The placenta begins to form during the second week of pregnancy and grows to keep pace with demands of the developing fetus. Normally, the placenta adheres to the upper portion of the uterine wall, well away from the cervical os and the birth canal. In one out of every 200 births, however, the placenta overlies the cervix at term, causing bleeding as changes occur in preparation for birth. The danger of hemorrhage makes the situation grave for both mother and baby. Cesarean birth is usually necessary. Uterine scars, tobacco or cocaine use, and twin/triplet pregnancies are associated with a higher incidence of placenta previa.
Abnormal Fetal Position
The majority of low-lying placentas that do not cause bleeding and are diagnosed in the second trimester will resolve without treatment. A true placenta previa at term, however, can affect fetal position. Because the afterbirth is obstructing the lower uterine segment, the baby is often more comfortable in a breech or transverse lie, with his head near the mother's heart or his body lying sideways in the uterus. The presenting part cannot be felt in the mother's pelvis during internal examinations.
Hemorrhage
The maternal and fetal bloodstreams meet, but do not mix, in the placenta. The mother's bloodstream gives oxygen and nutrients and removes carbon dioxide and other wastes from the baby's blood. Because the placenta is covering the cervix, bleeding will be fluid and bright red. A mother who has been resting in bed may pass bright red clots because blood has been pooling in the vagina. The uterus remains soft and non-tender if the mother is not in labor. Bleeding from placenta previa is painless.
Preterm Birth
Doctors may want to prolong pregnancy if bleeding is not severe and the infant is less than 34 weeks gestation. Close monitoring is usually done in the hospital. If bleeding is heavy or the infant is in distress, prompt surgical delivery gives the best chance of survival. Problems encountered by premature infants can include respiratory distress, inability to regulate body temperature and glucose, complications related to immature organs such as the liver, kidneys and digestive system and an increased vulnerability to infections. Hearing and vision loss may be side effects of medication and oxygen administration. Premature infants are often delayed developmentally, but most catch up.
Shock
Bleeding is usually noted before symptoms of shock begin, so this complication is rare unless there is a long delay in getting medical help. Dizziness is an early sign of shock. Anxiety, confusion, pale and clammy skin, fainting and rapid pulse are more severe symptoms. Fluids should be given intravenously. Provide warmth and position the victim flat on the floor with feet elevated to increase blood flow to the heart and brain.
References
- March of Dimes: Placental Conditions
- "Holistic Midwifery"; Anne Frye, 1998
