Effect of Intrauterine Insemination on Subsequent Pregnancy Outcomes in Couples With Unexplained Pregnancy Loss: A Multicenter, Open-label, Randomized Controlled Trial

Inclusion Criteria: * Female participants aged 20-37 years. * History of at least one ultrasound-confirmed pregnancy loss (excluding biochemical pregnancy, ectopic pregnancy, and hydatidiform mole), with the most recent pregnancy loss occurring within the previous 12 months. * Desire for pregnancy at the time of enrollment. * Basal follicle-stimulating hormone (FSH) \<10 IU/L. * Anti-Müllerian hormone (AMH) \>1.1 ng/mL. * Male partner's semen analysis meeting the criteria for intrauterine insemination (IUI), with a post-processing total progressive motile sperm count ≥5 × 10⁶. * Ability and willingness to provide written informed consent. Exclusion Criteria: * Congenital or acquired uterine structural abnormalities. * Thyroid dysfunction, defined as thyroid-stimulating hormone (TSH) \>4.0 mIU/L. * Positive antiphospholipid antibodies, including lupus anticoagulant, anticardiolipin antibodies, or anti-β2 glycoprotein I antibodies. * Parental chromosomal abnormalities or a history of fetal chromosomal abnormalities in a previous pregnancy. * Participation in another interventional clinical trial during the study period.