a review

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.

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.

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

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.

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.