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Too much amniotic fluid: What causes polyhydramnios in pregnancy?

The condition occurs in roughly 1 to 2% of pregnancies.

When I was pregnant with my first child, I didn’t pop. I exploded. At 26 weeks, a well-meaning stranger asked if I had passed my due date. Passed my due date? I hadn’t even entered my third trimester. Shortly after, I was I was diagnosed with a condition called polyhydramnios.

What is Polyhydramnios

Polyhydramnios is the presence of excess amniotic fluid — the protective liquid that surrounds an unborn baby in the uterus during pregnancy. It occurs in roughly 1 to 2% of pregnancies, according to the Mayo Clinic.

It's typically seen in the second half of pregnancy.

How is it diagnosed?

If your uterus is measuring two or more weeks ahead of your expected due date, and your healthcare provider suspects polyhydramnios, they’ll order an ultrasound. If your amniotic fluid index (AFI) is greater than 24 centimeters, you have polyhydramnios. A normal AFI ranges from 5 to 24 centimeters.

“Polyhydramnios is classified as mild, moderate or severe,” David Colombo, division chief of maternal fetal medicine at Spectrum Health, told TODAY Parents. “We get more concerned the higher the number is.”

What causes polyhydramnios in pregnancy?

Polyhydramnios is often associated with gestational diabetes.

“When a mother’s blood sugar is high, she’ll pee more and then the baby will pee more,” Columbo said, noting that amniotic fluid after 20 weeks of pregnancy is mostly baby urine. (Yes, they drink their own urine!)

If gestational diabetes is ruled out, your doctor will look for other causes such as chromosomal abnormalities and obstructions.

“Children who have an obstruction between the mouth and the stomach will have extra fluid because they can’t drink and the fluid doesn’t get absorbed,” Colombo explained. “Sometimes structural abnormalities can cause polyhydramnios. New antibodies in the blood and viral infections can cause the fluid to be high. There’s really a whole list of things that we look for.”

Should I be worried about polyhydramnios?

The short answer is no, if you are being monitored by a health care professional.

“There is an increased risk for fetal demise. You’re also more likely to go into labor early,” Colombo said. “But we follow the fluid about every two weeks to see how high it’s getting.”

Colombo noted that women with polyhydramnios also undergo weekly or bi-weekly non-stress tests, which monitor the baby’s heart rate in response to its movements. If you have a severe case of polyhydramnios, your doctor might recommend delivering at 38 weeks gestation.

Bottom line: Remain calm and stay on top of your doctors appointments.

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