Treatment of Mycoplasma hominis in Pregnant Women
For confirmed genital Mycoplasma hominis infection in pregnancy, clindamycin 300 mg orally twice daily for 7 days is the safest and most effective empiric regimen, as M. hominis is intrinsically resistant to macrolides including azithromycin. 1
Critical Distinction: M. hominis vs M. genitalium
A common and dangerous pitfall is confusing Mycoplasma hominis with Mycoplasma genitalium—these require completely different antibiotics:
- M. hominis is intrinsically resistant to all macrolides (azithromycin, erythromycin) due to lack of the 50S ribosomal binding site 1
- M. genitalium responds to azithromycin but not to clindamycin 2, 3
- The provided guidelines for azithromycin treatment 4, 2 specifically address M. genitalium or Chlamydia trachomatis, NOT M. hominis
Recommended Treatment Regimen for M. hominis
First-line therapy:
- Clindamycin 300 mg orally twice daily for 7 days 1
This regimen is:
- Safe in pregnancy (no teratogenic concerns) 1
- Effective against M. hominis specifically 1
- Well-tolerated with good compliance 1
Contraindicated Medications in Pregnancy
Absolutely avoid these antibiotics:
- Doxycycline - teratogenic potential, explicitly contraindicated 4, 2
- Fluoroquinolones (moxifloxacin, ofloxacin, levofloxacin) - fetal toxicity risk 4, 2, 5
- Tetracyclines - contraindicated throughout pregnancy 4, 6
Ineffective for M. hominis (do not use):
- Azithromycin - intrinsically resistant 1
- Erythromycin - intrinsically resistant 1
- All macrolides - intrinsically resistant 1
Alternative Considerations
Metronidazole may have activity against M. hominis, though clindamycin remains preferred:
- Metronidazole 250 mg orally three times daily for 7 days is safe in pregnancy 1
- Historical concerns about teratogenicity have not been confirmed in humans 1, 6
- Multiple studies show no consistent teratogenic or mutagenic effects 1
Clinical Management Pearls
Partner treatment:
- Sexual partners should be evaluated and treated empirically 4
- Abstain from intercourse until both partners complete treatment (7 days) 4
Follow-up:
- Consider test of cure 3 weeks after treatment completion 4
- Rescreen several months later given high reinfection rates in some populations 4
Pregnancy-specific concerns:
- M. hominis has been associated with adverse pregnancy outcomes including preterm birth, PPROM, and spontaneous abortion 7
- Systemic (oral) therapy is preferred over topical to treat possible subclinical upper genital tract infection 1
Emerging Resistance Concerns
Recent data shows increasing antibiotic resistance in genital mycoplasmas during pregnancy:
- 9.87% of pregnant women with mycoplasma infections had azithromycin-resistant strains (though this primarily affects M. genitalium and Ureaplasma, not M. hominis which is already intrinsically resistant) 7
- Azithromycin-resistant infections significantly increased adverse pregnancy outcomes 7
- This underscores the importance of using the correct antibiotic (clindamycin for M. hominis) from the outset 1