Emily Oster

3 min Read Emily Oster

Emily Oster

How Likely is Another Miscarriage After an Unexplained One?

Q&A on data

Emily Oster

3 min Read

I had a missed miscarriage, caught at 12.5 weeks. This was following a normal NIPT, and the pregnancy tissue analysis showed normal chromosomes. My subsequent blood workup (A1C, lupus, chromosomes) was also normal. Throughout my pregnancy I was reassured at each check-in of the drop in miscarriage probability. Following, I was told the most likely case was chromosomal anomaly. Now I’m told the likelihood of repeated miscarriage is small. After experiencing the unlikely outcome at each turn, how would you approach data for subsequent pregnancies — and what really is the risk for repeated MC after a miscarriage not due to chromosomal anomaly or underlying health risk?

—Unlikely outcome

This is a tough question for a lot of reasons. Let me say first I’m so sorry for your loss, and I wish you had more answers. 

I want to address your two questions separately here: what the risk is for another miscarriage and how to approach the data

In general, after a single first-trimester miscarriage, there is only a small elevation in the risk of a second. This is why generally doctors will not do any additional testing after one pregnancy loss. In about 90% of cases, the cause is a chromosomal abnormality. In your case, even with the testing you’ve done, this is still a very real possibility. There are abnormalities that wouldn’t be picked up on the more standard analyses. 

In a case like yours, where you’ve ruled out the primary chromosomal issues, there is a larger chance that there is something systematic going on. In The Unexpected, we talk through a few possible explanations, most of which are quite rare. Even with the testing, the most likely explanation is simply that this occurred by chance. It is likely the medical advice will be to do nothing and simply try again.

In that case, we get to the second question — how to consider the data and whether your approach should be different. The answer, I think, is no. Even if you accept that what happened to you was unusual, unusual events do happen. It is not clear that you should learn much from this about what to do going forward.

If you were a robot, this answer would be helpful. As a person, it may be less so. We are designed to learn from our experiences, and when something has happened to us before, it becomes more salient, more a part of our expectations. Our own estimate of the chance of it happening goes up, even if the data says it shouldn’t. In these cases, often the best we can do is try for a kind of radical acceptance that what happened to us was just bad luck. 

I’ll be thinking about you.

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6 months ago

I’m so sorry this happened to you. I experienced a devastating missed miscarriage myself. It was followed many years later by a healthy pregnancy. It sounds like you’ve done many tests, but please also talk with your provider about checking your thyroid. My thyroid demands went way up in pregnancy and TSH tests were no longer normal after my missed miscarriage. Only after getting on thyroid medication did I have a successful pregnancy (two other early losses along with my missed miscarriage). It may not be relevant for you, but TSH is a simple blood test. Best of luck!

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