Bloody show

Bloody show is the passage of a small amount of blood or blood-tinged mucus through the vagina near the end of pregnancy. It can occur just before labor or in early labor as the cervix changes shape, freeing mucus and blood that occupied the cervical glands or cervical os. Bloody show is a relatively common feature of pregnancy, and it does not signify increased risk to the mother or baby. A larger amount of bleeding, however, may signify a more dangerous, abnormal complication of pregnancy, such as placental abruption or placenta previa. Large amounts of bleeding during or after childbirth itself may come from uterine atony or laceration of the cervix, vagina, or perineum.

Three common signs of the onset of labor are:

However, these may occur at any time and in any order. Some women neither experience a bloody show nor have their "water break" until well into advanced labor. Therefore, neither bloody show nor rupture of membranes are required to establish labor.

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Wikipedia