The earlier the gestational age, the greater the intensity of the intra-amniotic inflammatory response in women with preterm premature rupture of membranes and amniotic fluid infection by Ureaplasma species

Abstract

Objectives To determine the relationship between the intensity of the intra-amniotic inflammatory response and the gestational age at the time of diagnosis in cases with preterm premature rupture of membranes (PROM) and intra-amniotic infection caused by Ureaplasma spp. Methods A retrospective cohort study was conducted which included 71 women with preterm PROM and a positive amniotic fluid culture with Ureaplasma spp. Women with mixed intra-amniotic infections were excluded. The study population was classified into three groups according to gestational age: group 1, <26 weeks (extreme preterm PROM, n = 17); group 2, 26.0-33.9 weeks (moderate preterm PROM, n = 39); group 3, 34.0-36.9 weeks (late preterm PROM, n = 15). The intensity of the intra-amniotic and maternal inflammatory response was compared among the three groups. The intensity of the intra-amniotic inflammatory response was assessed by the concentration of amniotic fluid matrix metalloproteinase-8 (MMP-8) and white blood cell (WBC) count. The maternal inflammatory response was assessed by the concentration of C-reactive protein (CRP) and WBC count in maternal blood at the time of amniocentesis. Results (1) The median values of amniotic fluid MMP-8 concentration and WBC count were the highest in the extreme preterm PROM group and the lowest in the late preterm PROM group (P < 0.001 and P = 0.01, respectively); (2) the intensity of the maternal inflammatory response measured by maternal blood WBC count and CRP concentration was not significantly associated with gestational age at the time of diagnosis. Conclusion The earlier the gestational age at the time of PROM, the higher the intensity of the intra-amniotic inflammatory response in women with preterm PROM and intra-amniotic infection caused by Ureaplasma spp.

Keywords: Ureaplasma; chorioamnionitis; intra-amniotic infection; intra-amniotic inflammation; matrix metalloproteinase-8; microbial invasion of amniotic cavity; prematurity; preterm labor; preterm premature rupture of membranes.

Figure 1.

Amniotic fluid matrix metalloproteinase-8 concentrations according to gestational age at amniocentesis (i.e., −25.9 weeks, 26.0–33.9 weeks, and 34.0–36.9 weeks) in women with intra-amniotic infection by Ureaplasma spp. (median: 714.6 ng/mL, interquartile range [IQR]: 165.8–2681.2 ng/mL vs. median: 157.7 ng/mL, IQR: 24.9–870.8 ng/mL vs. median: 24.0 ng/mL, IQR: 1.8–272.3 ng/mL; P=.002 by Kruskal-Wallis analysis).

Figure 2.

The frequency of intra-amniotic inflammation (defined as amniotic fluid matrix metalloproteinase-8 concentration > 23 ng/mL) according to the gestational age (P=0.002 by linear by linear association).