How Common Is Bleeding in the First Trimester?

How common is it to have bleeding and spotting at any point in your first trimester? When I talked to my OB about it, she said it was fine, but I’m still worried. Am I at higher risk for miscarriage? How much blood is too much?

–Kayla

About 25% of women will have bleeding in the first trimester of pregnancy. This can happen for many reasons, including changes in hormones, implantation, and other factors. It is also true — and this is where your concern is reasonable — that bleeding occurs with a miscarriage. The important question is whether any bleeding indicates an increased risk.

This question is well answered by this study, which followed over 4,000 people through their pregnancies and in which 27% of women reported at least one episode of bleeding in their first trimester. Of those with bleeding, most reported only one episode, but 10% of the sample reported three or more bleeding episodes; each of these episodes could last several days.

The authors of the study distinguish between spotting, light bleeding, and heavy bleeding. Spotting was blood that was only noticed when wiping. Light bleeding was defined as bleeding that was lighter than the heavy flow of a normal menstrual period. Heavy-bleeding episodes were those with at least one day that was as heavy or heavier than the heavy flow of a usual menstrual period. Of the women who reported bleeding, 8% of them reported heavy bleeding by this definition.

What the authors found is that spotting or light bleeding was not associated with an elevated risk of miscarriage. They did find that heavy bleeding was associated with miscarriage — about 25% of the sample with heavy bleeding miscarried, which was about three times as high as the average risk.

Putting this together: the vast majority of women with bleeding during early pregnancy do not miscarry, and, indeed, for most levels of bleeding it is not even informative about this risk. Heavy bleeding is associated with an increased risk of pregnancy loss, but even among those who have heavy bleeding during the first trimester, 75% of them do not miscarry.