What is Amniotic Fluid?

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  • Written By: Mary McMahon
  • Edited By: O. Wallace
  • Last Modified Date: 27 September 2019
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Amniotic fluid is a fluid which surrounds a developing embryo to provide nutrition, insulate the embryo from shock, and encourage healthy fetal development. Humans are often familiar with it as a symptom of labor, because the membranes which hold the fluid back usually rupture in labor, in a phenomenon which people refer to as “breaking water.” When a woman's water breaks, it means that the baby is well on the way.

12 days after conception, the amniotic sac, also known as the amnion, starts to form. This sac protects the developing fetus, and it slowly fills with amniotic fluid and swells as the fetus grows. Initially, the mother's body provides the source of liquid, but over time, much of the fluid is fetal in origin. By the end of the pregnancy, a lot of the fluid is in fact urine generated by the developing fetus.

In the early stages, the amniotic fluid is clear, and it provides critical nutrition to the fetus as it develops. Over time, it fills with shed skin cells from the fetus, along with floating stem cells. These cells can be extracted in an amniocentesis to get information about the developing fetus. By the 34th week of pregnancy, the amniotic fluid has reached its peak level, and it will start to decline in the last weeks of the pregnancy.


This liquid is similar to seawater in terms of chemical composition, and it plays a number of important roles. In the second trimester, the developing fetus drinks and breathes the amniotic fluid, with the fluid contributing to the development of healthy lungs and a digestive tract. The fluid also gives the fetus room to move around, allowing her or him to develop a healthy skeleton and strong muscles. As an interesting side note, fluids conduct sound very well, so the fluid acts like a giant amplifier, allowing the developing fetus to hear the sounds of his or her mother's body along with the outside world.

Two disorders involve amniotic fluid. In oligohydramnios, there is not enough fluid, and the fetus can develop a variety of developmental problems, including clubbed feet. In Polyhydramnios, there is too much fluid. These conditions are generally diagnosed with the use of an ultrasound, and the prognosis varies, depending on the circumstances. As a general rule, either condition merits close attention so that problems with the fetus can be identified and addressed early.


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Post 5

I knew nothing much about this subject until my wife experienced increased amniotic fluid in her third trimester. As it was our first baby we were ultra cautious about everything, and her symptoms didn't match anything that was happening to other women in her pre-natal group.

Watch out for swelling in the ankles and feet, being short of breath, having a much bigger bump than usual for that stage and a general feeling of discomfort in the stomach area. These are all key symptoms, and require immediate medical attention.

My wife tested negative for pregnancy diabetes and the ultrasound showed just one baby rather than twins, both of which are common causes of excessive amniotic fluid. So all

in all the reason for this condition remained a mystery.

She did get incredible health care and a lot of monitoring, which led to the safe delivery of a beautiful child without a C-section. Subsequent pregnancies have been trouble free, which is a relief. The human body is such a wonderful thing, and I will never take any part of the baby making miracle for granted again.

Post 4

One thing that my doctors were worried about as I got further into my pregnancy was what appeared to be low amniotic fluid.

I had to go to the doctor once a week and have several ultrasounds done over the last few months, far before you typically have to start the once a week visits.

Apparently, they had found some amniotic fluid in one of the pap’s they had done. Ultrasounds revealed that there was not as much fluid as was normally needed.

However, I ended up carrying my baby girl to full term and everything was fine. There had been some talk of inducement or even a C-section though. Those options just never became necessary, and thank goodness for it.

Post 3

You hear about amniotic fluid, and all sorts of other wonderful bodily fluids whenever you get pregnant. The truth is, though, that I don’t think anyone can prepare you for all of the fluid that is there.

I was carrying my first child (I think I was maybe five or six months at the most) when I felt this warmth going down my legs. There wasn’t a whole lot of liquid, but I had no idea if this was bad or not.

I checked – it didn’t smell like pee and it certainly didn’t look like blood. It was just clear and smelled sweet.

I went immediately to my doctor because I completely panicked. (It had taken us

almost four years to get pregnant, and I was terrified something was going to go wrong.)

It was indeed a tiny amount of amniotic fluid, but the leak seemed to have been nothing to worry over.

I actually carried my daughter two weeks longer than the typical 40 weeks.

Then, when they broke my water and all of that fluid gushed out, I realized that a tiny bit of leaking didn’t hurt a thing. Heck, maybe I just had high amniotic fluid at the time of the leakage.

Post 2

@SailorJerry - first of all, relax! There's almost certainly nothing wrong at all. If your wife had a significant leak, she would probably be leaving puddles. (At any rate, she would be changing her underwear every half hour.) Amniotic fluid also has a distinct smell.

But her doctor or midwife could say for sure. Sometimes they find a leak when they do an ultrasound and notice low amniotic fluid; they also have little test strips that they use to check a discharge and see if it's amniotic fluid.

You don't say exactly how far along she is or when her next appointment is--there's a big difference between 29 weeks and 37! If she is far along and leaking fluid, they may want to induce labor, which can be problematic. If her next appointment is soon, I would just mention it to the provider then and get checked.

Post 1

How do you know if you're leaking amniotic fluid? My wife is in her third trimester and has had a lot of thin, watery discharge. How can we tell if we should be worried or not? She says that she thinks it's just cervical fluid and that an increase in cervical fluid is normal during the last trimester, but I can't help but worry.

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