Amniotic Sac? Bag of Waters? It’s Plural?
The human body is a fascinating thing. Not only do we have the capacity to grow another human being, we also grow the system to do so. This system includes the placenta, umbilical cord, amniotic sac, and amniotic fluid.
The amniotic sac consists of two parts.
The inner part that surrounds the amniotic cavity, including the baby and amniotic fluid, is called the amnion. The outer portion, which is attached to the placenta, is called the chorion. They are hard to differentiate, but are two separate membranes.
Amniotic fluid serves many purposes for the growing baby:
- It allows them to move and develop their muscles
- It provides a cushion for any impact on the stomach
- It regulates the temperature of their environment
It is comprised mostly of water, fetal waste (urine), and fetal skin cells. The amount of fluid increases throughout pregnancy and at term stands at approximately 1 liter.
By 42 weeks, the levels have started to decrease. A biophysical profile can give a measure of where the fluid levels stand, especially in post-dates pregnancies.
Birthing people often have a hard time determining whether leakage is amniotic fluid or urine.
As a doula, one of the most common questions you’ll answer is “did I just pee or did my water break!?”
There are a few ways to determine if it is amniotic fluid or urine. The client can urinate and then lay down for 15-20 minutes, when they stand up, if fluid gushes out again, it is likely to be amniotic fluid.
One of the most definitive ways to tell if the amniotic sac is ruptured or leaking is a pH test which can be done at the birth facility or provider’s office. The pH of amniotic fluid is between 7.0 and 7.5, while the pH of the upper vagina is 3.8 to 4.5. A pH of over 4.5 indicates the presence of amniotic fluid.
So why is waters plural?
The amniotic fluid is generally divided into forewaters and hind waters. The forewaters are in front of the baby’s head (between the baby’s head and the opening of the cervix) and the hind waters are behind it. When the amniotic sac is ruptured, the forwaters will come through the cervix, but the baby’s head will likely block the remainder of the hind waters. This is why many providers will wear eye covers during delivery.
There’s no telling where that water will splash!
The forewater, still in the amniotic sac, can bulge down into the cervix.
Amniotic fluid levels in general can lessen the pressure on the placenta, umbilical cord, and the baby during intense contractions, and can help lessen heart decels in the baby by keeping the cord from being compressed.
Television and movies would have us believe that every woman’s labor begins with an ocean of water suddenly pouring out of her vagina followed by, intense contractions that make husbands jump in the car, forget their wives and suitcases, and you know the rest!
The reality is a bit less sensational. Less than 15% of birthing people have their “waters break” as the first sign of labor. As doulas, our clients have the comfort of knowing they have someone to call and say “I might have just peed on myself” and receive support, guidance and education without all the giggling.