Compared to when fresh embryos are utilised or when a pregnancy occurs spontaneously, in vitro fertilisation utilising frozen embryos appears to be associated with an increased risk of issues related to hypertensive diseases or high blood pressure.
That's according to a research that was released on Monday in the American Heart Association journal Hypertension. The study contained information on more than 4.5 million pregnancies that took place in three different European countries—Denmark, Norway, and Sweden—over a period of roughly three decades.
According to the results, the risk of high blood pressure-related pregnancy issues increased after the transfer of frozen embryos compared to normally conceived pregnancies, but the risk following the transfer of fresh embryos was identical to that of naturally produced pregnancies.
To find out if comparable results would appear in the US, more study is required.
The researchers, who are from the Norwegian University of Science and Technology and other European institutions, examined medical birth registers from Sweden from 1985 to 2015, Norway from 1984 to 2015, and Denmark from 1994 to 2014. 78,300 pregnancies using fresh embryo transfer, along with 18,037 pregnancies involving frozen embryo transfer within 4.4 million naturally occurring pregnancies, which were included in the registries.
The unadjusted risk of hypertensive disorders during pregnancy was 7.4% after frozen embryo transfer, 5.9% after fresh embryo transfer, and 4.3% after spontaneous conception, according to a study that examined the likelihood of these illnesses across the groups. The data also revealed that, compared to normally conceived pregnancies, which occur 5% of the time, preterm births from frozen and fresh embryo transfer occurred more frequently (6.6% of frozen and 8.1% of fresh, respectively).
"Our results underline the necessity for rigorous assessment of all advantages and potential dangers before routinely freezing all embryos in clinical practise," Petersen continued.