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.