Cervicovaginal Ureaplasma and Mycoplasma hominis linked to preterm birth

Design

Systematic review and multivariate meta-analysis of observational studies

Population

156 studies of pregnant women with genital mycoplasma testing

Primary outcome

Preterm birth and other adverse pregnancy outcomes

Effect

U. parvum and preterm birth OR 1.63 (1.36 to 1.96); M. hominis aOR 1.75 (1.21 to 2.53)

This systematic review pooled 156 observational studies of genital mycoplasmas in pregnancy, published in AJOG in March 2026. Sensitivity analyses restricted to cervicovaginal samples, excluding amniotic fluid and placental specimens.

Cervicovaginal Ureaplasma parvum was associated with preterm birth (OR 1.63, 95% CI 1.36 to 1.96). Ureaplasma species were associated with low birthweight (OR 1.56, 1.33 to 1.83) and small for gestational age (OR 1.47, 1.19 to 1.80), with stronger associations for first-trimester detection. Mycoplasma hominis was associated with preterm birth (adjusted OR 1.75, 1.21 to 2.53) and low birthweight (OR 1.81, 1.51 to 2.16).

The authors are explicit that these associations do not support routine screening or treatment. These organisms are common, travel with other features of the vaginal microbiome, and no trial here shows that eradicating them changes outcomes. The practical value is in interpreting a positive result when it arrives, not in ordering the test.

• Do not add routine Ureaplasma or Mycoplasma hominis swabs to antenatal screening on the strength of this review.
• Read a positive cervicovaginal result as a marker of the wider vaginal microbiome, not an isolated pathogen.
• Keep Mycoplasma genitalium testing for symptomatic women and contacts, as current sexual health guidance advises.
• Where a woman already has a positive result and other preterm risk factors, it is reasonable to factor it into surveillance planning.

Why it matters

It shows the preterm link is not confined to organisms found inside the amniotic cavity.

Don't overread it

These are associations from observational data with residual confounding; no treatment benefit was shown.

The statistics, in plain English

An odds ratio of 1.63 means the odds of preterm birth were about 60% higher when Ureaplasma parvum was found. Every interval here stays above 1.0, so the associations are unlikely to be chance — but pooled observational studies cannot separate the organism from everything else that travels with it.

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