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

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.