this might be a really stupid question. But does the sac move around your uterus or is it like anchored where it is and will just expand to fit your growing baby?

It's just because mine is really down low in my uterus, and lots to the left. When I find baby's heartbeat with my really rubbish monitor, it seems like baby moves away like he's going "okay, so now you've heard me, you know I'm fine, I've got better things to do...like swimming!"

Anyway, I was just wondering if anyone knew. I hope I don't sound incredibly stupid.

I honestly don't know for a fact, but I believe it's anchored. My Peanut does the same thing though, I've had to chase him around my uterus trying to 'lock in' on his HB. I think he figures once I've heard it for 5 seconds he's all good to go.

As your baby gets bigger, your uterus (amniotic sack) will grow and will move up to behind and above your belly button.

thanks PitbullMommy, I'm glad someone else has a bean who likes to let them hear what they want to hear then just swim away!

Holldoll, I don't think the uterus is the same as the amniotic sac. Uterus is just another word for womb. So yes, the uterus grows, and the amniotic sac (with baby inside) grows (and eventually takes up the space in your uterus) but I was wondering if the position that the amniotic sac takes in your uterus/womb changes or if it's root position remains the same. At least that's how I understand it.

I think it would be rooted to some extent because of the umbilical cord. That has to pass through the sac and to the uterin wall. Right?

Not exactly. The placenta is actually between the amniotic sac and the uterine wall.

But, there is a layer of tissue called the chorion that is between the placenta and the amniotic sac that the amniotic sac anchors to around 8 weeks gestation. Then as the baby grows (and amniotic sac) the surface of the amniotic sac will evenually fuse to the surface of the 'pregnant' uterine lining that is not placenta.

Similarly, the essence of a membrane sweep to kick start labor is that the healthcare professional inserts a finger into the soft cervix and seperate the membrane from the cervix. This should release prostaglandins which hopefully kick starts labor.

So the amniotic sac isn't just all 'floating' around in your uterus, it is (at times) partially or fully anchored to the uterine wall as the baby grows and the uterus grows (depending on how far along you are).

thank you all - especially to you Margerle as you've really cleared up the whole dynamics of it for me! It is funny how before I expect a lot of people find before they get pregnant they just don't think about it too much but now that I'm pregnant I want to know everything about human biology and reproduction!

I'm a biology junky