Japanese researchers explored a national database to determine whether thawed single-blast embryo transfer in natural cycles would reduce the risk of an ectopic pregnancy.
Take Home Message:
The cause of ectopic pregnancy after IVF embryo transfer has been unclear. This study suggests that the stimulated cycle with IVF may be a large contributor. The risk is still low from high of 2.4% in fresh cleaved-embryo transfer to low of 0.8% in frozen blast transfer.
Topical pregnancy seems to have a higher incidence after embryo transfer with the incidence and varying from 2.% to 8.6%. The incidence of ectopic pregnancy in a spontaneous conception ranges from 2.2% to 4.5%. Reason for the increase in ectopic pregnancy is not clear.
Some factors thought to contribute to the increased risk include:
- Tubal disease is a common reason for using IVF, particularly in the early years of IVF treatment
- The technique of embryo transfer
- Transfer of embryos 3 days after retrieval means that the embryos sit in the endometrial cavity for 2-3 days before implantation (which is similar to natural conception) but this may give the embryo more time to migrate into the tube
- The IVF cycle requires significant ovarian stimulation and the hormone environment is not optimal for embryo implantation, at least in theory
The study was interesting because a used a national registry of information allowing them to accumulate a very large sample size (58,646 frozen embryo transfer cycles), a large number of single embryo transfer cycles (38,389), and the Japanese practice of using natural menstrual cycles for transfer unless the woman has ovulatory dysfunction.
Their data showed the following:
- The odds ratio of ectopic pregnancy after frozen thawed transfer was 0.6
- The odds ratio of ectopic pregnancy after blastocyst transfer compared to cleaved embryo transfer was 0.61
- The rate of ectopic pregnancy decreased with increasing age with fresh cleaved embryo eSET
- The rate of ectopic pregnancy did not change with age in frozen cleaved embryo eSET
- The rate of ectopic pregnancy remained the same at all ages with blastocyst transfer eSET, both fresh and frozen cycles
Frozen-thawed blastocyst transfer reduces ectopic pregnancy risk: an analysis of single embryo transfer cycles in Japan
Osamu Ishihara MD, Akira Kuwahara MD, Hidekazu Saitoh MD
Fertility and Sterility Volume 95, Issue 6 , Pages 1966-1969, May 2011