Artificial-Cycle Frozen-Embryo Transfer for IVF May Raise Risk of Vascular Problems in Pregnancy

By Megan Brooks

July 09, 2021

NEW YORK (Reuters Health) - Artificial priming of the uterus with hormone therapy before transfer of a frozen embryo may increase the risk for pre-eclampsia and pregnancy-induced hypertension, according to new findings.

Because in vitro fertilization (IVF) results obtained with a "natural" ovulatory cycle do not hinder the chances of pregnancy, "this preparation could be advocated as first-line endometrial preparation in frozen-thawed embryo transfer as often as the choice is possible in ovulatory women," Dr. Sylvie Epelboin, from the Hopital Bichat-Claude Bernard in Paris, France, told Reuters Health by email.

Using data from the national IVF registry of France, the researchers evaluated maternal vascular morbidities in more than 68,000 singleton pregnancies, including 48,152 fresh-embryo transfers (fresh-ET), 9,500 natural-ovulatory-cycle frozen embryo transfers (OC-FET) and 10,373 artificial-cycle frozen-embryo transfers (AC-FET).

There was a higher rate of pre-eclampsia with AC-FET (5.3%) than OC-FET (2.3%) and fresh-ET (2.4%), Dr. Epelboin and her colleagues report at the virtual annual meeting of the European Society of Human Reproduction and Embryology. The rate of pregnancy-induced hypertension was also higher with AC-FET than OC-FET and fresh-ET (4.7% vs. 3.4% and 3.3%).

These differences were statistically significant, even after adjusting for a wide variety of characteristics of the mother including age, parity, tobacco use, obesity, history of diabetes, hypertension, endometriosis, polycystic ovaries, and premature ovarian failure.

"In the case of artificial cycle, high supra-physiological and prolonged doses of hormonal therapy are needed during the early development of pregnancy. This study demonstrated that FET preparation by artificial cycle was significantly associated with an increased risk of vascular disorders compared to ovulatory cycle and fresh-ET," Dr. Epelboin told Reuters Health.

"The conclusion of this study is in no way a recommendation against frozen-thawed embryo transfer, embryo freezing being a major breakthrough among assisted reproductive technology (ART)," Dr. Epelboin emphasized.

"The recommendation is to continue the policy of embryo freezing, which is beneficial in many respects," she added, and to choose frozen-embryo transfers with the natural ovulatory cycle or mild stimulation rather than the artificial cycle if possible.

SOURCE: European Society of Human Reproduction and Embryology, presented June 30, 2021.