How Does A Baby Actually Get Out?

Monday, July 2, 2018

If you’re currently growing a baby this is an unavoidable question. For most people the anatomy just doesn’t make sense. A real baby is going to go from the inside of your body to the outside of your body, hopefully through your vagina. I totally get why, without knowing some things, that could be confusing and worrisome. Here’s the thing. There’s a really good, and simple design at play. The process of Labor and delivery consists of three key actions. To understand them you just need to understand some basic anatomy.

Babies grow inside of a muscular organ called the uterus. The placenta, umbilical cord, and amniotic fluid also live in the uterus. Think about it like the garage attached to the main house that stores the baby and all of it’s things. The bottom of the uterus is called the cervix. Most people do not even think about the cervix ahead of pregnancy, so it’s ok if this is a new concept for you. I like to think about the cervix like the garage doors in our equation. Below the cervix is the birth canal or vagina. Think about that like the driveway. The last piece of the equation is the pelvis. You can feel this on your body by finding your front hip points, your pubic bone between your legs at the front, your tail bone in the crease of your bum, and your sitz bones underneath your seat when you are sitting well. Think about these boney points on the pelvis as the landscape outside of the garage (mailbox, garbage cans, plants etc). Their placement will determine how much room our car / baby has to turn into the driveway (or the vagina).

Given optimal conditions, birth consists of these three actions:

1\. the uterus contracting

2\. the cervix opening

3\. the baby’s rotation and descent

Most people have heard about uterine contractions, or rather, “contractions.” And most people have heard of “dilation” or at least know that something (maybe the vagina) has to open or stretch. Lesser known is the role of the baby in the labor process and more importantly the synergy between the three actions and its implication on the culture of labor and delivery.

There is a brilliant feedback loop between uterine contractions and cervical changes. When a baby presses down on the cervix, the pregnant body releases a hormone like substance (called prostaglandins) to help the cervix get a little thinner (effaced) and a little more open (dilated).

The release of those hormones sends a signal to your brain to make another hormone called oxytocin. Oxytocin causes the uterus to contract or squeeze really hard, from the top of the muscle. Because the tissue of the cervix is thinning out, and the cervix is connected to the uterus, as the uterus contracts, it pulls the cervix up and out of the way AND pushes baby down further on to the cervix. It’s a cycle! The pressure from the baby causes the release of prostaglandins and prostaglandins in turn cause the release of oxytocin so there are more contractions that can pull the cervix up and out of the way and continue to push the baby down and out. The garage doors open because they are being pulled up by the inner workings of the garage.

Childbirth is most often explained as the process of uterine contractions and cervical dilation. But the baby’s rotation and descent is a critical piece of the equation. If you look at the anatomy image above you can see that the cervical opening is not lined up with the vaginal opening. The image above shows a baby heading straight toward the tailbone. In order for the baby to get into the birth canal, it has to rotate its body and tuck its head under the pubic bone at the front of the pelvis. And in most cases, babies are pre-programed to do. In fact they have a series of moves we call the cardinal movements.

Imagine our car is leaving the garage, it needs to turn quickly in order to stay on the driveway. Granted there’s an art to getting a car from the driveway into road (it’s where the muscles of the pelvic floor come in) but honestly, that’s a different conversation - and NOT an essential action of childbirth.

The essential actions of childbirth, in order to get a baby born vaginally, the uterus contract (so, you’ll need oxytocin), the cervix has to dilate (so, you’ll need prostaglandins)) and baby has to rotate and descend.

We can assist or hinder our body’s ability to produce oxytocin and prostaglandins. We can assist or hinder our baby’s ability to rotate.

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