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)
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 (hemolytic disease of the fetus and newborn)
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:
Preterm labor and possibly prelabor rupture of membranes (sometimes followed by placental abruption) or preterm labor
Fetal abnormal position or presentation, sometimes requiring cesarean delivery.
Severe breathing problems in the woman
Umbilical cord prolapse: Umbilical cord may come out of the uterus before the baby
Uterine atony: Uterus become stretched out and not be able to contract normally
Postpartum hemorrhage: Bleeding from the vagina after delivery
Fetal death
Too little amniotic fluid
Causes of too little amniotic fluid include the following:
Uteroplacental insufficiency: Placenta and uterus 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
Some medications
Rupture of membranes before or near the due date
Postterm pregnancy: Pregnancy lasts 42 weeks or more
Chromosome abnormality of the fetus
Birth defects in the urinary tract, particularly in the kidneys
Intrauterine growth restriction: Fetus has not grown as much as expected
Fetal death
In many cases, the cause is unknown.
Too little amniotic fluid (oligohydramnios) can also cause problems, such as the following:
Intrauterine growth restriction: Fetus has not grown as much as expected
Limb and facial deformities (if the amount of fluid is greatly reduced and begins early in the pregnancy)
Delayed or incomplete lung maturation
Inability of the fetus to tolerate labor, leading to the need for cesarean delivery
Fetal death
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 amniotic fluid is excessive, 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 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.
