Placental insufficiency is an abnormal condition of pregnancy , in which the placenta, its membranes, or the umbilical cord develop abnormally and affect the growth of the fetus. Placental insufficiency also occurs if the placenta does not implant correctly onto the surface of the uterine wall, and can be caused by multiple pregnancies. Some conditions in the mother, such as high blood pressure, contribute to problems in the placenta. In some cases, the placental membrane can break or leak, allowing fetal blood to mix with the mother's blood. This can be associated with problems such as Rh incompatibility . See also placental failure .