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Watching your belly grow may be the most exciting part of pregnancy. Ever wonder what all is going on in there? Well, your girth expands from the increasing size of your baby (this one’s probably obvious) and the amniotic sac and fluid that surround your little one.

Your baby produces amniotic fluid in their lungs and kidneys. They then swallow the fluid and pass it out as urine. This waste is carried away by your placenta. But sometimes, this delicate balance of production, absorption, and excretion is upset and too much amniotic fluid builds up. Enter hydramnios.

Hydramnios, also known as polyhydramnios, is a condition where you have too much amniotic fluid.

The amount of this cushioning fluid gradually increases as your pregnancy progresses. Research shows that — in a typical pregnancy — at 12 weeks you’ll have about 35 milliliters (mL) of amniotic fluid. At the end of your pregnancy, you’ll be up to about 800 mL.

If you have hydramnios, your amniotic fluid may reach 2,000 mL or more at term. Research suggests that between 0.2 and 1.6 percent of pregnant women will have hydramnios.

Depending on the amount of extra amniotic fluid that builds up, hydramnios may be mild, moderate, or severe. If you have mild hydramnios, you won’t notice any symptoms.

With moderate hydramnios, the extra fluid may make it more difficult for you to feel your baby moving. You may also be uncomfortable and breathless because of the extra fluid pressing against your lungs and other parts.

Severe hydramnios may cause contractions.

If you’re carrying twins or more, it’s more likely that you’ll have hydramnios.

But according to one study, in about 40 percent of the cases of hydramnios, it’s impossible to pinpoint the cause of the extra fluid. You can put it down to just another quirk of pregnancy.

More severe cases of hydramnios could be caused by the pregnant person’s diabetes, a problem with the placenta, or the development of an unexpected condition in the baby. (These unexpected conditions can include genetic syndromes, infections, or immune responses.)

There are two ways to check for hydramnios: fundal height and ultrasound. A doctor can check your fundal height by measuring the distance from your pubic bone to the top of your uterus. By feeling your uterus and your growing baby through your belly, an experienced doctor can get a good idea of how you and your baby are faring.

Using ultrasound, a technician can measure the amount of amniotic fluid in your uterus. The simplest method involves dividing your uterus into four quadrants and then measuring vertically the volume of amniotic fluid in the deepest quadrant.

Mild hydramnios most likely won’t cause you any trouble and will simply resolve on its own — just like many of your other pregnancy-related symptoms. However, severe hydramnios can sometimes lead to pregnancy complications for both you and baby.

You may have:

  • breathing difficulty
  • urinary tract infections
  • premature rupture of membranes
  • a sudden loss of large amounts of amniotic fluid that could cause your placenta to detach
  • preterm labor
  • umbilical cord prolapse through the open cervix during labor
  • postpartum bleeding

Baby may:

You can’t prevent hydramnios. So if you suspect that you have symptoms, speak with your doctor so that you can be checked and receive treatment if necessary.

Treatment depends on severity. In mild cases of hydramnios, your doctor may choose to watch and wait. In moderate to severe cases, you may need a hospital stay — so stock up on your reading material. Your doctor may recommend testing or medication.

Testing may include the following:

  • monitoring your baby’s heart rate and any contractions you may have
  • blood tests to check for diabetes or an infection

Medication may include the following:

  • medication to prevent a preterm delivery
  • non-steroidal, anti-inflammatory drugs to reduce the amount of amniotic fluid
  • medication to reduce the amount of urine and lung liquid your baby produces

Your doctor may also recommend physical removal of the excess amniotic fluid. However, research shows that complications can occur in 1 to 3 percent of people who undergo this procedure.

If you have hydramnios, you’re most likely dealing with a little extra load to carry. If it’s more complicated than that, your doctor will recommend testing and treatment so that you can sail smoothly to the end.