Microorganisms such as bacteria live naturally on and in the bodies and are of great importance for our health. In the female body, almost 10% of all microorganisms live in the reproductive organs and especially in the vagina. Healthy bacteria in the vagina can defend against harmful bacteria and infections. However, it occasionally happens that the balance between healthy and harmful bacteria is disturbed, and it is believed that this could potentially harm pregnancy. However, there is not much evidence to prove a connection between an imbalance in bacteria and having an unsuccessful pregnancy.

For this reason, the goal of our study is to determine if women with certain vaginal bacteria are more likely to experience pregnancy failures. If the investigators find this to be true, patients undergoing fertility treatment might be recommended regular tests in the future. If an imbalance in bacteria is found, doctors could provide treatment to restore a healthy vaginal environment, potentially improving the chances of a successful pregnancy.

Inclusion Criteria:

• ART patients undergoing the transfer of a euploid embryo

Exclusion Criteria:

• Patients with a body mass index (BMI) ≥35

  • Patients with uncorrected uterine malformations
  • Patients with a unicornuate uterus
  • Patients with a bicornuate uterus
  • Patients with any type of submucosal myoma
  • Patients with an intramural myoma if ≥4 cm
  • Patients with severe adenomyosis (>50% of the uterine corpus affected as defined by the MUSA criteria [19])
  • Patients undergoing transfer of an embryo with a morphology score <4BC (according to the Gardner & Schoolcraft scoring system [18])
  • Patients undergoing transfer of a day-7 embryo
  • Patients who took antibiotics in the month prior to the embryo transfer (excluding antibiotics given following oocyte retrieval)

Eligible study participants are female ART patients scheduled for a frozen euploid embryo transfer