Anyone ever think or care about finding a way to estimate the volume of a belly? Any way to extrapolate from the waist measurements they do? To the eye, does a torpedo belly appear larger than it actually is from vs a vertically oriented belly? Waist measurement used as a scale to extrapolate volume using weight gain and density. This week it's 30 cubic inches and next week 32 cubic inches. Could you tell the difference between a 30 cubic inch belly vs. 35 cubic inch in different women? Height probably plays a role too. How would a belly growth graph per week look of a multiples mom vs singleton? Is one linear and the other exponential? Probably all BS, but just wondering if there is anything to how we actually perceive the way the bellies look vs actual size.

All very good thoughts. I've always been intrigued by belly measurements, but I was usually thinking in circumference. I have a separate folder on my computer of pictures and videos of women measuring their belly. Anything over 48" seems to be pretty massive, but it is interesting that sometimes measurements smaller than that also look huge. I think you are correct in thinking belly shape and a women's height has a factor in the appearance of hugeness.

Now if we could develop a standard way to measure belly volume, then travel all around measuring the biggest bellies every week or so to gather this info, that would be great. You know, for the science, right? We would need lots of pictures, videos, and other data to support this research too. If we are engaging in science we need to be thorough! I will volunteer to measure all the big bellies within a 100 mile range of me.

Sounds like a couple of engineers at work here...

Interesting question!

Quote:Any way to extrapolate from the waist measurements they do? To the eye, does a torpedo belly appear larger than it actually is from vs a vertically oriented belly? Waist measurement used as a scale to extrapolate volume using weight gain and density.

There is some correlation, obviously, but it's imperfect. The uterus grows in all directions, not just outward. Also, are you basing it off the entire waist measurement? If so, you're measuring things in the torso/stomach cavity/spinal area that aren't belly/uterus. To look for a true correlation you would need the woman's pre-pregnancy waist measurement, then subtract that from whatever method you use to compute her pregnant volume.

Quote:This week it's 30 cubic inches and next week 32 cubic inches.

You're way underestimating here. Keep in mind that a cubic inch is very small. A 3"x3"x3" cube is 27 cubic inches; a 4"x4"x4" cube is 64 cubic inches. Bellies obviously get a lot bigger than that.

Quote:Could you tell the difference between a 30 cubic inch belly vs. 35 cubic inch in different women?

Setting aside the facts from above re: inadequate estimates of size, the answer to your question is probably not. If we use the formula for volume of a sphere, which is the most convenient geometric shape to use:

volume = (4/3) * pi * r^3

and since we know the volume, we're solving for r:

r = ∛(volume * 3 / (4 * pi))

then a 30 cu.in. sphere...

r = ∛(30 * 3 / (4 * pi)) = 1.93

...would have a diameter of 3.86 inches.

A 35 cu.in. sphere...

r = ∛(35 * 3 / (4 * pi) = 2.03

...would have a diameter of 4.06 inches.

And since we know that the cross-section of a sphere at its widest point is a circle, and we know that the circumference of a circle is 2 * pi * r, the difference in circumference between the two would be only 0.63 inches.

We should also remember that the volume of a sphere increases faster than its radius/diameter. Going from 30 to 35 - a roughly 16% increase - only resulted in a 5% increase in diameter. Doubling the volume (for example, going from 35 cu.in. to 70 cu.in.) results in only a ~25% increase in diameter (in this case, just a 1.05 inch increase in diameter).

So now let's apply this to the real world as best we can. Let's take a pregnant woman with, say, a 45-inch waist. Let's use the calculations for circles and spheres, imperfect though they may be. The waist measurement is the circumference, so our radius is 45 / 2*pi, or 7.16 inches. The volume would be 1537 cubic inches. Now let's say she grows to a 46-inch waist; tl;dr, she adds 106 cu.in. just from one extra inch of circumference/waist. So you can see that the volume changes drastically with small changes in waist size. Conversely, small changes in volume result in negligible changes in waist size.

Now that I've vomited up all that hypothetical mathematical bullshit, let's talk about the fact that someone apparently did a study of this very thing over 30 years ago. They found that the average volume of a 40-week uterus was about 4500mL, which is about 274 cu.in.

Quote:How would a belly growth graph per week look of a multiples mom vs singleton? Is one linear and the other exponential?

It wouldn't be exponential, just a larger linear growth.

Quote:Anything over 48" seems to be pretty massive, but it is interesting that sometimes measurements smaller than that also look huge. I think you are correct in thinking belly shape and a women's height has a factor in the appearance of hugeness.

Yep, the proportionality of the belly to the rest of the body is definitely a factor. A 48-inch waist would look massive on a 5ft 100lb girl, but much less noticeable on a 5'6" 200lb girl. My wife is 4'11" and never got larger than about 43" in any of her pregnancies, yet she looked huge anyway.

The simple truth is that every woman carries differently. You'd expect short women to always carry large and tall women to always carry small, but throughout the years I've known plenty of counterexamples on both ends of the spectrum. Sometimes women even carry differently from one pregnancy to another. A former coworker's wife fit into the small and petite category and she got absolutely fucking massive with her first pregnancy (her belly was literally bigger than a beach ball), yet she was much smaller for each of her subsequent three pregnancies, despite all three of her other kids being larger/heavier at birth than her first.

I guess this is one reason why the only measurement OBs care about is the fundal height (vertical measurement of the uterus in centimeters). Maybe it is the only measurement that correlates most of the time.

Well, now I know the username DoubleIntegral isn't just chosen because it sounds cool :p

(May 30, 2018, 9:51 am)CutePikachu Well, now I know the username DoubleIntegral isn't just chosen because it sounds cool :p

You may be the first person to ever think it sounds cool.