Polyhydramnios (Excessive Amniotic Fluid)

Amniotic fluid is produced in a fetus’s kidneys, and it is expelled when a baby urinates while in utero. The baby then swallows some of the fluid. The rest remains in the womb, where it is useful for the following reasons:

• Provides cushioning/protection for the growing infant
• Allows the infant to move about in the womb, which helps with bone and muscle growth
• Promotes lung development
• Regulates temperature in the womb (2)

Polyhydramnios, an excess of amniotic fluid, occurs in about 1% of pregnancies. It is the opposite of oligohydramnios, a condition in which there is an insufficient level of amniotic fluid. Some of the most common causes of polyhydramnios are as follows:

• Maternal diabetes: Diabetes, including gestational diabetes, can lead to amniotic fluid build up.
• Congenital anomalies: There are certain genetic defects that prevent a baby from swallowing sufficient amounts of amniotic fluid.
• Twin to twin transfusion syndrome (TTTS): In some twin pregnancies, blood from one twin goes to the other. This can result in polyhydramnios and medical problems for both twins.
• Incompatible blood types: When a mother has an Rh-negative blood type and a baby has Rh-positive blood, this can cause the baby to develop a type of anemia, which can, in turn, lead to polyhydramnios.
• Fetal heart conditions: This could include a congenital defect, fetal arrhythmia, etc (3).

Some of the most common complications and symptoms associated with polyhydramnios include:

• Maternal breathing difficulties
• Preterm labor
• Premature rupture of membranes (PROM)
• Unusual fetal presentation
• Umbilical cord prolapse
• Postpartum hemorrhage (1)
• Placental abruption (3)

Because polyhydramnios is often caused by gestational diabetes, it may also be associated with macrosomia (a condition in which the baby is large for gestational age).

Polyhydramnios can be diagnosed based on the appearance of an ultrasound. If medical professionals suspect polyhydramnios, they may also perform the following tests:

• Amniocentesis: This is a way of sampling amniotic fluid to test for genetic conditions that may contribute to polyhydramnios.
• Doppler ultrasound: This is a type of ultrasound that can take images of the fetus’s circulatory system.
• Glucose challenge test: This test is for women with diabetes.
• Non-stress test: This is a means of checking for abnormalities in the fetal heart rate (3).

Mild cases of polyhydramnios may not require treatment, but doctors should have their patients come in for extra prenatal checkups to monitor the condition and make sure it does not become severe. Treatments for more severe forms of polyhydramnios sometimes focus on addressing the underlying cause(s). Additional treatments/interventions include:

• Amnioreduction: This involves using a long needle to drain excess amniotic fluid from the uterus. There are certain risks associated with this, which doctors must weigh when deciding whether it is an appropriate intervention.
• Medications to reduce the amount of fetal urine: This can put the fetus’s heart health at risk, so again, doctors must be careful in determining whether this is the right path. They must also carefully monitor the baby for signs of fetal distress.
• Early induction
• Bed rest: This can help delay preterm labor in cases of moderate polyhydramnios (3).