Association of endometrial preparation protocols and embryonic development stages with ectopic pregnancy in...

To investigate the correlation between endometrial preparation protocols, embryonic development stages, and ectopic pregnancy.

A total of 29,700 clinical pregnancies, all of which resulted from freeze-thaw cycles performed between January 2018 and December 2023, were analyzed in this retrospective study.

The ectopic pregnancy rate was significantly higher in artificial cycles than natural cycles (1.5% vs. 0.8%; P < 0.001); the ectopic pregnancy rate was significantly higher in stage 5-6 than stage 3-4 blastocyst transfer (1.3% vs. 0.7%; P = 0.019). After incorporating all independent confounders into a multivariate general estimating equation model, artificial versus natural cycle (adjusted RR = 1.68, 95% CI = 1.32-2.13; P < 0.001) was shown to be an increased risk factor for ectopic pregnancy, especially in the single embryo transfer subgroup (aRR = 1.75, 95% CI = 1.23-2.48; P = 0.002); additionally, day 3 embryo transfer versus blastocyst transfer (aRR = 1.97, 95% CI = 1.15-3.38; P = 0.014) and stage 5-6 blastocyst versus stage 3-4 blastocyst transfer (aRR = 1.70, 95% CI = 1.05-2.74; P = 0.031) were shown to be increased risk factors for ectopic pregnancy.

This study found that endometrial preparation protocols and embryonic development stages are significantly associated with ectopic pregnancy.