Frozen Embryo Fertilization Linked to Increased Hypertension, Preeclampsia Risks: Study

A new study warns that a potential side effect of frozen embryo fertilization procedures may include increased risks of high blood pressure and other hypertensive disorders, such as preeclampsia, which can be serious and at times fatal during pregnancy and delivery.

Prior research has highlighted the risk of hypertensive disorders among women who had in vitro fertilization using frozen embryo transfer, but the new study compared the data of more than 4.5 million women and included data to compare sibling pregnancies conceived using different methods. The findings were published September 26, in the journal Hypertension.

Fertility Treatment Hypertension and Preeclampsia Risk

Norwegian researchers conducted a population-based cohort study using Medical Birth Registries of Denmark from 1994 to 2014, Norway, and Sweden from 1988 to 2015. They compared the data to information from national quality registers and databases on assisted reproduction.

The study compared more than 4.4 million babies naturally conceived, more than 78,000 infants conceived via fresh embryo transfer including technology like in vitro fertilization (IVF), and 18,000 infants conceived via frozen embryo transfer. Researchers also compared more than 33,000 sibling pregnancies conceived using a different method than the first pregnancy.

Overall, the risk of hypertensive disorders was low, but it was higher among women who conceived using frozen embryos.

The risk of hypertensive disorders among women who used frozen embryo transfer was 7.4%, compared to 5.6% among women who used fresh embryo transfer and 4.3% for those who conceived naturally.

However, when researchers adjusted for other factors that can also lead to hypertension during pregnancy, such as high blood pressure, obesity, and age, the risk increased significantly. It was 74% higher among those who used frozen embryos compared with fresh embryo or natural conception.

The majority of the women investigated in the study who developed hypertensive disorders during pregnancy developed preeclampsia, which causes seriously high blood pressure which can lead to liver and kidney damage. It can also lead to heart attacks and stroke, and if left untreated, can be deadly.

Preeclampsia can be a life-threatening condition for pregnant women if not treated early, potentially leading to seizures and strokes. It is often preceded by high blood pressure, diabetes, and kidney disease. It is also the leading cause of pregnancy-related death worldwide, largely because hospitals are unprepared to treat the condition.

One in 12 women in the US have high blood pressure during pregnancy and 1 in 25 women will develop preeclampsia, according to the U.S. Centers for Disease Control and Prevention.

A recent study indicated nearly one-third of pregnancy-related deaths in the United States are linked to hypertensive disorders, including preeclampsia. The increase is linked to racial and ethnic disparities among women of color who do not have access to quality healthcare and face a higher risk of contributing conditions, such as diabetes and obesity.

Another study published in January indicated more than 85% of pregnant women may benefit from taking low-dose aspirin to help prevent preeclampsia. A daily low-dose of aspirin can reduce the chances of experiencing complications during pregnancy for a majority of women.

Careful Hypertension Monitoring Needed

Health experts say it is important for doctors to monitor high blood pressure during pregnancy to help avoid preeclampsia. The new data indicates women who conceived using in vitro fertilization with frozen embryos may need more careful monitoring.

Frozen embryo transfer is increasingly common in the U.S. because of improved cryopreservation methods and elective freezing of embryos. More women are conceiving at an older age and opted to freeze embryos when they were younger, but these women may potentially face a higher risk for pregnancy complications and could benefit from closer monitoring for signs of hypertensive disorders, researchers concluded.