Polyhydramnios, or High Amniotic Fluid Levels: What's the risk? | Fit Pregnancy

High Amniotic Fluid During Your Third Trimester

Cause for worry, or not so much? Polyhydramnios (high fluid) is a rare condition, but here's what you need to know about it.


Thalia is 36 weeks pregnant and for the last few weeks, she’s been measuring large for dates. Her doctor sent her for an ultrasound, which revealed she has more amniotic fluid than some mothers do. A normal range of fluid at this stage of pregnancy is measured as between 5 and 25 centimeters or about 800-1000 mL. If the measurement is over 25, it’s called polyhydramnios and sometimes there are increased risks for mom and baby associated with that condition.

Thalia is measuring 24 centimeters of fluid, yet her doctor has already told her she has polyhydramnios and Thalia is scared.  

Essentially we have two questions here:
1. Does Thalia have polyhydramnios?
2. Is there something to worry about? 

Polyhydramnios only occurs in about 1% of pregnancies. Technically, Thalia isn’t in that 1% because 24 cm of amniotic fluid is still within normal range.  Will it go higher? Maybe. But it might also go lower. The important thing is that her doctor is keeping an eye on things. The bad thing is, her doctor has freaked Thalia out and she thinks bad things are happening to her and her baby. That makes me sad because, at this point, Thalia is normal. 

About 50 - 65% of the time, nobody knows what causes a woman to develop polyhydramnios.  The rest of the time, they can pinpoint it to one of  these conditions.

Conditions That Impact Polyhydraminos

  • Birth defects involving baby’s ability to swallow or kidney function. It’s baby’s ability to swallow and process fluid through the kidneys that regulates the amount of fluid in the uterus.
  • Diabetes – Some moms with diabetes might have increased levels of fluid.
  • Rh Incompatibility – A mismatch between Mom’s blood and baby’s blood.
  • Twin-to-twin transfusion syndrome (TTTS) – When one identical twin gets too much blood flow and the other gets too little.
  • Problems with the baby’s heart rate
  • An infection in the baby

Let’s rule a few things out for Thalia:

  • She didn’t mention twins so it’s not TTTS.
  • Her blood type was checked early in pregnancy and if she is RH negative, her doctor will give her a Rhogam shot to make sure she and her baby won’t have incompatibility problems.
  • She didn’t mention diabetes.
  • If there is a problem with baby’s heart rate it would most likely show up on ultrasound or monitoring. She didn’t mention that.
  • Could the baby have swallowing or kidney problems or infection?  It’s possible, but not likely.

Therefore, I’m guessing Thalia’s in the 50-65% for whom there’s no specific reason why she might have extra fluid. Keep reading to learn about the risks of this condition.


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