The female genital tract microbiome may reflect female reproductive health and may be related to pregnancy outcomes. Disturbances in this microbiome may be associated with adverse reproductive outcomes. The investigators hypothesize that the endometrial and vaginal microbiome composition in women with a history of recurrent pregnancy loss are different, compared with those in normal fertile women.

The investigators want to describe the endometrial microbiome composition in normal fertile women and women with a history of recurrent pregnancy loss by analyzing mid-luteal phase vaginal swab and endometrial biopsy samples using 16S rRNA sequencing.

1. Recurrent pregnancy loss patients

   Inclusion Criteria:

   • 18-38 years old
   • Having a regular menstrual cycle, from 25 to 35 days
   • Having ≥ 2 recurrent pregnancy loss and
   • Couples with normal karyotype results
   • Having no condition causing pregnancy loss such as antiphospholipid syndrome, abnormal thyroid function.
   • Agree to participate in the study

   Exclusion Criteria:

   • Irregular menstrual cycle
   • Having uterine abnormalities (e.g., adenomyosis, intrauterine adhesions, unicornuate/ bicornuate/ arcuate uterus; unremoved hydrosalpinx, endometrial polyp, submucosal fibroid)
   • Using intrauterine device within the last 3 months
   • Using antibiotic/vaginal pessary/contraceptive pills within 2 weeks
   • Having sexual intercourse within 48 hours

2. Healthy control patients

Inclusion Criteria:

• 18-38 years old
• Having a regular menstrual cycle, from 25 to 35 days
• No history of pregnancy loss
• Having 1 or more live birth, with the youngest child ≥ 6 months old
• Agree to participate in the study

Exclusion Criteria:

• Irregular menstrual cycle
• Having uterine abnormalities (e.g., adenomyosis, intrauterine adhesions, unicornuate/ bicornuate/ arcuate uterus; unremoved hydrosalpinx, endometrial polyp, submucosal fibroid)
• Using intrauterine device within the last 3 months
• Using antibiotic/vaginal pessary/contraceptive pills within 2 weeks
• Having sexual intercourse within 48 hours

For RPL women: having ≥ 2 recurrent pregnancy loss. For NF women: having ≥ 1 live birth, with no history of pregnancy loss