What happens to the cervix during labor and childbirth?

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I have never been and likely will never be pregnant, but I’m unclear on how the cervix can dilate to 10 cm.

I always assumed the os (the small opening in the cervix) is what dilates and what the baby passes through. But that seems physiologically impossible, given that a normal cervix is only about 2.5 cm across.

I know that “effacement” is also something that happens, but I don’t know how that relates to dilation. Can someone please walk me through it? Thanks!

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6 Answers

Anonymous 0 Comments

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Anonymous 0 Comments

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Anonymous 0 Comments

NAD, but a dad.

The cervix is a little bit like the muscular ring (sphincter) which helps hold your stomach contents in (both up and downstream), and so has the ability to relax and open. The “birthing” hormones cause it to do exactly that, opening up far larger than one would expect to be possible given the original “resting” inner and outer diameters of the structure itself. Note that it isn’t exactly a muscular structure, and is actually being PULLED open by other structures, but the metaphor still roughly works. Kinda.

This stretching isn’t exactly comfortable for the woman, and given that a baby’s head is irregularly shaped (to say nothing of the shoulders) even 10cm isn’t exactly the right size, in and of itself, so in the birthing process it often gets even MORE stretched and distorted. But as with a LOT of tissues in the human body stretching and contortion is surprisingly possible. A patch of skin can stretch by nearly 50% larger than the original patch, muscles can regularly be more than double their “contracted” length, the tissue holding your various organs in place is INCREDIBLY stretchy, even bones have a surprising amount of flex if they are healthy.

Anonymous 0 Comments

[removed]

Anonymous 0 Comments

NAD, but a dad.

The cervix is a little bit like the muscular ring (sphincter) which helps hold your stomach contents in (both up and downstream), and so has the ability to relax and open. The “birthing” hormones cause it to do exactly that, opening up far larger than one would expect to be possible given the original “resting” inner and outer diameters of the structure itself. Note that it isn’t exactly a muscular structure, and is actually being PULLED open by other structures, but the metaphor still roughly works. Kinda.

This stretching isn’t exactly comfortable for the woman, and given that a baby’s head is irregularly shaped (to say nothing of the shoulders) even 10cm isn’t exactly the right size, in and of itself, so in the birthing process it often gets even MORE stretched and distorted. But as with a LOT of tissues in the human body stretching and contortion is surprisingly possible. A patch of skin can stretch by nearly 50% larger than the original patch, muscles can regularly be more than double their “contracted” length, the tissue holding your various organs in place is INCREDIBLY stretchy, even bones have a surprising amount of flex if they are healthy.

Anonymous 0 Comments

NAD, but a dad.

The cervix is a little bit like the muscular ring (sphincter) which helps hold your stomach contents in (both up and downstream), and so has the ability to relax and open. The “birthing” hormones cause it to do exactly that, opening up far larger than one would expect to be possible given the original “resting” inner and outer diameters of the structure itself. Note that it isn’t exactly a muscular structure, and is actually being PULLED open by other structures, but the metaphor still roughly works. Kinda.

This stretching isn’t exactly comfortable for the woman, and given that a baby’s head is irregularly shaped (to say nothing of the shoulders) even 10cm isn’t exactly the right size, in and of itself, so in the birthing process it often gets even MORE stretched and distorted. But as with a LOT of tissues in the human body stretching and contortion is surprisingly possible. A patch of skin can stretch by nearly 50% larger than the original patch, muscles can regularly be more than double their “contracted” length, the tissue holding your various organs in place is INCREDIBLY stretchy, even bones have a surprising amount of flex if they are healthy.