Recurrent Pregnancy Loss and PGD

Although it is not an uncommon event, it's a devastating experience to lose a pregnancy in miscarriage. If this has happened to you, you're not alone. Up to one in four pregnancies end in first trimester miscarriage and the chance increases with the age of the mother.

Having more than one miscarriage is less common and only about 1-2% of fertile couples experience three or more miscarriages. Many of these couples are afraid to try again because they don't want to face the possibility of the pain and grief of another loss.

If you've gone through the trauma of recurrent pregnancy losses, what are your reproductive options? First, many doctors recommend a medical work-up to look for potential causes for the miscarriages. This work-up may include some or all of the following tests:
evaluation of the woman's uterus; blood tests for hormone levels,
infections,
certain antibodies,
blood clotting factors and other factors that may contribute to pregnancy loss, and
other specific tests on either member of the couple as indicated by their medical histories.

In addition, it is a standard that couples who have had three (sometimes two) or more first trimester losses be offered a blood test called a chromosome analysis - also called a karyotype - to look for balanced chromosome rearrangements. About one in 20 couples with three or more miscarriages will have one partner with a balanced chromosome rearrangement - either a translocation where two chromosomes have switched pieces; or an inversion in which part of a chromosome has flipped upside down. People with these chromosome changes are at significant risk for miscarriage with each conception. Their reproductive options include trying until they achieve an ongoing pregnancy or using a technology called Preimplantation Genetic Diagnosis (PGD) along with in vitro fertilization (IVF) in order to select embryos free of unbalanced chromosome abnormalities which are more likely to create ongoing healthy pregnancies. This type of testing will be discussed further in a future article.

What about couples who have gone through a full medical work-up and no cause has been found for their losses? Unfortunately, this is not uncommon; about 1/2 of couples with recurrent miscarriages are left with no specific answers. What do we know in this situation? Well, first, we know that over 50% of all first trimester miscarriages are caused by chromosome abnormalities - extra or missing whole chromosomes that occur by chance when the egg or sperm is formed - a condition called 'aneuploidy'.

We also know that couples who have had a pregnancy loss with a documented chromosome abnormality are at slightly increased risk to have another pregnancy with a chromosome abnormality. In addition, a number of recent studies suggest that some couples with recurrent pregnancy losses in which no cause for the miscarriages has been identified appear to have a higher number of embryos with chromosome abnormalities than expected. Couples in either of these situations - prior pregnancy with an identified chromosome abnormality or unknown cause for their losses - have the opportunity to consider another reproductive option instead of 'trying again'.

Preimplantation Genetic Diagnosis (PGD) for aneuploidy, also called Preimplantation Genetic Screening (PGS) - is used along with in vitro fertilization (IVF) to screen one cell of an early embryo for extra or missing chromosomes. Over 90% of embryos with aneuploidy will either not implant or will end in early miscarriage, generally before the end of the first trimester. Other forms of aneuploidy can results in later miscarriage, stillbirth or the birth of a baby with a chromosome syndrome such as Down syndrome.

By testing embryos prior to transfer to the mother's uterus, you and your IVF doctor have the opportunity to choose to transfer those embryos most likely to have normal chromosomes, and, therefore, most likely to implant, and least likely to miscarry. A number of studies have suggested that PGD for aneuploidy may be beneficial in reducing the rate of miscarriage for couples with recurrent pregnancy loss.

Many couples who have experienced recurrent pregnancy loss have successful natural pregnancies without IVF and PGD for aneuploidy; in fact, research data indicates that even after three losses, the chance of having a subsequent successful pregnancy is about 40%. However, couples that want to attempt to lower their chances for miscarriage and increase their chances for ongoing pregnancy do have the option of IVF with PGD for aneuploidy.

Barbara Pettersen, MS, CGC - Manager, Genetic Counseling Services at Gene Security Network (GSN) Barbara Pettersen is a board certified genetic counselor who has worked in the field of clinical genetics for over 26 years. She is using her expertise in preimplantation genetic screening at GSN to help families in their quest to have children free of serious genetic conditi

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