And she thinks she is big now!

Here's a curiosity: the measurement in centimetres that the midwife takes of the uterus matches the number of weeks' gestation. PP is 36cm right now, ie 36 weeks.

Putting aside the obvious difficulties (how did it work before metrication? if a non-pregnant woman has a 10 cm uterus is she permanently 10 weeks pregnant?), there's a satisfying cubic function at work here. Assuming the measurement is a chord on a sphere, and if we know the radius (tummy-button to spine) and the angle (around 90 degrees), it is possible to work out the weight gain between now (36cm) and 40 weeks (ie, 40cm) if her density is about 0.9 (when compared with water).

With me so far? Good.

Since my density is waaaaay above 1.0, I'm not about to attempt to work this out. The summary is: she is going to grow much, and I mean *MUCH*, bigger.

It's all to do with linear vs volumetric. As a quick glance through On being the right size by J B S Haldane will tell you, a 36 to 40 linear increase is slightly less than 10%; the same figures give a volume increase of about 23% .

And she thinks she is big now!

"On being the right size," found at http://irl.cs.ucla.edu/papers/right-size.html

On being the right size

Apparently Toblet is now about twelve ounces. One and a half packs of butter. If he or she hits a fairly standard eight pounds at birth, that's a staggering ten-fold increase in weight in the next 20 weeks. (In new money, 360g becomes 3.6kg)

I weigh 200lb (91kg); the comparative growth rate would be reaching slightly less than a ton (910kg) in twenty weeks, adding an average of 90lb (41kg) a week. The world's heaviest person, Jon Brower Minnoch, weighed in at a feeble 1,400lb (635kg).

Pic of Jon Brower Minnoch from http://www.dimensionsmagazine.com/dimtext/kjn/people/heaviest.htm There's something on the web for everyone, I guess.

On being the right size

Depending on which book you read and how many weeks they count, Toblet is around 320g, covered in brown greasy goo to stop it shrinking in the wash, and growing fast.

I peeked ahead in one of the books. In ten weeks from now, 30 weeks, the baby will be more than three times heavier at over 1kg.

Unbelievable.

Try reading J B S Haldane, "On being the right size," found at http://irl.cs.ucla.edu/papers/right-size.html