Cultivable vaginal Lactobacillus is not associated with fecundability in Kenyan women attempting to conceive

Fertil Steril. 2022 Mar;117(3):603-611. doi: 10.1016/j.fertnstert.2021.11.032. Epub 2022 Jan 17.


Objective: To examine the association between cultivable vaginal Lactobacillus and fecundability in Kenyan women attempting nonmedically assisted conception.

Design: Prospective preconception cohort.

Setting: Nairobi and Mombasa, Kenya.

Patient(s): Women trying to conceive who reported ≤3 months of pre-enrollment conception attempt time.

Intervention(s): Cultivable Lactobacillus (primary), Lactobacillus morphotypes on Gram stain (secondary).

Main outcome measure(s): Participants reported the first day of their last menstrual period and recent sexual behavior, underwent pregnancy testing, and provided vaginal specimen samples for Lactobacillus culture and Gram stain at ≤6 monthly preconception visits. The outcome was fecundability-the per-menstrual cycle probability of pregnancy. Associations between cultivable Lactobacillus and Lactobacillus morphotypes on Gram stain at the visit before each pregnancy test and fecundability were estimated using proportional probabilities models to generate fecundability ratios (FRs).

Result(s): A total of 458 women contributed 1,376 menstrual cycles. At enrollment, 65.3% (n = 299) of participants had cultivable Lactobacillus, 47.4% (n = 217) had cultivable hydrogen peroxide producing Lactobacillus, and 64.6% (n = 296) had Lactobacillus detected on Gram stain. In unadjusted analysis, there was no association between cultivable Lactobacillus at the prior visit and fecundability (FR, 0.92; 95% CI, 0.73-1.16); results were similar after adjustment for age, frequency of condomless sex, and study site (adjusted FR, 0.92; 95% CI, 0.72-1.18). Lactobacillus on Gram stain at the visit prior was associated with modestly higher fecundability (adjusted FR, 1.18; 95% CI, 0.92-1.51).

Conclusion(s): Cultivable Lactobacillus was not associated with fecundability, although Lactobacillus morphotypes detected on Gram stain were somewhat associated with increased fecundability. The relationship between vaginal Lactobacillus and fecundity may be species-specific.

Keywords: Lactobacillus; fecundability; fertility; preconception; vaginal microbiota.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • Cohort Studies
  • Female
  • Fertility / physiology*
  • Fertilization / physiology*
  • Humans
  • Kenya / epidemiology
  • Lactobacillus / isolation & purification*
  • Middle Aged
  • Preconception Care / methods*
  • Preconception Care / trends
  • Pregnancy
  • Prospective Studies
  • Time-to-Pregnancy / physiology*
  • Vagina / microbiology*
  • Young Adult