Does genetic testing improve birth rate?

This review looked at whether genetic testing improved the birth rate from in vitro fertilization (IVF). It found that testing improved birth rates for women over age 35.

IVF is a common infertility treatment in which eggs are stimulated and collected, and fertilized embryos implanted back in the uterus. When IVF embryos are frozen, it is possible to use pre-implantation genetic testing for aneuploidy (PGT-A). This procedure involves taking a biopsy of the embryo, and testing whether it has the normal number of chromosomes (pieces of genetic material). Some embryos with the wrong number of chromosomes will end in miscarriages. Other embryos with unusual chromosomes will result in children with genetic conditions such as Down syndrome.

Eggs and sperm have half as many chromosomes as other cells in the body. Sperm completes this division during sperm development. However, oocytes (eggs) do not finish dividing their chromosomes until the start of fertilization. This process is more likely to have an error when a woman is over age 35. However, an error in the number of chromosomes can happen with either sperm or eggs. 

Because aneuploid embryos can result in miscarriage, it is possible that PGT-A testing could reduce miscarriages. However, PGT-A can also reduce the number of embryos available to be implanted. It is not clear how PGT-A testing affects birth rates for couples using IVF.

This review included 11 trials where patients using IVF were randomly assigned to one of two groups. Most of the studies compared PGT-A to no PGT-A. Some studies compared PGT-A on different days.

Six studies with 1513 patients looked at whether PGT-A affected birth rates. There was no clear increase in births when using PGT-A. However, the researchers also looked specifically at the 629 women over age 35. For women over age 35, PGT-A significantly increased birth rates by 29%.

Looking at all ages, PGT-A significantly reduced miscarriages by 55%.

Embryos can be biopsied for PGT-A either 3 days or 5 days after fertilization. Compared to no test, day 3 PGT-A  trended toward increasing live birth by 26%. However, only day 5 PGT-A significantly increased births by 37% compared to no test.

This analysis found that PGT-A reduced miscarriages, and for women, over age 35 PGT-A increased birth rates.

It is possible for an embryo to be “mosaic,” or to contain both normal cells and cells with an abnormal number of chromosomes. Some mosaic embryos can form healthy babies because the abnormal cells stop growing. The studies in this review varied in how they accounted for mosaic embryos.

Ask your doctor whether PGT-A is right for you if you are using IVF and over age 35.