Ovulation triggers can increase the risk of ectopic pregnancy

This study examined whether gonadotropin-releasing hormone agonists increase the risk of ectopic pregnancy following in vitro fertilization.

Between 2.1% and 8.6% of in vitro fertilization cycles (IVF; an assisted reproductive technique in which the egg is fertilized outside of the body and then implanted) result in ectopic pregnancy, a pregnancy that does not implant in the uterus but begins to grow in the Fallopian tube. This is a potentially life-threatening condition if not diagnosed early. It is not clear why IVF raises the risk for ectopic pregnancy, but possible reasons include the controlled hormonal process necessary for ovarian stimulation, the underlying reason for infertility, or the IVF procedure itself.

IVF involves the use of a trigger, a hormone used to stimulate ovulation at the correct time. Human chorionic gonadotropin (hCG) is classically used, but this can increase the risk of ovarian hyperstimulation syndrome (painful, swollen ovaries, which can lead to a serious increase in fluid in the abdomen or chest). Another type of trigger, gonadotropin-releasing hormone agonists (GnRHa), lower the risk of ovarian hyperstimulation syndrome, but lower pregnancy rates and increase pregnancy loss rates, possibly by decreasing the receptiveness of the uterus to implantation. This study examined whether GnRHa also increased the risk of ectopic pregnancy following in vitro fertilization.

This retrospective study examined the records of 466 women who underwent IVF during a 2-year period. 114 women were given a GnRHa ovulation trigger, and 352 were given an hCG trigger. There were a total of 1,003 embryos transferred. Pregnancy was determined at 12 days post-transfer by measuring the level of beta hCG in the blood, a hormone that rises rapidly in early pregnancy. This was measured every 2-4 days until a heartbeat was seen with an ultrasound. Women who saw a rise in beta hCG but did not display an embryo in the uterus were given further tests to determine if the pregnancy was ectopic.

The implantation rate was 31.1% for women given an hCG trigger and 22% for those given a GnRHa trigger. The early loss rate was 17.3% following the hCG trigger and 37.7% following GnRHa.

The overall ectopic pregnancy rate was 2.3%. The ectopic pregnancy rate for women given the hCG trigger was 1.4%, and the rate for women given the GnRHa trigger was 5.3%. The hCG trigger decreased the odds of ectopic pregnancy by 75% compared to the GnRHa trigger.

This study concluded that the use of a gonadotropin-releasing hormone agonist trigger increased the risk of ectopic pregnancy compared to a human chorionic gonadotropin trigger in women undergoing in vitro fertilization.