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, a study shows.

Using data from the national IVF registry of France, researchers evaluated maternal vascular morbidities in more than 68,000 singleton pregnancies.

These comprised more than 48,00 fresh-embryo transfers, 9500 natural-ovulatory-cycle frozen embryo transfers and nearly 10,400 artificial-cycle frozen-embryo transfers.

There was a higher rate of pre-eclampsia with artificial cycle frozen transfers than natural cycle frozen transfers or fresh embryo transfers (5.3% vs 2.3% and 2.4% respectively), the researchers reported at the virtual annual meeting of the European Society of Human Reproduction and Embryology.