Is the thickness of the womb lining related to ectopic pregnancy risk?

This study compared women who had an ectopic pregnancy (EP) vs a normal pregnancy following in vitro fertilization (IVF). It found that a thick lining of the womb protects against EP, and pelvic surgery and tubal-related infertility are risk factors for EP.

Ectopic pregnancy (EP) is when an embryo implants somewhere other than in the endometrial lining (lining of the womb). Most EPs are within the Fallopian tubes, which lead from the ovaries to the uterus. EP is rare, but it is life-threatening if it is not recognized and treated early. The rate of EP is higher after IVF than after unassisted conception. IVF is an infertility treatment in which fertilized embryos are placed in the woman’s womb. It is not clear why IVF increases the risk of EP.

This study compared 225 patients who had an EP following IVF to 900 patients who had a normal pregnancy following IVF. The two groups were similar in terms of age, weight, time trying to conceive, and sperm quality. However, the antral follicle count (AFC) was significantly higher in women who had an EP. AFC is related to the remaining number of eggs in the ovaries.

Women who had previously had a cesarean section had a 67% higher risk of an EP. Women who had previously had pelvic surgery other than a cesarean section had 2.07 times higher risk of an EP. Women whose infertility was due to abnormalities in the Fallopian tubes had a 61% higher risk of EP.

Women who had a thick endometrial lining prior to the embryo transfer (over 12 mm) were 73% less likely to have an EP. Also, women whose IVF cycle created a higher number of transferable embryos were 29% less likely to have an EP. This may be because the number of transferable embryos per cycle is related to embryo quality.

This study found that pelvic surgery and tubal-related infertility were significantly associated with a higher risk of EP. Also, a thick endometrial lining was significantly associated with a lower risk of EP.

Studies of women not using IVF have found high body weight and previous EPs are risk factors for EP. This study was not able to determine the causes of EP, only relationships.

Discuss possible complications including EP with your provider when considering IVF.