According to a recent study published in Hypertension, IVF pregnancies using frozen embryos appear to be associated with a higher risk of issues related to high blood pressure than pregnancies using non-frozen embryos or natural conception.
In comparison to normal conception, the chance of developing a hypertensive problem may be 74% higher following the transfer of frozen embryos. Fresh embryo transfers seem to carry risks equivalent to those associated with pregnancies that naturally occur.
In recent years, some doctors have started skipping fresh embryo transfers in order to routinely freeze all of the embryos in their clinical practise, or the so-called “freeze-all” approach, according to Sindre Petersen, PhD, the lead study author and a fellow at the Norwegian University of Science and Technology.
Our findings show that before routinely freezing all embryos in clinical practise, it is necessary to carefully weigh all benefits and potential hazards, he said. “A thorough, tailored discussion regarding the advantages and hazards of a fresh vs. frozen embryo transfer between clinicians and patients is crucial.”
Preeclampsia is a major pregnancy complication that can be fatal to both the mother and the unborn child, according to the American Heart Association, and high blood pressure during pregnancy may be an indication of it. Preeclampsia affects about 1 in every 25 pregnancies in the United States. Preeclampsia usually results in safe pregnancies and full recovery for the moms, although it can occasionally harm the liver or kidneys and raise the risk of future cardiac problems.
In Denmark, Norway, and Sweden over the course of three decades, Petersen and colleagues examined data from medical birth registries for more than 4.5 million pregnancies. The registries had around 4.4 million naturally occurring pregnancies, 78,300 fresh embryo transfers, and 18,037 frozen embryo transfers.
In order to determine whether this potential cause of the hypertensive condition is related to parental characteristics or to IVF, researchers used a technique known as sibling comparison to analyse 33,000 pregnancies among moms who had both an IVF pregnancy and a normally conceived pregnancy.
The study’s investigators discovered that there was a 7.4% chance of hypertensive disorders throughout pregnancy following frozen embryo transfer, a 5.9% chance after fresh embryo transfer, and a 4.3% chance after natural conception.
The likelihood of preterm births increased after embryo transfer as well. Fresh embryo transfer led to about 8.1% of preterm births, followed by frozen embryo transfer with 6.6% and spontaneous conception with 5%.
The results are “in keeping with past population-level research,” according to the study authors, which demonstrate an increased risk of hypertensive problems during pregnancy following frozen embryo transfer.
For example, a French study conducted last year found that preeclampsia and hypertension risks were higher in pregnancies involving frozen-thawed embryos. Particularly, the risk increased when hormone replacement therapy were used to get the uterus ready for implantation.
“There is one thing that is unclear: Did the methodology utilised cause it, or did the actual process of freezing the embryo? Aimee Eyvazzadeh, MD, a reproductive endocrinologist in San Francisco, told CNN that the majority of IVF specialists now believe that the pharmaceutical protocol, not the IVF method, is to blame, based on current research and evidence.
She stated that there are various techniques to prepare the uterus for transfer. The corpus luteum, which creates the hormone progesterone required during pregnancy, is one method. Another method uses drugs to simulate ovulation. With frozen transfers in particular, several studies have demonstrated that the absence of the corpus luteum may raise the risk of preeclampsia.
Everyone caring for women who are pregnant following IVF should pay particular attention to this study, according to Eyvazzadeh. IVF specialists already know that IVF following a frozen embryo transfer can raise preeclampsia risk, and more and more research are confirming this.
