Mid-trimester microbial invasion of the amniotic cavity and the risk of preterm birth

Abstract

Objective

To evaluate the rate of mid-trimester microbial invasion of the amniotic cavity (MIAC) in asymptomatic women and its association with preterm birth.

Study design

This is a prospective cohort study of asymptomatic women undergoing mid-trimester amniocentesis for genetic testing between 14 and 24 weeks of gestation. For each participant, a sample of amniotic fluid was incubated in an aerobic and anaerobic facultative culture media and another sample was tested for the presence of specific Mycoplasma species (Ureaplasma urealyticum, Ureaplasma parvum, and Mycoplasma hominis) using quantitative-PCR. Results were not revealed to the participants or their health care providers. All participants were followed until delivery. MIAC was defined by a positive culture or a positive PCR for Mycoplasma species. The primary outcome was a spontaneous preterm birth or preterm premature rupture of membranes before 35 weeks of gestation.

Results

We included 812 women at a median gestational age of 16 5/7 (interquartile: 15 6/7–17 4/7) weeks. Twenty-six (3.2%) had a spontaneous delivery before 35 weeks. We observed no case of positive PCR for Mycoplasma species and 4 (0.5%) cases of positive culture that were all considered to be skin contaminants. None of those four cases was associated with preterm birth. Nulliparity, low family income and history of preterm birth were associated with spontaneous delivery before 35 weeks.

Conclusion

We found no case of mid-trimester MIAC using a combination of culture and Mycoplasma-specific PCR techniques in a large cohort of low-risk asymptomatic pregnant women. We estimate that mid-trimester MIAC is rare in low-risk population but more sensitive and broad-range microbiologic techniques, such as 16S DNA detection by PCR, could be further evaluated.

Keywords:

• Amniotic fluid
• preterm birth
• pregnancy
• MIAC
• amniocentesis
• intraamniotic infection
• chorioamnionitis
• microbiology

Acknowledgments

We thank the members of the Department of Obstetrics & Gynecology and the Department of Genetics of the CHU de Québec – Université Laval, and of the CHU Ste-Justine for their collaboration in this study. The authors would also like to thank Josée Mailhot, Francine Dufour and Guylaine Aubé for their help in enrolling participants and collecting data for this study along with their dedicated care of each participant.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This research was supported by the Fonds de la Recherche en Santé du Québec [FRSQ, 14233] and the Jeanne et Jean-Louis Lévesque Perinatal research Chair at Université Laval. Dr Paul Guerby holds a postdoctoral Award [280207] from the FRQS and INSERM (Institut National de la Santé et de la Recherche Médicale).