At your average prenatal visit, your doctor will take a tape measure starting at your sternum, pull it over your belly to your pelvic bone (while you are laying down) and announce a resulting number as ‘you’re measuring 18 weeks). What she is actually announcing is the number of centimeters that measurement it – which just happens to roughly coincide with the number of weeks gestation a normal singleton pregnancy is. The purpose is to make sure that there is consistent growth – consider it your baby’s first growth chart for all practical purposes.
This method obviously has some limitations though! For instance, if your baby happens to have a generously filled amniotic sac, you might think you are having the Goliath of babies, only to find that instead, you have been growing more Olympic swimming pool inside you than baby mass. Let’s hope that means he’ll be a good swimmer!
With twins, the technique is only mildly useful. Obviously, you’ll be measuring larger than a singleton mom. So when you’re in for your 20 week appointment and your doctor announces ‘You’re measuring 24 weeks’, that simply means, ‘You’re belly is about as big as a singleton mom’s is at 24 weeks’. So yes, if you stay pregnant long enough, you too will have the joy of measuring 42 weeks, 45 weeks, or maybe even 50 weeks!
The challenge with using measurements as a growth indicator for M.O.M.s is this. As long as you are growing, you know that at least one of your babies must be growing, but you don’t know if they are BOTH growing. For that reason, there are typically more ultrasounds done for mothers of multiples than for singleton mothers.
Below are some of my measurements at various times in my first pregnancy. FYI – my babies were both 7 pounds when they were born, so this is approximately what one would measure with 2 very average-sized babies inside of her!
At 17 weeks, measuring 21 cm
At 19 weeks, measuring 23 cm
At 21 weeks, measuring 28 cm
At 23 weeks measuring 32 cm
At 26 weeks measuring 36 cm
At 27 weeks, measuring 37cm
At 30 weeks, measuring 41 cm
At 32 weeks measuring 40 cm (must have been off on one of these, or babies changed position)
At 34 weeks, measuring 46 cm
At 36 weeks, measuring 47 cm
At 37 weeks, measuring 49 cm
At 38 weeks, measuring 50 cm
That was the last measurement taken! I actually measured my girth...I have to double check the exact figure - but if memory serves, I think it was 50 inches! IKES!