They can't feel your placenta from the outside therefore can not measure from the pelvic bone to placenta. The fundus is the top of your uterus and that is what they feel for when they measure you. Depending on how high the top of your uterus is says if you and baby are growing on schedule.
Like geek mom and AML said your placenta could be anywhere in your uterus. It's from the public bone to the top of the fundus. (Your uterus) and like AML said it's to match up your weeks vs height (your fundal measurement)
Well from all my appointment its been from where the placenta is and down the pubic bone
It's actually a measurement from the pubic bone to the fundus... not the placenta (which could be anywhere in the uterus!!) And AML got it exactly right as to why.
It's from your placenta down to your pubic bone. And it does kind of meansure out your weeks but sees how your measuring in size. As if your bigger than your meant to be it could be you have a big baby or diabetes
Woops, I think I originally read your question incorrectly... pregnancy brain! Lol
It's the other way around - they don't use that measurement as a way to see how far along you are, they measure you to make sure your uterine growth matches how many weeks you are. They know how far along you are after performing an ultrasound.
Seems like my dr is all dowm in my vagina jeesh lol