/cloudfront-eu-central-1.images.arcpublishing.com/larazon/FLHZR3RQOFEBDKHTZFTFZZBMVY.jpg "Conceiving a baby from a frozen embryo increases the risk of hypertension")
In vitro fertilization (IVF) with frozen embryos may be associated with a 74% increased risk of hypertensive disorders during pregnancyaccording to new research published today in “Hypertension“an American Heart Association newspaper.
However, the researchers found that pregnancies with fresh embryo transfer (transfer of the fertilized egg immediately after in vitro fertilization (IVF) instead of a frozen fertilized egg) and naturally conceived pregnancy shared a similar risk of developing a hypertensive disorder. .
Hypertension during pregnancy often indicates preeclampsia, a pregnancy complication that includes persistent hypertension that can be life-threatening to the mother and fetus. About one in 25 pregnancies in the United States causes preeclampsia, according to the American Heart Association.
In Spain, preeclampsia can affect 7-10% of women, according to the Spanish Society of Hypertension. It is defined by an increase in blood pressure from the 20th week of gestation associated with a loss of protein in the urine.
The IVF procedure with frozen embryos is becoming more and more common due to the significant improvement in freezing technology or cryopreservation methods started in the late 2000s and also because more patients choose to freeze embryos, according to the study authors.
However, frozen embryo transfer is known to be associated with an increased risk of hypertensive disorders in pregnancy compared to natural conception and fresh embryo transfer. However, Prior to this study, it was not known whether this was due to the freezing process or a parental risk factor.
“Frozen embryo transfers are becoming more common around the world and in recent years some doctors have begun to bypass fresh embryo transfer to regularly freeze all embryos in their clinical practice, the so-called ‘freezing’ approach. Everything.” says Sindre H. Petersen of the Norwegian University of Science and Technology in Trondheim, Norway.
The researchers looked at national data from Danish, Norwegian and Swedish birth records of nearly 2.4 million women aged 20-44 who had single deliveries and gave birth during the study period, from 1988 to 2015.
These data were the basis for a population study that also included a comparison between women who had an IVF pregnancy and a naturally conceived pregnancy, called a sibling comparison. This approach was used to isolate whether the potential reason for the hypertensive disorders was attributable to parental factors or to IVF treatment.
Research found that between women who had one pregnancy by natural conception and another by IVF frozen embryo transfer (the sibling comparison), the risk of hypertensive disorders in pregnancy after frozen embryo transfer was twice as high as in conceived pregnancies natural. A difference that did not occur in sibling pregnancies from fresh embryos compared to natural conception.
The study included more than 4.5 million pregnancies, of which 4.4 million were naturally conceived3, more than 78,000 were fresh embryo transfers, and more than 18,000 were frozen embryo transfers.
Of all the pregnancies, more than 33,000 were collected for sibling comparison – mothers who conceived with more than one of these methods. The study is the largest to date using sibling comparison.
“Our sibling comparisons indicate that the increased risk is not caused by parental factors, but that some IVF treatment factors may still be involved,” Petersen says.
“Future research should investigate which parts of the frozen embryo transfer process may influence the risk of hypertension during pregnancy.”
Among other findings, women in the study who gave birth after an IVF pregnancy had an average age of 34 for frozen embryo transfer, 33 for fresh embryo transfer, and 29 for those who conceived naturally.
About 7% of babies conceived by frozen embryo transfer were born preterm (before 40 weeks of gestation) and 8% of babies conceived by fresh embryo transfer were born preterm, compared with 5% of babies conceived naturally.
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