The baby's size was fine all right. But she said that the femur (thigh bone) length is measuring at 25 weeks, and the head is measuring at 28w plus a few days (28 weeks was when I got it done).

She added a whole lot of caveats. There is a lot of variation in dating in the later parts of pregnancy, and the later you go the more variation there is, sometimes amounting to 2 or 3 weeks of error in dating. But on the other hand, it could be indicative of a "mild form of dwarfism."

Then she put on her "let's look on the bright side" face and went on about how in some populations, mild dwarfism is common and you can hardly tell; and how it's probably because I have short legs and arms myself. (I do? Then why did all those boys in highschool call me "legs"? And why can't I find pants long enough?) And, anyway, it could always just be tech error or something and I shouldn't get myself worked up; but she wants me to go in for another ultrasound next week and see her afterwards to follow up.

So I have an ultrasound appointment next Wednesday, and another Ob appointment next Thursday. And then another appointment the week after that on the usual 2-week schedule (from today). Good thing I have so little work to do or this might be a problem.

Of course I'm freaking out. How could I not be? I have no idea what "mild dwarfism" might be, or what to expect, or how the hell it could pop out of nowhere at an ultrasound at 28 weeks when there was no evidence of anything at 20 or 22 weeks (the last ultrasounds).

Now that I've done some research I've even more confused, although slightly less overwhelmed.

For instance, I have no idea what "mild dwarfism" might be since it's genetic. You either have it or you don't. That's like saying, I don't know, partial cancer.

On the other hand, because it is genetic and they've identified which gene, they can do testing to make a definitive diagnosis. If they have to.

The one place I could find where they actually talked about ultrasound diagnosis of dwarfism, they said it was usually diagnosed at 20 weeks and indicated by a difference in dates of 4-5 weeks between femur length and head measurements. So a difference of 3 weeks dating at a 28 week ultrasound doesn't sound like the same thing at all. On the other hand, this is the only source I could find on the subject, so goodness only knows if it's reliable. And 3 weeks still sounds like a lot.

There isn't much information to be hand on the variability of ultrasound scans. I did find what the conditions were for ensuring accuracy in measurements, so you can bet I will be asking lots of questions next Wednesday.

I don't know what to think.

Apparently dwarfism is usually associated with some developmental delays, but that's just related to the skeletal differences; intelligence is normal.

I'm trying to figure out what this ultrasound means so I can either reassure myself between now and next Wednesday/Thursday or begin to get used to the idea. But it's hard. The most common form of dwarfism only affects 1/25,000 births, so there is not a lot of information available on its diagnosis, especially prenatally. What there is is very vague--"look for foreshortened limbs." Well great. How foreshortened is "dwarfism" vs. someone with short legs?