Cultivable vaginal Lactobacillus is not associated with fecundability in Kenyan women attempting to conceive.
Level 3 - non-randomized controlled study
Prospective observational cohort study
PubMed 35058047 · doi:10.1016/j.fertnstert.2021.11.032
What was done
A prospective preconception cohort study was conducted in Nairobi and Mombasa, Kenya, among women attempting nonmedically assisted conception with ≤3 months of pre-enrollment attempt time. At up to six monthly visits, participants reported menstrual cycle timing and sexual behavior, underwent pregnancy testing, and provided vaginal swabs for Lactobacillus culture (primary) and Gram stain morphotypes (secondary). Associations between Lactobacillus presence at the cycle prior to pregnancy testing and fecundability (per-cycle probability of pregnancy) were estimated using proportional probabilities models to generate fecundability ratios (FRs), adjusted for age, frequency of condomless sex, and study site.
What was found
Among 458 women contributing 1,376 menstrual cycles, 65.3% (n = 299) had cultivable Lactobacillus, 47.4% (n = 217) had cultivable hydrogen peroxide–producing Lactobacillus, and 64.6% (n = 296) had Lactobacillus detected on Gram stain at enrollment. Cultivable Lactobacillus at the prior visit was not associated with fecundability in unadjusted analysis (FR 0.92, 95% CI 0.73–1.16) or adjusted analysis (adjusted FR 0.92, 95% CI 0.72–1.18). Lactobacillus detected on Gram stain was not statistically significantly associated with fecundability (adjusted FR 1.18, 95% CI 0.92–1.51).
Why it matters
This study shows that the presence of cultivable vaginal Lactobacillus alone does not enhance per-cycle conception rates in women attempting natural conception, suggesting that broad Lactobacillus presence without species-specific resolution is insufficient to predict fecundability.
Limits
The study relied on culture and Gram stain morphotyping rather than molecular sequencing, precluding species- or strain-level analysis. Observation was limited to a maximum of six monthly cycles per participant, and residual confounding from unmeasured co-infections or lifestyle factors cannot be ruled out.
Cited by
- contradicts A healthy, Lactobacillus-dominated vaginal microbiome without dysbiosis is associated with a shorter time to conceive, successful embryo implantation, and improved IVF success rates.