Pregnant woman surrounded by glowing bacterial forms (Ureaplasma and Mycoplasma) within a womb-like space, intertwined with DNA strands, with faint antibiotic molecules hovering around.

Unmasking the Silent Threat: How Antibiotics Impact Preterm Birth Risk in Women with Ureaplasma/Mycoplasma Colonization

Jordan Keane in Health & Wellness June 2025 • 4 min read.

"A Deep Dive into a Randomized Trial and What It Means for Expectant Mothers"

Preterm birth, defined as delivery before 37 weeks of gestation, remains a significant global health concern, affecting approximately 5.5% to 12% of births in high-income countries. It's a leading cause of infant morbidity and mortality, with the most severe consequences often observed in babies born before 30 weeks. Understanding the factors that contribute to preterm birth is essential for developing effective prevention strategies.

One area of ongoing research focuses on the role of infection, particularly the presence of certain bacteria in the amniotic fluid. Some studies have suggested a link between the colonization of the amniotic fluid with bacteria like Ureaplasma spp. and Mycoplasma hominis and an increased risk of preterm birth. These bacteria, commonly found in the vaginal flora, may ascend into the uterus, triggering an inflammatory response that leads to premature labor and delivery.

To investigate this potential link, a team of researchers in France conducted a randomized, double-blind, placebo-controlled trial to assess whether antibiotics could prevent preterm birth in women with amniotic fluid colonization by Ureaplasma and/or Mycoplasma spp. during the second trimester. This article delves into the study's methodology, findings, and implications for prenatal care.

Antibiotics and Preterm Birth: The Key Findings

Pregnant woman surrounded by glowing bacterial forms (Ureaplasma and Mycoplasma) within a womb-like space, intertwined with DNA strands, with faint antibiotic molecules hovering around.

The study, published in PLOS ONE, involved 1043 women who underwent amniotic fluid screening as part of routine Down syndrome screening between 16 and 20 weeks of gestation. Amniotic fluid samples were tested for the presence of Ureaplasma urealyticum, Ureaplasma parvum, Mycoplasma hominis, and Mycoplasma genitalium using PCR (polymerase chain reaction) techniques.

Women who tested positive for Ureaplasma and/or Mycoplasma spp. were then randomized to receive either josamycin, an antibiotic, or a placebo for 10 days. The primary outcome of the study was delivery before 37 weeks of gestation. Secondary outcomes included delivery before specific gestational ages (22, 28, and 32 weeks), birth weight, and selected neonatal complications.

Low Colonization Rate: The study revealed a surprisingly low rate of amniotic fluid colonization by Ureaplasma and/or Mycoplasma spp., only 3% of the women tested positive.
Premature Trial Termination: Due to the low colonization rate, the trial was stopped prematurely.
No Significant Difference: Among the small group of women who were randomized, there was no significant difference in preterm delivery rates between the josamycin and placebo groups.
No Association: In comparing all PCR-positive and -negative women, PCR positivity was not associated with any adverse pregnancy or neonatal outcome.

Interestingly, further analysis using 16S rDNA PCR revealed other bacterial presence, for Sphingomonas sanxanigenes, Acinetobacter baumannii, Bacillus niabensis, Acinetobacter johnsonii and Streptococcus oralis but these were deemed as probable contaminants with no preterm deliveries. These findings suggest that maternal amniotic-fluid colonization by Ureaplasma and/or Mycoplasma spp. at 16–20 weeks in asymptomatic women is rare and not associated with adverse pregnancy outcomes.

What This Means for Prenatal Care

While this study's findings may seem discouraging, they provide valuable insights for prenatal care. The low rate of amniotic fluid colonization suggests that routine screening for Ureaplasma and/or Mycoplasma spp. in asymptomatic women may not be warranted. More research is needed to identify specific risk factors for amniotic fluid colonization and to determine the most effective strategies for preventing preterm birth in women with these infections. As always, discuss any concerns with your healthcare provider to develop a personalized care plan.

