The purpose of this study is to determine whether preovulatory uterine flushing with physiological saline is effective in the treatment of unexplained infertility.

In vitro fertilisation is the only current reasonable treatment for unexplained infertility. Uterine flushing, associated with a five-fold increase in pregnancy when performed preovulatory, has been proposed as a new alternative. This treatment could flush out debris or alter inflammatory factors preventing fertilisation and implantation. The objective of this study is to assess the efficacy of pre-ovulatory uterine flushing with physiological saline for the treatment of unexplained infertility. This study is a randomised controlled trial based on consecutive women aged between 18 and 37 years consulting for unexplained infertility for at least one year. The day of their luteinizing hormone surge, 192 participants will be randomised in two equal groups to either receive 20 millilitres of physiological saline by an intra-uterine catheter or 10 millilitres of saline intravaginally. Investigators will assess relative risk of live birth (primary outcome), as well as pregnancy over one cycle of treatment. Side effects, complications, and acceptability of the intervention will be reported.

Inclusion Criteria:

• Primary or secondary infertility ≥12 months.

• Diagnosis of unexplained infertility ≤24 months:

  • Anti-Mullerian hormone ≥0.4 ng/mL and/or follicle-stimulating hormone ≤13 IU/L in early follicular phase;
  • regular cycle of 21-35 days,
  • positive ovulation tests, and/or
  • luteal phase serum progesterone ≥25mmol/L in a natural cycle;
  • semen analysis with total motile sperm count ≥ 5 million;
  • normal uterine cavity;
  • patent tubes.

• Negative genitourinary test for gonorrhoea and chlamydia ≤12 months.

Exclusion Criteria:

• Body mass index ≥35 kg/m2.
• Ongoing pregnancy.