Amniotic fluid is the fluid that surrounds the fetus in the uterus. The fluid and fetus are contained in membranes called the amniotic sac. Problems with amniotic fluid include
Too much amniotic fluid for the length of the pregnancy
Too little amniotic fluid for the length of the pregnancy
Infection of the fluid, amniotic sac, and/or placenta (called an intraamniotic infection)
Pregnancy complications, such as too much or too little amniotic fluid, are problems that occur only during pregnancy. They may affect the woman, the fetus, or both and may occur at different times during the pregnancy. However, most pregnancy complications can be effectively treated.
Too much amniotic fluid
Too much amniotic fluid (polyhydramnios or hydramnios) stretches the uterus and puts pressure on the diaphragm of pregnant women.
Too much fluid may accumulate because of the following:
Birth defects in the fetus, especially a blockage in the esophagus or urinary tract
More than one fetus (multiple births)
Diabetes in the pregnant woman
Anemia in the fetus, such as that caused by Rh antibodies to the fetus’s blood produced by the pregnant woman (Rh incompatibility)
Other disorders in the fetus, such as infections or a genetic disorder
However, almost half the time, the cause is unknown.
Too much amniotic fluid can lead to several problems:
Labor may begin early—before 37 weeks of pregnancy (preterm labor).
The membranes around the fetus may rupture too soon (called premature rupture of the membranes).
The fetus may be in an abnormal position or presentation, sometimes requiring cesarean delivery.
The woman may have severe breathing problems.
The umbilical cord may come out of the vagina before the baby (called a prolapsed umbilical cord).
The uterus become stretched out and not be able to contract normally (a condition called uterine atony).
The woman may have bleeding from the vagina after delivery.
The fetus may die.
If premature rupture of the membranes occurs, the placenta may detach from the wall of the uterus too soon (called placental abruption).
Too little amniotic fluid
There tends to be too little amniotic fluid in the following situations:
The placenta and uterus are not functioning normally because the woman has a disorder, such as high blood pressure or placental abruption (premature detachment of the placenta), possibly resulting in the fetus not growing as much as expected.
The membranes around the fetus rupture too soon (called premature rupture of the membranes) or near the due date.
Pregnancy lasts 42 weeks or more (postterm pregnancy).
The fetus has a chromosome abnormality.
The fetus has birth defects in the urinary tract, particularly in the kidneys.
The fetus has not grown as much as expected (called intrauterine growth restriction).
The fetus has died.
In many cases, the cause is unknown.
Too little amniotic fluid (oligohydramnios) can also cause problems, such as the following:
The fetus may die.
The fetus may not grow as much as expected.
If the amount of fluid is greatly reduced, the fetus may be compressed, resulting in deformities in the limbs, a flattened nose, a recessed chin, and other problems.
The fetus's lungs may not mature normally. (The combination of immature lungs and deformities is called Potter syndrome.)
The fetus may not be able to tolerate labor, making cesarean delivery necessary.
Symptoms of Amniotic Fluid Problems
Usually, having too much or too little amniotic fluid does not cause symptoms in the woman. The woman may sense that the fetus is not moving as much as earlier in the pregnancy. Sometimes, when the amount of excess amniotic fluid is large, women have difficulty breathing or painful contractions before their due date.
Disorders causing or contributing to too much or too little amniotic fluid may cause symptoms.
Diagnosis of Amniotic Fluid Problems
A doctor's evaluation
Ultrasonography
Tests to identify the cause
Doctors may suspect too much or too little amniotic fluid when the uterus is too large or too small for the length of the pregnancy or when the fetus is not moving as much as expected.
Sometimes the problem is incidentally detected during ultrasonography. If a problem is detected, doctors can use ultrasonography to determine how much amniotic fluid is present.
If doctors detect too much or too little amniotic fluid, they check for a possible cause. For example, they may examine the vagina and cervix to determine whether the membranes around the fetus have ruptured too soon.
Blood tests may be done to check for disorders that can affect amniotic fluid (such as infections or diabetes). Ultrasonography and other tests (possibly amniocentesis) may be done to check for birth defects and genetic abnormalities in the fetus.
Treatment of Amniotic Fluid Problems
Ultrasonography to monitor the fetus's growth and to measure amniotic fluid levels
Monitoring of the fetus's heart rate
Treatment of any underlying disorders
Sometimes removal of amniotic fluid
Delivery
Ultrasonography is done regularly to monitor how much the fetus is growing and to measure the amniotic fluid levels. The fetus’s heart rate is also regularly monitored when the fetus is lying still and as it moves. This test is done to check on the fetus's well-being (called nonstress testing).
Any underlying disorders, such as diabetes and high blood pressure, are treated.
When there is too much amniotic fluid, doctors rarely remove the excess fluid. However, the amniotic fluid can be removed with a needle through the woman's abdomen when
Labor begins early.
The mother is having severe problems.
When there is too much amniotic fluid, doctors plan to deliver the baby at about 39 weeks in certain cases.
When there is too little amniotic fluid, most experts may recommend delivery between 36 and 37 weeks depending on how the fetus is doing.
