I am a scientist...I understand probability and statistics. But when it comes to a doctor trying to estimate the size of a baby in utero, I honestly think they're just guessing. Worse than that, maybe they're just makin' stuff up.
They say there's a method...number of centimeters of uterus translates loosely to number of weeks gestation. So when I measured at 29 weeks when I was actually 31 weeks along, they noted it on my chart. Then two weeks later, I had only progressed one week, and was now officially "behind". The doctor made another note, this one more ominous...I had to schedule an ultrasound to make sure the baby was growing correctly. The two options, she said, were that the baby was small, or in the transverse position (side to side instead of head down). "Was your first baby small?", she asked, hopefully. "Eight pounds eleven ounces," I answered. "Oh," she said, and made another note.
So I was not really worried, per se, I was more like, well, insulted. A small baby? Me? Small had somehow translated to "not perfect." If it was perfect, I wouldn't need an ultrasound, right? Well, we had the ultrasound on Wednesday, and the baby is NOT small. The baby is HUGE. According to the skull, abdomen, and femur, it's measuring at 37 weeks plus, when I'm just over 34. We got to see its beautiful face, chubby cheeks, and got to hear its PERFECT heartbeat...which, by the way, is on the low side. The old wive's tale that predicts the sex based on heartrate says that's a boy, as does the way I'm carrying.
On December 20th, at 7:30 in the morning, when they pull this baby out of my belly, I will not be surprised when they hand me a perfectly average sized girl. Hocus pocus, probablility, voodoo, whatever. Just remember, it's not over til it's over.