HealthDay News — Frozen embryo transfer (ET) is associated with a substantially higher risk for hypertensive disorders in pregnancy, according to a study published online September 26 in Hypertension.

Sindre H. Petersen, MD, from the Norwegian University of Science and Technology in Trondheim, and colleagues used data from the Medical Birth Registries of Denmark (1994 to 2014), Norway, and Sweden (1988 to 2015) linked to data from national quality registries and databases on assisted reproduction (4.4 million naturally conceived, 78,300 fresh ET, and 18,037 frozen ET singleton pregnancies) to assess parental and fertility treatment factors associated with hypertensive disorders.

The researchers found that the risk for hypertensive disorders in pregnancy was higher after frozen ET vs natural conception, both at the population level (7.4 vs 4.3%; adjusted odds ratio [aOR], 1.74; 95% CI, 1.61 to 1.89) and within 33,209 sibships (aOR, 2.02; 95% CI, 1.72 to 2.39). Risk was similar to natural conception for fresh ET, both at the population level (aOR, 1.02; 95% CI, 0.98 to 1.07) and within sibships (aOR, 0.99; 95% CI, 0.89 to 1.09).

“Our results highlight that careful consideration of all benefits and potential risks is needed before freezing all embryos as a routine in clinical practice,” Petersen said in a statement. “A comprehensive, individualized conversation between physicians and patients about the benefits and risks of a fresh versus frozen embryo transfer is key.”

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