Preterm prelabor rupture of membranes without microbial invasion of the amniotic cavity and intra-amniotic inflammation: a heterogeneous group with differences in adverse outcomes

Abstract

Objective

The absence of microbial invasion of the amniotic cavity and intra-amniotic inflammation at the time of hospital admission is the most common condition associated with preterm prelabor rupture of membranes (PPROM). Although the intensity of intra-amniotic inflammatory response does not exceed the threshold for the diagnosis of intra-amniotic inflammation in this subgroup of PPROM, whether there could be differences in outcomes concerning the intensity of intra-amniotic inflammatory response remains unclear. Therefore, the main aims of this study on PPROM without microbial invasion of the amniotic cavity and intra-amniotic inflammation were (i) to characterize the association between the intensity of intra-amniotic inflammatory response, measured according to amniotic fluid interleukin (IL)-6 concentrations, and the presence of acute histological chorioamnionitis and acute inflammation in the amnion; (ii) to characterize the association between the intensity of intra-amniotic inflammatory response and fetal inflammatory response, and (iii) to describe the short-term morbidity of infants based on the intensity of intra-amniotic inflammatory response.

Methods

This retrospective study included 131 women with singleton pregnancies with PPROM without microbial invasion of the amniotic cavity and intra-amniotic inflammation between gestational ages of 24 + 0 and 36 + 6 weeks and who had delivered within 72 h of membrane rupture. Microbial invasion of the amniotic cavity was assessed based on a combination of cultivation and non-cultivation methods. Intra-amniotic inflammation was characterized based on the amniotic fluid IL-6 concentration. In addition, a histopathological assessment of the placenta was performed. Fetal inflammatory response syndrome was characterized according to IL-6 concentration in the umbilical cord blood of >11 pg/mL. Based on the quartiles of IL-6 concentrations in the amniotic fluid, these women were divided into four subgroups (from the lowest to the highest IL-6 concentrations).

Results

IL-6 concentrations in amniotic fluid were higher in women with acute histological chorioamnionitis (median: 819 pg/mL vs. 520 pg/mL; p = .003) and with acute inflammation of the amnion (median: 1116 pg/mL vs. 533 pg/mL; p = .0002) than in women without these complications. The rates of acute histological chorioamnionitis and acute inflammation of the amnion were the highest in the subgroup with IL-6 concentrations above the 75th percentile in amniotic fluid (chorioamnionitis, p = .02; amnion, p = .0002). No differences in IL-6 concentrations in amniotic fluid were identified between women with and without a fetal inflammatory response syndrome (p = .40). The rate of fetal inflammatory response syndrome did not vary among the amniotic fluid IL-6 quartile subgroups of women. Moreover, no differences were noted in short-term neonatal outcomes among the amniotic fluid IL-6 quartile subgroups.

Conclusion

A higher intensity of the intra-amniotic inflammatory response, measured by amniotic fluid IL-6 concentrations, is associated with a higher rate of acute inflammatory lesions in the placenta in the subset of PPROM pregnancies without microbial invasion of the amniotic cavity and intra-amniotic inflammation.

Keywords:

• Amniotic fluid
• amnion

Disclosure statement

The authors report that they have no conflicts of interest. The authors alone are responsible for the contents of the paper.

Additional information

Funding

This work was supported by the Faculty Hospital in Hradec Kralove (a long-term organization development plan) and Charles University, Faculty of Medicine in Hradec Kralove, Czech Republic, project PROGRES Q40/10.