Amniotic fluid interleukin-18 at mid-trimester genetic amniocentesis: relationship to intraamniotic microbial invasion and preterm delivery

Abstract

Objective: To determine the value of amniotic fluid interleukin-18 (AF IL-18) in the diagnosis of microbial invasion of the amniotic cavity and prediction of preterm delivery (PTD).

Design: Analysis of the results of AF collected prospectively following genetic amniocentesis between February 2006 and September 2007.

Setting: A tertiary referral centre for fetal medicine.

Methods: Following amniocentesis, a sample of amniotic fluid was transferred to the laboratory for aerobic and anaerobic bacterial cultures, Ureaplasma urealyticum culture and IL-18 assays. All women who delivered preterm (<37 weeks of gestation) formed the study group. The control group consisted of the two subsequent women who also underwent amniocentesis during the same time period and delivered a normal neonate at term, matched for maternal age, parity and indication for amniocentesis.

Main outcome measures: The relationship between AF IL-18 levels and the risk of both microbial invasion of the amniotic cavity and PTD.

Results: Forty-eight women who delivered preterm (<37 weeks) were matched with 96 controls. The preterm delivery group had significantly higher concentrations of IL-18 (median=609 pg/ml, interquartile range: 445.7-782.7) compared to controls (median=322.1 pg/ml, interquartile range: 277.7-414.4), (P<0.001). IL-18 level was also significantly higher (P<0.001) in cases with positive amniotic fluid cultures (median=697.7, interquartile range: 609.0-847.2) compared to those with negative ones (median=330.9 pg/ml, interquartile range: 235.2-440.8).

Conclusions: Elevated mid-trimester concentrations of AF IL-18 can identify women at risk for intraamniotic infection and spontaneous PTD.