Chromosome Miscarriage Testing
Miscarriage testing at a glance
- Chromosome abnormalities are the most common factor in miscarriages.
- Women who have had two or more consecutive miscarriages should see a fertility specialist because this increases their chances of having a successful pregnancy.
- In miscarriage testing, geneticists are able to isolate and evaluate the chromosomes of the fetus through an advanced technique called genotyping and next generation sequencing.
- The information gained from testing may or may not necessarily help avoid another miscarriage but can help bring closure to an emotionally trying experience.
What is chromosome miscarriage testing?
Women are able to have a healthy pregnancy after having a single miscarriage in as many as three out of four cases. But women having two or more consecutive miscarriages should consider seeing a fertility specialist to try to determine the cause of these multiple miscarriages.
There can be a number of causes for miscarriages, including hormonal problems, malformations and scarring of a woman’s uterus, uterine growths called fibroids, and problems with the immune system.
However, the most common cause of miscarriage is abnormalities in chromosomes, accounting for 71 percent of lost pregnancies.
Chromosomes are packages of genetic information found in every cell of the body. Normally, humans have 23 pairs of chromosomes, one inherited from each parent, including one pair that determines each person’s gender.
The term aneuploidy refers to any instance in which there is an extra or a missing copy of a chromosome. Aneuploidy is a common cause of genetic disorders, including birth defects, and is also associated with the failure of an embryo to implant in a woman’s uterus and the failure by miscarriage of a pregnancy once achieved.
More specifically, a person having one copy of a chromosome instead of two has a condition known as monosomy. Three copies of a chromosome is a condition known as trisomy. Perhaps the best-known condition resulting from trisomy is Down syndrome, in which the affected person has three copies of chromosome 21.
More than two-thirds of miscarriages in the first 12 weeks of pregnancy are aneuploid, and about three-quarters of miscarriages occur in this period, or the first trimester of a pregnancy. However, the single most common chromosome abnormality in first-trimester miscarriages is monosomy X (a condition known as Turner syndrome, which affects development in girls), followed by trisomy 16 and trisomy 22.
Another chromosome abnormality associated with miscarriages are chromosome translocation or inversion imbalances. Normally, there are the normal 46 chromosomes (23 pairs, not including the sex chromosomes), but one of the chromosomes has broken off and attached somewhere else. When the sperm or eggs are formed and fertilization occurs, unbalanced chromosome pieces can be transmitted to the embryo which would result in a miscarriage or the birth of a baby with a serious genetic condition.
Fortunately, even in cases of chromosomal abnormalities, most women are able to have a successful pregnancy after just one miscarriage. Those who have had two or more consecutive miscarriages are usually diagnosed as having recurrent pregnancy loss.
Recurrent pregnancy loss is emotionally devastating. For anyone who has undergone the experience, a laboratory test may be helpful in confirming or ruling out chromosomal abnormalities as a factor in multiple miscarriages.The information gained from testing may or may not necessarily help avoid another miscarriage. But for many couples, it can bring closure.
How miscarriage testing works
The only means of analyzing a singular miscarriage for possible chromosome abnormalities is to gather a tissue sample from the miscarried fetus. This can be difficult, of course, due to the challenges of collecting and adequately preserving the sample.
If tissue is available, geneticists can use an advanced analysis called genotyping and next generation sequencing to identify the fetus cells apart from the mother’s cells. In genotyping, geneticists examine DNA from the sample in order to distinguish the mother’s cells from those of the fetus. Next generation sequencing could identify subtle chromosome or DNA changes that could be related and causative of the miscarriage.
Benefits of miscarriage testing
If there is good news for couples that have experienced miscarriages, it’s that clinical studies have indicated that in about three out of four cases, women seeking help from a specialist after miscarrying are able to have successful pregnancies in subsequent attempts.
The specialists most qualified and experienced in helping couples to have a successful pregnancy after miscarriage are reproductive endocrinologists and infertility doctors. These physicians – known as REIs – have special training in in vitro fertilization (IVF), which is often the best approach to addressing recurrent pregnancy loss.
Frequently an REI will suggest using a technique called preimplantation genetic diagnosis (PGD) on a successive pregnancy attempt in combination with IVF in order to identify a fertilized egg (embryo) with the best chances of developing into a healthy baby.
However, maternal age is a significant factor. A woman’s odds of miscarriage increase with age, particularly after age 35. Time is of the essence, and the sooner a couple seeks expertise in dealing with recurrent miscarriages the better their chances of having a healthy baby.