Can freezing IVF embryos reduce pregnancy complications?

Babies conceived by IVF have a higher risk of complications and stillbirth. Our scientists want to find out why these risks appear to be reduced when an IVF embryo is frozen before it is transferred into the mother’s womb, rather than being transferred fresh.
  • Author's list

    Dr Lucy Higgins, Professor Daniel Brison, Dr Mark Dilworth, Professor Ed Johnstone, Professor Alexander Heazell

    Start date: April 2020
    End date: 2023

  • Research centre

  • Research status

    Ongoing projects

Why do we need this research?

Couples who can’t get pregnant naturally can opt for in vitro fertilisation (IVF), where the egg is fertilised by sperm outside the body. However, we know that IVF pregnancies have a higher chance of complications, including stillbirth and death shortly after birth.

We need to understand why this is the case, and what can be done to reduce the risks for babies conceived by IVF.

What’s happening in this project?

After IVF, embryos can either be transferred ‘fresh’ into the mother’s womb, or frozen first and transferred later. Researchers have noticed that babies from frozen IVF embryos tend to grow faster during pregnancy compared to babies from fresh IVF embryos. However, it is not clear why.

A lot of pregnancy complications are caused by problems with the placenta. This has led our researchers to believe there might be differences in the placentas of babies born from ‘fresh’ IVF embryos versus those from frozen embryos. Our scientists will test this theory in this project.

The team will study the placentas of babies born following IVF treatment – some after fresh embryo transfer and others after the embryos are frozen. They will be looking at the weight and size of the placenta, and will also study the cells and blood vessels inside it. The team will ask the women for blood samples throughout pregnancy so that they can look for hormones in the blood that are related to how blood vessels and the placenta develop.

What difference will this project make?

This project will help us to understand why IVF pregnancies have a higher risk of complications. If pregnancy complications such as stillbirth and miscarriage are found to be reduced when IVF embryos are frozen before the transfer, this could become a standard part of IVF treatment.