Factors associated with the incidence of ectopic pregnancy in women undergoing assisted reproductive treatment

BACKGROUND: Ectopic pregnancy (EP) is a common complication in women undergoing assisted reproductive treatment, but the underlying causes for this remain unclear. This study aimed to explore factors affecting the incidence of EP in in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI). METHODS: This was a retrospective study on the incidence of EP in IVF/ICSI cycles between January 1, 2013 and December 31, 2017. Patient age, infertility diagnosis (tubal factor or not), primary or secondary infertility, type of cycle (frozen-thawed or fresh), type of embryo(s) transferred (cleavage embryo or blastocyst), number of embryos transferred (one, two, or three), previous history of EP, and endometrial combined thickness were analyzed to explore their relationships with the incidence of EP. Based on clinical typing results, the patients were divided into an EP group or a non-EP group. Categorical variables were analyzed using Chi-squared test or Fisher exact test. Logistic regression analysis was performed to explore their associations with the incidence of EP. RESULTS: The percentage of patients with primary infertility in EP group was significantly lower than that in non-EP group (31.3% vs. 46.7%, χ(2) = 26.032, P < 0.001). The percentage of patients with tubal infertility in EP group was also significantly higher than that in non-EP group (89.2% vs. 63.6%, χ(2) = 77.410, P < 0.001). The percentages of patients with transfer of cleavage-stage embryo or blastocyst (91.4% vs. 84.4%, χ(2) = 10.132, P = 0.001) and different endometrial combined thickness (ECT) (χ(2) = 18.373, P < 0.001) differed significantly between EP and non-EP groups. For patients who had a previous history of one to four EPs, the percentage of patients undergoing transfer of a cleavage-stage embryo was significantly higher in EP group than that in non-EP group (92.2% vs. 77.6%, χ(2) = 13.737, P < 0.001). In multivariate logistic regression analysis, tubal infertility was strongly associated with EP (adjusted odds ratio: 3.995, 95% confidence interval: 2.706–5.897, P < 0.001). CONCLUSIONS: In IVF/ICSI cycles, transfer of a blastocyst-stage embryo, especially for patients with a previous history of EP, reduced the rate of EP. Tubal infertility was strongly associated with EP.