The Effect of Aspirin on Miscarriage Risk

Woman taking aspirin
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There's a lot of conflicting information about the safety and efficacy of taking aspirin during pregnancy. Some studies say it can increase your risk of miscarriage, whereas others say the opposite. Which is correct?

Confusingly, the answer could be both—or neither. However, the research is still unclear and quite limited. In fact, there isn't much authoritative research on aspirin and miscarriage risk to go on.

What Is Aspirin?

Aspirin is a non-steroidal anti-inflammatory drug (NSAID) medication. Prescription-strength aspirin is given to relieve the pain of rheumatoid arthritis, osteoarthritis, and other rheumatologic conditions.

Nonprescription aspirin, or aspirin that can be purchased over the counter, is used to treat daily aches and pains, such as headaches. Nonprescription aspirin can also be used to treat fever. Furthermore, OTC aspirin is also prescribed to people with heart disease to prevent future heart attacks and stroke.

However, according to the National Institutes of Health, research shows that millions of people unnecessarily take aspirin preventively with no discernible benefit. This could also be the case with aspirin and miscarriage.

Aspirin and Miscarriage Risk

A handful of studies have linked NSAIDs, which include aspirin as well as pretty much every over-the-counter painkiller except Tylenol (acetaminophen), with miscarriage. However, keep in mind that the evidence is far from conclusive.

For example, a 2001 study came up with the particularly striking finding that NSAIDs during pregnancy increased the risk of miscarriage by as much as 80%. A separate 2003 study replicated the findings, noting that NSAIDs were related to miscarriage, whereas Tylenol was not, leading the authors to speculate that the NSAIDs themselves could potentially be causing the miscarriages.

Many other studies, however, have failed to establish this link, including a 2006 study that found no evidence of an association between aspirin during pregnancy and miscarriage. So, the truth isn't yet clear.

The Link Is Unclear

It could be that some other factor is responsible for the association found in the first studies, or there may have been anomalies, errors, or biases in their data. (For example, it could be that whatever condition that led women to use NSAIDs would actually be the factor increasing risk of miscarriage.)

The verdict is still out on whether aspirin plays any role in miscarriage risk.

Right now, however, in an abundance of caution, most doctors tend to lean toward Tylenol as the safest painkiller choice for pregnancy.

Could It Prevent Miscarriage?

It sounds like a contradiction to say that aspirin might also reduce the risk of miscarriage right after saying it's best to avoid using it during pregnancy. However, some limited research has shown a link with reduced risk of miscarriage in specific cases. Still, the evidence is far from clear at this point.

There's no evidence that aspirin has any benefit for the average pregnant woman, but one study published in 2008 suggested low-dose aspirin (sometimes referred to as "baby aspirin") can be useful for women who have had recurrent miscarriages associated with antiphospholipid syndrome or other blood clotting disorders.

Mini Doses for Specific Cases

Doctors often prescribe "baby aspirin" in combination with heparin or enoxaparin to prevent miscarriage in women with these conditions, and some doctors recommend aspirin to some women who have had unexplained recurrent miscarriages.

In this protocol, the dose of aspirin is typically about a fourth of what is in a standard painkiller tablet, so the effects on the body may be quite different than those of a larger dose. (And note that any aspirin use during pregnancy should be under the guidance of a physician.)

However, a 2014 study found that aspirin does not prevent pregnancy loss and should not be used for this purpose. Additionally, a comprehensive 2014 review found previous studies to be of varying (often questionable) quality and concluded: "At present, there is no evidence of a beneficial effect" of taking Aspirin to prevent miscarriage.

A Word From Verywell

Since the research is still unclear, most experts recommend avoiding aspirin while pregnant, unless your specific case warrants its use. Be sure to follow your doctor's guidance on which medications are safe for you to take while pregnant.

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