Lies, Damned Lies, and Miscarriage Statistics

Trying to figure out your chances of miscarrying? Sadly, you are going to have a hard time finding good information. 

Many websites claim to tell you your risk of miscarriage, citing statistics that look like these:

Chart shows commonly stated chances of miscarriage by pregnancy week. For 1-2 weeks, the chances are 75%. For weeks 3-6 the chances are 10%. For weeks 6-12 the chances are 5%, and for weeks 12-20, the chances drop to 3%.
Commonly reported chances of miscarriage by pregnancy week

But problems abound with their numbers.

Problem 1: These sites rarely provide their sources, so you cannot tell whether their information is reliable.

Problem 2: These sites do not breakdown miscarriage risk by other known risk factors, like the mother’s age.

Problem 3: Nearly all these sites derive their statistics from just two small studies, one which tracked 222 women from conception through just the first 6 weeks of pregnancy, and another which tracked 697 pregnancies, but only after a fetal heartbeat had been detected–a key point, because heartbeat detection dramatically lowers the chances of a miscarriage.

The lack of good information frustrated me when I was pregnant, and I bet it frustrates you too. So I have compiled a summary of the best research on risk of miscarriage. Where possible, I break down the risk by…

Edit: I also have a new post on how morning sickness signals a lower risk.

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