Is Having Too Much Amniotic Fluid a Cause for Concern?

Amniotic fluid plays a crucial role in the development of a fetus. It cushions and protects the fetus from external pressures, blows, and harm. It also regulates body temperature and helps develop your baby's lungs, muscles, bones, and digestive system. In most cases, amniotic fluid is protective, but there is such a thing as too much of a good thing.

Read on to learn about the symptoms, causes, diagnosis, and treatment of polyhydramnios, a medical condition that's characterized by having too much amniotic fluid.

What Is Polyhydramnios?

Polyhydramnios is a condition characterized by having too much amniotic fluid in the amniotic sac surrounding a fetus during pregnancy. Research shows polyhydramnios only occurs in about 0.2 to 2% of pregnancies. To be diagnosed with this condition, you must have over 25 centimeters of amniotic fluid or a deep verticle pocket greater than 8 centimeters.

Normal amniotic fluid levels are between 8 and 24 centimeters. The range, however, depends on how far along you are, as the fluid levels increase as your pregnancy progresses. The fluid is highest around 34 weeks gestation.

Symptoms of Too Much Amniotic Fluid

Symptoms of polyhydramnios include:

• Breathing discomfort
• Preterm labor
• Premature rupture of membranes (PROM)
• Abnormal fetal presentation
• Cord prolapse
• Postpartum hemorrhage

You may also notice your belly getting larger more quickly than expected. "Typically, the patient will feel or look bigger than they think they should for their gestational age and may have more contractions related to uterine distension," says Lulu Zhao, MD, FACOG, FASAM, a board-certified OB-GYN and assistant professor at Case Western Reserve School of Medicine in Cleveland.

Dr. Zhao says that sometimes health care providers might suspect too much fluid if your fundal height is larger than expected or excess fluid is picked up on ultrasound.

Diagnosing Too Much Amniotic Fluid

If a health care provider suspects you have polyhydramnios, they will likely order some tests. This is to determine if you have too much amniotic fluid and, if so, if the excess amount of amniotic fluid is cause for concern.

An ultrasound is used to detect polyhydramnios, which is painless, noninvasive, and safe for you and your fetus. During the exam, a health care provider uses the amniotic fluid index (AFI) to measure the total amount of fluid in four different areas of the uterus. Alternatively, they may measure the deepest pocket of fluid within the uterus.

Polyhydramnios is diagnosed when measurements exceed 8 centimeters for a single deepest pocket of fluid or an AFI greater than 24 centimeters.

Causes of Too Much Amniotic Fluid

Polyhydramnios can occur when a fetus doesn't swallow and absorb amniotic fluid in expected amounts. The following health conditions may cause too much amniotic fluid:

• Gastrointestinal disorders
• Brain and nervous system problems
• Achondroplasia (a disorder that causes dwarfism)
• Beckwith-Wiedemann syndrome (a growth disorder causing a large body size)
• Poorly controlled diabetes in the gestational parent
• Lung disorders
• Multiple pregnancies
• Hydrops fetalis (too much amniotic fluid caused by Rh incompatibility)

According to the Society for Maternal-Fetal Medicine (SMFM), the two most common causes are maternal diabetes and fetal anomalies. Sometimes there is no apparent cause.

Effects of Too Much Amniotic Fluid

Dr. Zhao's biggest concern with too much amniotic fluid is an undiagnosed fetal anomaly or undiagnosed diabetes. She says excess fluid can also increase the risk for:

• Postpartum hemorrhage
• Unstable fetal lie (like going from head down to breech and back and forth, even during labor before rupture of membranes)
• Preterm uterine contractions
• Preterm birth
  

Usually, the condition doesn't cause much trouble, and most people with polyhydramnios will not have any significant problems. That said, too much amniotic fluid is associated with some risks.

Stillbirth

Polyhydramnios has an increased risk of stillbirth, and while the risk is double that of normal pregnancies, it's still a minimal risk. To put it into perspective, in pregnancies involving normal amniotic fluid levels, 2 out of 1,000 babies are stillborn; with polyhydramnios, it's 4 out of 1,000.

Preterm labor

As previously mentioned, most pregnant people will carry their fetus to term (and go on to deliver a healthy baby). That said, polyhydramnios does increase the risk of premature rupture of membranes and preterm labor.

Labor complications

Another possible complication involves labor itself. One study found that those with too much amniotic fluid had an increased risk of the following:

• Amniotomy (procedure to break the bag of water)
• Abnormal presentations (like the forehead and face rather than the back of the head)
• Labor induction
• Cesarean section (C-section)

In addition, research has found that umbilical cord prolapse (when the umbilical cord slips out before the fetus) is more likely to occur with too much amniotic fluid when an amniotomy is performed.

Research has also found that too much amniotic fluid is a risk factor for placental abruption, which means the placenta could separate before the baby is born. This poses an increased risk of postpartum hemorrhage.

While these all sound scary, and they're all possible with polyhydramnios, they're also very unlikely. That's especially true if you're close to term, your amniotic fluid is still near normal range, and you're being cared for by a trained health care team.

Treatment for Too Much Amniotic Fluid

Often, you won't need any treatment for having too much amniotic fluid. A health care provider will instead monitor your pregnancy and fluid levels closely. If your polyhydramnios has a known cause, like uncontrolled diabetes, for example, treatment will involve managing the underlying cause.

In some cases, health care providers will use amnioreduction, a procedure to remove some of your amniotic fluid. While widely used to manage twin-to-twin transfusion syndrome, research has found that this procedure can also be useful for managing the condition in singleton (non-multiple) pregnancies.

This procedure is done by inserting a needle into the uterus and sac to remove excess fluid. During the procedure, ultrasound helps guide the needle and monitor the fetus.

The Society for Maternal-Fetal Medicine only recommends amnioreduction in severe cases of polyhydramnios and recommends allowing labor to begin spontaneously for most mild cases when possible.