ABSTRACT OBJECTIVE: The mechanism underlying cervical dilation in women with idiopathic cervical incompetence (ICI) is unknown. We investigated the potential roles of relaxin and subclinical intra-amniotic inflammation by quantitating amniotic fluid relaxin and interleukin-6(IL-6) concentrations in women with ICI.
STUDY DESIGN: Idiopathic CI was diagnosed when the cervical dilatation > 2cm between 15 and 27 weeks’ gestation associated with intact but bulging membranes and the absence of detectable uterine activity (n=40). Each woman underwent amniocentesis to facilitate the rescue cerclage. Forty-five additional women who underwent amniocentesis for chromosomal screening between 16 and 27 weeks’ gestation served as a control group. All control patients delivered chromosomally normal infants at > 37 weeks. IL-6 and relaxin were determined in all amniotic fluid samples by enzyme-linked immunosorbent assay.
RESULTS: Amniotic fluid IL-6 levels were significantly higher in women with ICI than control (CRL: 50.4 [19.4-97.4] pg/ml vs. CI: 5459.1 [1131.4-14425.7] pg/ml, p<0.001). In contrast to IL-6, relaxin levels did not differ between the 2 groups (CRL: 67.5 [35.1-153.5] pg/ml vs. ICI: 45.6 [30.1-75.5] pg/ml, p=0.061). There was a significant difference in IL-6 levels in women with shorter latencies (p<0.01 for all latency intervals examined: delivery within 24h, 3d, 7d, before 33 and 37 completed week gestation). Linear regression analysis using the latency interval from cerclage to delivery as the dependent and IL-6 as the independent variable revealed a significant inverse relationship (r= - 0.36, p=0.021 for linear data and r = -0.62, p<0.001 after log transformation of IL-6). There was no relationship on regression analysis between relaxin before (r=0.15, p=0.337) or after log transformation (r=0.269, p=0.093)) and latency interval.
CONCLUSION: Amniotic fluid IL-6 is significantly increased in patients with ICI suggesting subclinical inflammation may be a contributing factor to ICI. Further, an elevated IL-6 strongly predicts failure of the rescue cerclage. In contrast, relaxin, as reflected in the amniotic fluid does not appear contribute to ICI-induced cervical dilation.

OBJECTIVE: In patients with idiopathic cervical incompetence (CI), cervical dilation occurs without evidence of active labor. We investigated the potential role of intra-amniotic relaxin in the mechanism of idiopathic cervical dilation during midpregnancy.

STUDY DESIGN: Amniotic fluid relaxin levels were determined in patients with diagnosed idiopathic CI (cervical dilatation ≥ 2cm, intact bulging membranes, no active labor) between 15 and 27 weeks’ gestation (n=55). A group of patients having amniocentesis for chromosomal screening between 16 and 27 weeks’ gestation (n=55) served as controls. All control patients delivered chromosomally normal infants at ≥ 37 weeks. All patients received amniocentesis for measurement of amniotic fluid relaxin. In patients with CI, amniocentesis was performed prior to cervical cerclage. Relaxin levels were determined by enzyme-linked immunosorbent assay and statistical analysis performed with the Mann-Whitney U test.
RESULTS: The median amniotic fluid relaxin concentrations of the patients with idiopathic CI not show differ significantly from control cases (median 42.6 [range 7.1 - 783.2] vs. 78.5 [range, 5.0 - 3000.0] ng/ml; p>.05). CONCLUSION: There is no significant increase in amniotic fluid relaxin levels in patients with idiopathic CI. These results suggest that relaxin does not contribute to the mechanism of CI-induced cervical dilation.

Am J Obstet Gynecol, 2002; 187: s95

INFLAMMATORY MECHANISM FOR IDIOPATHIC CERVICAL INCOMTETENCE: ELEVATED AMNIOTIC FLUID INTERLEUKIN-6 (IL-6) AND MATRIX METALLOPROTEINASE-8 (MMP-8)
Keun-young Lee, M.D., Hyun-ah Jun M.D., Hong-bae Kim,M.D., Sung-won Kang, M.D, Department of Obstetrics and Gynecology, Hallym University, Seoul, Korea
OBJECTIVE: The mechanism of cervical dilation in patients with idiopathic cervical incompetence (CI) is unknown. We evaluated the role of subclinical intra-amniotic inflammation by assessing amniotic fluid IL-6 and MMP-8 levels in patients with CI, in the absence of labor.
STUDY DESIGN: Patients with diagnosed idiopathic CI (cervical dilatation ≥ 2cm, intact bulging membranes, no active labor) between 15 and 32 weeks’ gestation (n=55) received amniocentesis for measurement of amniotic fluid IL-6 and MMP-8 levels. Amniocentesis was performed prior to cervical cerclage. Comparison was made with control patients having amniocentesis for chromosomal screening between 16 and 31 weeks’ gestation (n=55). All control patients delivered chromosomally normal infants at ≥ 37 weeks. IL-6 and MMP-8 levels were determined by enzyme-linked immunosorbent assays. Analysis was performed with the Mann-Whitney U test.
RESULTS: The median amniotic fluid IL-6 and MMP-8 concentrations of the patients with idiopathic CI were significantly higher than those of the control cases (IL-6 median 5,641 [range 27 ? 89,886] vs 50 [range 7-1,638] pg/ml, respectively; p<.001), (MMP-8 median 45.4 [range 0.3-270.3] vs 0.75 [range, 0.037-18.8] ng/ml, respectively; p<.001)
CONCLUSION: Amniotic fluid IL-6 and MMP-8 levels are significantly increased in patients with idiopathic CI, despite the absence of labor. These results suggest that subclinical inflammation may be an etiological factor contributing to idiopathic cervical incompetence.

Am J Obstet Gynecol, 2002; 187: s95