Does IVF Increase Risk of High Blood Pressure in Pregnancy?

Is hypertension disorder that can occur during pregnancy common during In vitro fertilization (IVF)? The freezing process of embryo might increase the risk.

Highlights:

The use of frozen embryos for In vitro fertilization (IVF) treatment is becoming more common
This frozen embryo transfer is known to be associated with a higher risk of high blood pressure
Therefore, it is necessary to find out whether this occurs to the freezing process or a risk factor from the parents

In vitro fertilization (IVF) using frozen embryos may be associated with a 74% higher risk of hypertensive disorders in pregnancy, according to new research published in Hypertension, an American Heart Association journal.

High Blood Pressure and Pregnancy

High blood pressure during pregnancy often signals preeclampsia, a pregnancy complication including persistent high blood pressure that can endanger the health and life of the mother and fetus. Approximately 1 out of every 25 pregnancies in the United States results in preeclampsia () .

One IVF treatment process available utilizes frozen embryos: after an egg is fertilized by sperm in the lab, it is frozen using a cryopreservation process before being thawed and transferred to the uterus at a later date.

In Vitro Fertilization (IVF) - Introduction To Infertility and Reproduction
Encyclopedia section of medindia gives a brief introduction to infertility and reproduction

‘In vitro fertilization (IVF) treatment process that utilizes frozen embryos might increase the risk of hypertension that occurs during pregnancy.’

The procedure is becoming more common because of the significantly improved freezing technology or cryopreservation methods that started in the late 2000s and because more patients are choosing to freeze embryos.

Yet, frozen embryo transfer is known to be associated with a higher risk of hypertensive disorders in pregnancy than both natural conception and fresh embryo transfer. However, prior to this study, it was unknown whether this was due to the freezing process or a risk factor from the parents.

Embryo Freezing for IVF Linked to High Blood Pressure in Pregnancy

Researchers examined national data from medical birth registries from Denmark, Norway and Sweden of nearly 2.4 million women who were ages 20 to 44 years old who had single deliveries and gave birth during the study period – from 1988 through 2015.

These data were the basis of a population-based study that also included a comparison of women who had both an IVF pregnancy and a naturally conceived pregnancy, called sibling comparison. This approach was used to isolate if the potential reason for the hypertensive disorders was attributable to parental factors or to the IVF treatment.

Egg Donation
The term ‘Egg Donation’ is commonly used to refer to the contribution of her eggs by a woman to another, who is incapable of producing her own.

The study included more than 4.5 million pregnancies, of which 4.4 million were naturally conceived; more than 78,000 pregnancies were fresh embryo transfers; and more than 18,000 pregnancies were frozen embryo transfers.

Among all of the pregnancies, more than 33,000 were grouped for sibling comparison – mothers who conceived via more than one of these methods. The study is the largest to-date using sibling comparison.

IVF Children at Higher Risk of Developing Hypertension
Children born through assisted reproductive technologies (ART) such as in vitro fertilization (IVF/test tube babies) may be at a greater risk of developing hypertension earlier in life.

The odds of developing hypertensive disorders in pregnancy after fresh vs. frozen embryo transfers compared to natural conception were adjusted for variables such as birth year and the mother’s age ().

This analysis found that the risk of high blood pressure in pregnancy was substantially higher after frozen embryo transfer compared to pregnancies from fresh embryo transfer or natural conception.

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Among women who had both a natural conception and an frozen embryo transfer IVF conception (the sibling comparison), the risk of hypertensive disorders in pregnancy after frozen embryo transfer was twice as high compared to pregnancies from natural conception.

This sibling comparisons indicate that the higher risk is not caused by factors related to the parents, rather, however, that some IVF treatment factors may be involved. Future research should investigate which parts of the frozen embryo transfer process may impact risk of hypertension during pregnancy ().

The study results highlight that careful consideration of all benefits and potential risks is needed before freezing all embryos as a routine in clinical practice. A comprehensive, individualized conversation between physicians and patients about the benefits and risks of a fresh vs. frozen embryo transfer is very important.

References:

Is in vitro fertilization associated with preeclampsia? A propensity score matched study - (https://pubmed.ncbi.nlm.nih.gov/24524652/)
In vitro fertilization and risk for hypertensive disorders of pregnancy: associations with treatment parameters - (https://pubmed.ncbi.nlm.nih.gov/31629726/)
Increased Preeclampsia Risk and Reduced Aortic Compliance With In Vitro Fertilization Cycles in the Absence of a Corpus Luteum - (https://www.ahajournals.org/doi/10.1161/Hypertensionaha.118.12043)

Source-Medindia