Pregnancy bleeding ranges from light pink or brown spotting to heavy, bright red blood. The color, amount, and timing all provide important clues about the cause. Brown blood is typically older blood that has taken time to leave the body and is often less concerning. Bright red blood is fresh and may indicate active bleeding. Pink spotting is often diluted blood mixed with cervical mucus.
In the first trimester, the most common benign cause is implantation bleeding — light spotting that occurs 6 to 12 days after conception when the embryo burrows into the uterine lining. Up to 25 percent of pregnancies involve some first-trimester bleeding, and more than half of these result in healthy, full-term pregnancies. Other first-trimester causes include cervical irritation (the cervix has increased blood supply during pregnancy), subchorionic hematoma, and less commonly, ectopic pregnancy or miscarriage.
In the second and third trimesters, bleeding can be caused by cervical changes, placenta previa (placenta covering the cervix), placental abruption (placenta separating from the uterine wall), or preterm labor. Any bleeding after the first trimester should be evaluated promptly.