Introduction
Intrauterine insemination (IUI), a minimally invasive and low-cost procedure, is a first-line treatment for a broad range of indications in reproductive medicine 1,2. IUI involves timely scheduled insemination of sperm into the uterus, either in natural cycles or following ovarian stimulation. Compared to stimulated IUI, natural cycle IUI is preferable for patients because of advantages including lower medication cost and reduced rates of multiple gestation3.
It is known that the timing of insemination is one of the most impactful factors influencing the success rates of IUI 4, 5. There are various methods for timing IUI, and administration of human chorionic gonadotropin (hCG) is a widely accepted in clinical practice. Administration of hCG requires less endocrine monitoring, but its effect on endometrial receptivity has drawn extensive attention recently6- 8.
Multiple clinical studies have assessed the effect of hCG on pregnancy outcomes, but have reached inconsistent conclusions9-12. Such conflicting results result from clinical indication, female age, baseline characteristics of study participants, sperm quality, timing, or type of ovarian stimulation.
The current study examined a large cohort of women undergoing natural cycle IUI and aimed to assess the effect of hCG-induced ovulation on pregnancy outcome of natural cycles IUI. Attempting to control for sperm-related factors, this retrospective study only examined patients using donor sperm.