Beyond keeping your baby at a constant, cozy temperature and offering a layer of cushion and protection, amniotic fluid is a critical ingredient to any healthy pregnancy. Beginning in your second trimester, your baby will begin swallowing and tasting the amniotic fluid in your womb and even take "practice breaths" to start preparing his lungs for the outside world.
Sometimes, however, the body produces too much amniotic fluid — a condition known as polyhydramnios. Although polyhydramnios is usually mild and resolves on its own, it can sometimes lead to pregnancy complications.
What is polyhydramnios?
Polyhydramnios (also known as hydramnios) is a pregnancy condition where there's too much amniotic fluid surrounding a baby in the uterus.[1] This extra amniotic fluid tends to slowly build up during the second half of pregnancy.
Most cases of polyhydramnios are mild, due to a temporary shift in amniotic fluid production. This slight bit of extra amniotic fluid usually goes away on its own without any treatment.
In the rare cases when fluid accumulation is severe, it could signal a problem with the baby, such as a central nervous system issue, gastrointestinal defect or inability to swallow. Consistently high levels of amniotic fluid can put your pregnancy at risk for premature rupture of the membranes, premature labor, placental abruption, breech presentation or umbilical cord prolapse.
What causes polyhydramnios?
In about half of cases, polyhydramnios has no known cause. In the other half, polyhydramnios may be caused by:
- Birth defects that affect swallowing (which helps regulate amniotic fluid levels)
- Uncontrolled maternal diabetes (high blood glucose levels can cause the baby to pee more often)
- An abnormal fetal heart rate
- An infection in the baby
- Blood incompatibilities between mom and baby (like Rh and Kell diseases)
- Twin-to-twin transfusion syndrome
- Low red blood cell count in the baby (anemia)
What are the signs of polyhydramnios?
It's common to not experience any symptoms of polyhydramnios at all. If you do, signs of too much amniotic fluid may include:
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- Difficulty feeling fetal movements, due to the extra amniotic fluid cushioning your uterus
- Abdominal discomfort and trouble breathing, since the uterus presses on your lungs and other organs
- Uterine contractions, indigestion, constipation, swelling in the leg, hip, ankle and/or foot and breathlessness (symptoms that are common during any healthy pregnancy)
- Peeing less often
Because polyhydramnios tends to cause few symptoms, it's usually detected during a prenatal exam, when your fundal height — the distance from your pubic bone to the top of your uterus — is larger than expected.[2]
Polyhydramnios is diagnosed using an ultrasound, which measures the amount of fluid in the amniotic sac. If you have too much amniotic fluid, your practitioner may sometimes suggest additional tests, including amniocentesis (to check for possible chromosomal abnormalities) and blood work.
How common is polyhydramnios?
Polyhydramnios occurs in roughly 1 to 2 percent of all pregnancies.[3]
Who is most at risk for polyhydramnios?
Known risk factors for too much amniotic fluid include having uncontrolled diabetes and carrying multiples. However, in some cases there is no known cause.
What you should do if you have polyhydramnios during pregnancy
Most cases of polyhydramnios come and go, and the extra fluid reabsorbs on its own. So unless fluid accumulation is fairly severe, there's nothing you need to do. Just keep going to your scheduled prenatal appointments with your practitioner, who will keep an eye on you with additional ultrasounds and possibly a nonstress test or biophysical profile.
In more severe cases of polyhydramnios, your practitioner may suggest a procedure called therapeutic amniocentesis, where fluid is removed from the amniotic sac using a needle. He or she may also prescribe a medication to help lower the amount of urine your baby makes, which in turn helps to reduce the amount of amniotic fluid. Some practitioners may also recommend delivery at 39 weeks for severe polyhydramnios.
Because severe and persistent polyhydramnios is linked to an increased risk of premature rupture of the membranes, be sure to call your practitioner immediately if your water breaks on its own before labor. It can put you at an increased risk of infection.
Polyhydramnios can also affect your baby's position (making a breech delivery more likely), and the extra fluid can raise the risk of cord prolapse.
If you have polyhydramnios near your due date, your doctor will recommend that you give birth in a hospital and may recommend an induction or planned cesarean section.
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