Objective: Ectopic pregnancy is a well-known complication following in vitro fertilization with embryo transfer; studies have questioned, however, whether there are risk factors that could be identified before the procedure. The objective of this study was to investigate the possible risk factors involved in ectopic pregnancy following in vitro fertilization.
Methods: Retrospective case-control study performed at an assisted reproduction clinic in Brazil. To select the control group, we used a 1:4 ratio. The study included 499 patients submitted to in vitro fertilization with clinical pregnancy. We collected the data from electronic records, between 2000-2019 and divided into: Group 1, ectopic pregnancy (n=90) and Group 2, intrauterine pregnancies (n=409).
Results: When comparing groups, the results observed were: Tubal factor infertility (35.6% vs. 21.1%, p=.005) (OR 2.0 [1.2-3.4], p=.004); Previous miscarriage history (15.1% vs. 7.1%, p<.05) (OR 2.0 [1.02-4.29], p=.044); Number of cleavage-stage embryo transfers (69.2% vs. 54.0 p=.028) (OR 1.9 [1.08-3.33], p=.025); Two or more embryos transferred (OR 2.5 [1.12-5.70], p=.025), all associated with greater ectopic pregnancy risk. Oocyte recipient patients were excluded from this analysis, but when included a difference was found when comparing the groups (9.4% (10/106) vs. 3.0% (13/434), p=.007), (OR 3.3 [1.41-7.98] p=.005); this result should be interpreted with caution because of the sample size.
Conclusions: In high-risk patients, a single blastocyst transfer seems to be a reasonable approach to decrease the ectopic pregnancy risk.
Keywords: Ectopic pregnancy; in vitro fertilization; risk factors.