Just in case any of you out there ever get as obsessed with crown-rump length as I have, I have some good data for you.
Basically, my advice is to hell with the google searches. Everything I found on basic google searches or even google scholar freaked the living daylights out of me to the point where I was a pathetic crying lump on the bathroom floor last night because my breasts don't hurt anymore.
I am lucky b/c I work at a very large university with a medical school and a fantastic library. Unfortunately this isn't available to everyone. That is really too bad because Dr. Google was making me totally freak out, suggesting that my fetus was almost a week behind on growth, and suggesting that there is no variation in very early fetal crown-rump length. (While I logically knew that this could not possibly be true, emotionally I couldn't ignore it.)
I found a recently (2010) published paper in the journal "Ultrasound Obstetrics and Gynecology" (issue 35, pages 650-655) that is titled, "New crown-rump length curve based on over 3,500 pregnancies." This was published by a bunch of doctors from various institutions in the UK. Lead author is A. Pexsters.
I like him or her because this is what they told me.
At gestational age of 49 days (which is the number of days since CD1 of the last menstrual period), the average embryo was 8.0mm, and 90% of the 3,500 pregnancies ranged between 4.8mm to 11.5mm.
(figure from the paper explaining what crown-rump length is)
All of these 3,500 pregnancies resulted in healthy babies.
This puts my little fetus at the lower end, but only about 2 days behind the mean and well within a comfortable range of variation for it's age.
I love libraries.
I'll email a pdf of this article to anyone who wants it -- just let me know!
(btw, I'm still freaking out and preparing myself to be diagnosed with a miscarriage on Saturday, don't get me wrong here. But this little piece of data at least got me off the floor.)
