A condition prior to the 20th week of gestation characterized by uterine bleeding and cramping that suggests a miscarriage may result. It can generally be managed with complete rest and medical observation.

Traditionally, any bleeding from the uterus during pregnancy while the cervix is (still) closed. Today, as well, there would need to be a normal embryo and, a little later, normal fetal heart movement pattern on transvaginal ultrasound to separate it from an inevitable miscarriage.

Anytime there is vaginal bleeding during the first half of pregnancy, the pregnancy is considered threatened. The expectant mother may undergo a physical examination and tests to determine the cause of the bleeding, and treatment will be initiated if necessary.