Sterile and microbial-associated intra-amniotic inflammation in preterm prelabor rupture of membranes

Abstract

Objective: The objectives of this study were to: (1) determine the amniotic fluid (AF) microbiology of patients with preterm prelabor rupture of membranes (PROM); and (2) examine the relationship between intra-amniotic inflammation with and without microorganisms (sterile inflammation) and adverse pregnancy outcomes in patients with preterm PROM.

Methods: AF samples obtained from 59 women with preterm PROM were analyzed using cultivation techniques (for aerobic and anaerobic bacteria as well as genital mycoplasmas) and with broad-range polymerase chain reaction coupled with electrospray ionization mass spectrometry (PCR/ESI-MS). AF concentration of interleukin-6 (IL-6) was determined using ELISA. Results of both tests were correlated with AF IL-6 concentrations and the occurrence of adverse obstetrical/perinatal outcomes.

Results: (1) PCR/ESI-MS, AF culture, and the combination of these two tests each identified microorganisms in 36% (21/59), 24% (14/59) and 41% (24/59) of women with preterm PROM, respectively; (2) the most frequent microorganisms found in the amniotic cavity were Sneathia species and Ureaplasma urealyticum; (3) the frequency of microbial-associated and sterile intra-amniotic inflammation was overall similar [ 29% (17/59)]: however, the prevalence of each differed according to the gestational age when PROM occurred; (4) the earlier the gestational age at preterm PROM, the higher the frequency of both microbial-associated and sterile intra-amniotic inflammation; (5) the intensity of the intra-amniotic inflammatory response against microorganisms is stronger when preterm PROM occurs early in pregnancy; and (6) the frequency of acute placental inflammation (histologic chorioamnionitis and/or funisitis) was significantly higher in patients with microbial-associated intra-amniotic inflammation than in those without intra-amniotic inflammation [93.3% (14/15) versus 38% (6/16); p = 0.001].

Conclusions: (1) The frequency of microorganisms in preterm PROM is 40% using both cultivation techniques and PCR/ESI-MS; (2) PCR/ESI-MS identified microorganisms in the AF of 50% more women with preterm PROM than AF culture; and (3) sterile intra-amniotic inflammation was present in 29% of these patients, and it was as or more common than microbial-associated intra-amniotic inflammation among those presenting after, but not before, 24 weeks of gestation.

Keywords: Infection; Sneathia sp.; polymerase chain reaction with electrospray ionization mass spectrometry; pregnancy; prematurity; preterm delivery.

Figure 1

Bacteria and viruses detected in amniotic fluid of patients with preterm prelabor rupture of membranes standard cultivation techniques vs. PCR/ESI-MS. Amniotic fluid culture includes routine cultivation techniques for bacteria (aerobes, anaerobes, and genital mycoplasmas). PCR/ESI-MS refers to broad range polymerase chain reaction (PCR) and electrospray-ionization mass spectrometry (ESI-MS).

Figure 2

Prevalence of microbial associated and sterile intra-amniotic inflammation in patients with preterm prelabor premature of membranes according to the gestational age at diagnosis. The earlier the gestational age the rupture of the membranes occurs, the higher the frequency of both microbial-associated and sterile intra-amniotic inflammation.

Figure 3

Amniotic fluid concentrations of interleukin 6 in patients with a positive AF culture or PCR/ESI-MS according to the gestational age in which the rupture of the membranes occurred. Patients who presented with preterm PROM <25 weeks of gestation with a positive AF culture or PCR/ESI-MS had a significantly higher AF IL-6 concentrations than those who presented with a positive AF culture or PCR/ESI-MS between 25 and <33 weeks of gestation.