About this Article -

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This article is based on research published under:

DOI-LINK: 10.1371/journal.pone.0206290, Alternate LINK

Title: Antibiotics For Amniotic-Fluid Colonization By Ureaplasma And/Or Mycoplasma Spp. To Prevent Preterm Birth: A Randomized Trial

Subject: Multidisciplinary

Journal: PLOS ONE

Publisher: Public Library of Science (PLoS)

Authors: Gilles Kayem, Alexandra Doloy, Thomas Schmitz, Yvon Chitrit, Philippe Bouhanna, Bruno Carbonne, Jean Marie Jouannic, Laurent Mandelbrot, Alexandra Benachi, Elie Azria, Francoise Maillard, Florence Fenollar, Claire Poyart, Cécile Bebear, François Goffinet

Published: 2018-11-07

Everything You Need To Know

What were the key findings of the study on antibiotics and preterm birth related to Ureaplasma and Mycoplasma?

The study found a surprisingly low rate of amniotic fluid colonization by Ureaplasma and/or Mycoplasma spp., specifically only 3% of the women tested positive. In the small group of women randomized, there was no significant difference in preterm delivery rates between the josamycin and placebo groups. Furthermore, when comparing all PCR-positive and -negative women, PCR positivity was not associated with any adverse pregnancy or neonatal outcome. Although other bacterial presence was detected using 16S rDNA PCR for Sphingomonas sanxanigenes, Acinetobacter baumannii, Bacillus niabensis, Acinetobacter johnsonii and Streptococcus oralis, these were dismissed as probable contaminants with no preterm deliveries.

How was the study designed to investigate the link between Ureaplasma/Mycoplasma colonization and preterm birth, and what bacteria types were specifically tested?

The study involved 1043 women who underwent amniotic fluid screening as part of routine Down syndrome screening between 16 and 20 weeks of gestation. Amniotic fluid samples were tested for the presence of Ureaplasma urealyticum, Ureaplasma parvum, Mycoplasma hominis, and Mycoplasma genitalium using PCR (polymerase chain reaction) techniques. Women who tested positive for Ureaplasma and/or Mycoplasma spp. were then randomized to receive either josamycin, an antibiotic, or a placebo for 10 days. The primary outcome was delivery before 37 weeks of gestation.

Why is preterm birth a significant health concern, and what role might bacteria like Ureaplasma and Mycoplasma play in its occurrence?

Preterm birth is defined as delivery before 37 weeks of gestation. It is a significant global health concern, affecting approximately 5.5% to 12% of births in high-income countries. Preterm birth is a leading cause of infant morbidity and mortality, with the most severe consequences often observed in babies born before 30 weeks. This is why understanding contributing factors, like Ureaplasma spp. and Mycoplasma hominis colonization, is essential for developing effective prevention strategies.

Why was the randomized trial terminated prematurely, and what other bacterial presence was found during the study?

The trial was stopped prematurely due to the low rate of amniotic fluid colonization by Ureaplasma and/or Mycoplasma spp. Since only 3% of the women tested positive, the researchers did not have a large enough sample size to draw statistically significant conclusions about the effectiveness of josamycin in preventing preterm birth. Although further analysis found Sphingomonas sanxanigenes, Acinetobacter baumannii, Bacillus niabensis, Acinetobacter johnsonii and Streptococcus oralis these were considered contaminants.

What does the study imply for prenatal care and the routine screening of Ureaplasma and/or Mycoplasma spp. in asymptomatic women, and what further research is needed?

The study suggests that routine screening for Ureaplasma and/or Mycoplasma spp. in asymptomatic women may not be warranted, given the low rate of amniotic fluid colonization observed. However, it's important to identify specific risk factors for amniotic fluid colonization. Further research is needed to determine the most effective strategies for preventing preterm birth in women with these infections. Discuss any concerns with your healthcare provider to develop a personalized care plan. The study also implies the need to explore other potential causes and preventative measures for preterm birth.