Studies suggest frozen embryos are at increased risk of hypertension-related pregnancy complications

CNN
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Pregnancies resulting from in vitro fertilization using frozen embryos appear to be associated with an increased risk of hypertension-related complications and hypertensive disorders compared to those using fresh embryos or conceived naturally.

That’s according to a study released Monday American Heart Association Journal HypertensionIt included data on over 4.5 million pregnancies over nearly 30 years in three European countries: Denmark, Norway and Sweden.

Data show that the risk of pregnancy complications associated with hypertension was higher after transfer of frozen embryos than after spontaneous pregnancy, and the risk after fresh embryo transfer was similar to that after spontaneous pregnancy.

Further research is needed to determine whether similar findings emerge in the United States.

Researchers from the Norwegian University of Science and Technology and other European institutions analyzed Danish medical birth registers dated from 1994 to 2014, Norway from 1984 to 2015, and Sweden from 1985 to 2015. . There were 4.4 million spontaneous pregnancies, 78,300 fresh embryo transfers and 18,037 frozen embryo transfer pregnancies.

The researchers compared the odds of hypertensive disorders during pregnancy between groups and found that the unadjusted risk of such disorders was 7.4% after frozen embryo transfer, 5.9% after fresh embryo transfer, and 4.3% after spontaneous conception. I discovered something. The data also showed that pregnancies from frozen and fresh embryo transfers were more frequently preterm compared to 5% of spontaneous pregnancies.

“Frozen embryo transfers are now becoming more and more common around the world. In the last few years, some doctors have begun skipping fresh embryo transfers and routinely freezing all embryos in their clinical practice. The so-called “freeze everything” approach. Principal study author Cindle H. Petersen, Ph.D., holds his Ph.D. Fellow of the Norwegian University of Science and Technology, Trondheim, Norway, said in a news release Monday.

“In summary, although most IVF pregnancies are healthy and uncomplicated, this analysis shows a significantly higher risk of hypertension during pregnancy after frozen embryo transfer compared with pregnancies with fresh embryo transfer or natural conception.” understood.”

“Our results highlight the need to carefully consider all benefits and potential risks before routinely freezing all embryos in the clinical setting,” Petersen added. I was.

The findings are “consistent with previous population-level studies” showing an increased risk of hypertensive disease during pregnancy after frozen embryo transfer, the researchers wrote in their study.

A large study from France, presented last year at the online annual meeting of the European Society for Human Reproduction and Development, also found an increased risk of pre-eclampsia and hypertension in pregnancies derived from frozen-thawed embryos. When the uterus is ready for implantation with hormone replacement therapy, it grows larger.

“The link between the frozen embryo cycle and hypertensive disease during pregnancy has been known for some time, but there is still a lively debate about the pros and cons of ‘freezing everything’. Dr. Ying Cheong, Professor of Reproductive Medicine at the University of Southampton, said: Statement distributed by UK-based Science Media Center in July. She was not involved in either study.

“There are two key points here. First, while frozen embryo transfer technology has revolutionized reproductive medicine, FET should only be performed when clinically appropriate. , we need to start connecting the dots between what happens early in development and what happens, in my opinion, the field of postnatal research is still poorly supported and researched .”

Although the new study does not assess what is driving this association between frozen embryo transfer and hypertension risk, some IVF physicians wonder whether it is really fresh or frozen. I’m here.

“There is one thing that is not clear. Is it due to the actual procedure of freezing the embryos or the protocol used? We believe it is a medication protocol rather than an in vitro fertilization procedure,” San Francisco-based reproductive endocrinologist Amy Eivazadeh, Ph.D., was not involved in the new study.

“There are different ways to prepare the uterus for implantation,” she said. One protocol includes corpus luteum cystThe corpus luteum is a fluid-filled mass that forms in the ovaries and plays an important role during pregnancy by producing the hormone progesterone needed during pregnancy. Another protocol relies on drugs that mimic ovulation.

“It is the absence of the corpus luteum that increases the risk, and research indicates that this may be the reason why cryopreservation may increase the risk of pre-eclampsia,” writes Eyvazzadeh.

Overall, the new study is “very important” for “those who care for pregnant people after IVF”, she wrote. Everyone should pay close attention to this research. What IVF doctors already know is that IVF after frozen embryo transfer may increase the risk of pre-eclampsia. There are more and more studies showing that.”