Amniotic Fluid Disorders and Pregnancy Complications
Throughout pregnancy a fetus is surrounded by amniotic fluid. Amniotic fluid is a clear fluid that protects the fetus during the pregnancy, providing a safe environment in which the fetus can grow and move. As the fetus develops, it both swallows and breathes in amniotic fluid, and the fluid aids in the development of the lungs, kidneys and gastrointestinal tract.
In a normal pregnancy approximately 500 ml of amniotic fluid is produced. In almost seven percent of pregnancies, amniotic fluid problems develop. Imbalances in amniotic fluid volume can cause pregnancy complications. In very rare events, amniotic fluid may even pass through the placenta and enter the mother's bloodstream, causing a life-threatening pregnancy complication called amniotic fluid embolism.
Oligohydramnios
Pregnant women with low levels of amniotic fluid have a condition known as oligohydramnios. Ultrasound can identify oligohydramnios, which may be caused by ineffective placental flow. Oligohydramnios may also be caused by low fluid production from the fetus' lungs and kidneys, or a rupture of the amniotic membrane,(the membrane that surrounds both the fetus and the amniotic fluid.
Complications of Oligohydramnios
In most cases of low amniotic fluid, pregnancy ends with a healthy baby. However, oligohydramnios is more serious when it occurs in the first half of a pregnancy. Low levels of amniotic fluid increase the chance of miscarriage, premature births and stillbirth. In addition, oligohydramnios, especially early in pregnancy, carries a greater risk of lung and limb defects. Insufficient amniotic fluid can compress fetal lungs and cause kidney and urinary tract problems. Overall, seven percent of infants who experience oligohydramnios have some degree of birth defects.
Treatment for Low Amniotic Fluid Levels
Treatment depends on how far the pregnancy has progressed. If the pregnancy is at term, delivery is the best treatment. If the pregnancy is not far enough along to recommend delivery, amniotic infusion may be suggested. An amniotic infusion injects additional amniotic fluid through the amniotic membrane to raise fluid levels.
Polyhydramnios
Polyhydramnios is the opposite of oligohydramnios. While oligohydramnios describes too little amniotic fluid, polyhydramnios describes too much. High levels of amniotic fluid often indicate the presence of swallowing or heart defects in the fetus. Polyhydramnios may also occur if the mother has diabetes, or if the fetus experiences an infection or gastrointestinal problems.
Symptoms of polyhydramnios include unusually quick uterine growth and abdominal discomfort. High levels of amniotic fluid can also cause premature uterine contractions.
Complications of High Levels of Amniotic Fluids
High levels of amniotic fluid increase the risk of umbilical cord prolapse. Umbilical cord prolapse occurs when the umbilical cord enters the birth canal before the baby's head. The cord can become tangled and both oxygen and blood flow to the fetus are restricted.
Polyhydramnios can also cause the amniotic fluid membrane to rupture, resulting in premature labor. Birth defects are associated with polyhydramnios, as are premature uterine contractions. During a pregnancy with high levels of amniotic fluid, the mother may experience breathing difficulties if the enlarged uterus pushes against the lungs.
Treatment for Polyhydramnios
Polyhydramnios treatment includes careful monitoring of the condition, with delivery as soon as the pregnancy comes to term. If necessary, amniotic fluid levels may be lowered with medication to decrease fetal urine output, or by means of amnioreduction, a process in which a needle is inserted through the uterus to drain amniotic fluid.
Amniotic Fluid Embolism
Amniotic fluid embolism is a rare complication of pregnancy. It occurs when amniotic fluid pass through the placenta into the mother's bloodstream. Once in the bloodstream, the amniotic fluid can travel to the lungs, where it causes breathing difficulties. In severe cases, an amniotic fluid embolism can cause death. Symptoms of an amniotic fluid embolism are similar to those for a pulmonary embolism.
Resources
Beers, M. H. & Berkow, R., eds. (1999). Normal pregnancy, labor, and delivery. The Merck Manual of Diagnosis and Therapy, 17th Edition. NJ: Merck Research Laboratories.
Callahan, T .L., Caughey, A. B., & Heffner, L. J. (2001). Blueprints in Obstetrics and Gynecology, 2nd Edition. MA: Blackwell Publishing.
Cincinnati Children's Hospital Medical Center. (updated 2004). Amniotic fluid problems/hydramnios/olighydramnios.
March of Dimes Birth Defects Foundation. (2002). Amniotic fluid abnormalities.
Pregnancy