During pregnancy, a woman's uterus houses and protects a developing fetus for approximately 40 weeks. Inside the uterus, the fetus is tethered to its mother via the umbilical cord, which is attached to the uterine wall by a mass of tissue called the placenta. The placenta and umbilical cord transport oxygenated blood and nutrients from the mother to the developing fetus and return waste products from the fetus to the mother's circulation for removal. Injury resulting from automobile accidents or serious falls can cause the placenta to separate from the wall of the uterus prematurely, a condition known as placenta abruptio. If the separation is minor and only a small amount of vaginal bleeding is present, the pregnant woman will be treated with fluid replacement and bed rest. However, if the separation is more substantial, or if the placenta is completely disjoined from the uterus, the mother and baby may be in serious jeopardy. Abdominal pain and a large amount of darkly colored blood coming from the vagina may indicate that an emergency delivery or cesarean section is required. It is also important to note that placenta abruptio may also occur spontaneously in a woman who has had many previous deliveries, has a history of placenta abruption or is carrying multiple fetuses. Additional risk factors may include medical conditions such as hypertension and diabetes, as well as cigarette smoking, and alcohol or drug abuse.