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Miscarriage

Lesson 3 of 5

Genetic Testing: Products of Conception

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Understanding Why a Miscarriage Happened

One of the biggest questions that will follow a miscarriage is why did this happen? A follow-up question is what can I do so this doesn’t happen again?

The best tool we have to understand why a miscarriage happened — and to help plan future pregnancies — is testing the pregnancy tissue (medically referred to as products of conception.)

At a high level, testing will tell you whether a pregnancy did or did not end because an embryo or fetus had genetic abnormalities. This can be both helpful for peace of mind or closure (gaining a personal understanding of “why”) and for moving forward in planning a subsequent pregnancy.

Testing After Miscarriage

What Is This Testing?

Testing after a miscarriage typically involves checking pregnancy tissue and determining its fetal karyotype; in other words, understanding from a high level whether a pregnancy had the correct genetic makeup (specifically, the right number of chromosomes).

Insights into the genetic makeup of the pregnancy will give information as to why the miscarriage happened and how future pregnancies may be impacted.

Using Results to Plan a Pregnancy

Getting a result that shows a pregnancy was chromosomally normal or abnormal can be incredibly helpful in thinking through the next steps that best match with your priorities.

If the test shows a pregnancy was chromosomally normal, that could be a crucial red flag. Before pursuing another pregnancy, it’s best to undergo more diagnostic testing to understand if a more complex issue, like a uterine abnormality, could be preventing pregnancies from continuing. It’s crucial to understand that in this case, moving on to IVF with genetic testing is not likely to improve things.

More commonly, the test shows that a pregnancy was chromosomally abnormal. In this case, it becomes a matter of personal preference as to how to move forward.

Chromosomal abnormalities are common, and that’s increasingly true with age. So, although loss of a pregnancy is devastating, one could still try to conceive again in the same way as they did in a miscarried pregnancy, with hopes that the odds are on their side.

Alternatively, if one feels that one loss was emotionally crushing and it would be impossible to endure a second miscarriage, IVF with PGT-A genetic screening could make a future miscarriage less likely. You can check out more about PGT-A testing in our dedicated course here.

Who Should Test?

Conventional wisdom used to be that post-miscarriage testing shouldn’t be done until the third miscarriage, because most miscarriages are due to random chromosomal abnormalities.

For a variety of reasons, it is the opinion of several leaders in the field of miscarriage and the opinion of FertilityIQ that, if possible, testing should happen for every miscarriage—even the first one.

A few reasons why it’s better to test on a first miscarriage:

  • If the results come back that a pregnancy was chromosomally abnormal (which is the most likely result), that can give a sense of closure, and release someone from feelings of guilt that one might have done something wrong that resulted in the loss of the pregnancy. A chromosomal abnormality shows that the loss was inevitable.
  • If the results show a pregnancy was chromosomally normal, that should be a useful red flag. It means that something else happened to result in this loss, and more testing should likely be considered to understand the other potential causes, hopefully preventing the same result in future pregnancies.

Which Test to Use?

There are several ways of testing products of conception following a miscarriage. These include tests with complicated acronyms like G-band karyotyping, FISH, Array CGH, and SNP Microarray.

For the moment, the best type of testing is using a SNP (pronounced “snip”) microarray. This modality is the only way of giving us some important information.

For example, SNP microarray is the only way to distinguish and ensure that the results you’re seeing are from the miscarriage tissue, and not cells from the mother. In the case that someone was carrying a pregnancy with a female embryo or fetus, other tests will leave this important distinction ambiguous—so you could get results that say the pregnancy tissue was genetically normal, but it’s really just that the mother’s genetics are normal.

Next, there are some subtle chromosomal abnormalities that only SNP microarray can detect. For example, there are cases when there are the correct number of chromosomes, so most tests would show a normal result, but there’s really an underlying genetic problem because all of the chromosomes came from one parent (this particular condition is a molar pregnancy).

You’ll want to check in with your doctor before the products of conception are sent out for testing to ensure that SNP microarray is what they’ll be using.

A Note on Testing Following an IVF Pregnancy

If your miscarriage was the result of a pregnancy conceived through IVF, whether or not you pursued PGT-A chromosomal screening, you can still test the products of conception.

If you did IVF without PGT-A, the testing will give you much greater insight into why the cycle didn’t work.

If you did IVF with PGT-A testing and transferred an embryo that was labeled chromosomally normal, testing products of conception will give a more definitive answer on whether or not the pregnancy was actually chromosomally normal.

Testing Miscarriage Tissues Collected at Home

If a miscarried pregnancy is removed via surgical D&C, then tissue collection for testing can be done by the surgeon and is straightforward—you’ll just have to make sure to request that it happens.

If a miscarriage instead happens outside of a doctors office, either naturally or with the help of medications, then if you’re opting to have testing done, you’ll need to collect tissue yourself.
This is not easy to go through, but it can be done.

Typically, cramping will happen, the person will sit down on the toilet, and will pass the pregnancy vaginally into the toilet bowl. The pregnancy will be able to be recovered from the toilet bowl. It will often look sort of like a marble, a tan colored marble that's been expelled.

Sometimes it's very difficult visually to distinguish the pregnancy tissue from other blood clots that might be present. One study used “toilet seat hats” with holes cut in the bottom to act as a filter—collecting the tissues, but allowing other fluids to pass through.

One study showed that 84% of those who tried this technique were successfully able to collect tissue themselves, compared with nearly 100% of a group who had tissue removed surgically.