Sunday Fetus Blogging

tiny unnamed fetus enters the second trimester today. (13 weeks post conception, 15 weeks post last menstrual period) According to the pregnancy calendar at parentspace it is 12.5 cm long and weighs 80 grms.

Last time I was reading on the issue, I came to the conclusion that this might actually be the time when the fetus becomes sentient. All of my citations on the subject are at the office, so I can't give you the details, but I remember I was impressed by two facts 1. Most of the second trimester is just rapid growth. You don't see a lot of new systems coming on line. 2. The pain circut that we share with animals (the delta fibers) is active at this point. The more advanced pain circut, the c-fibers which we only share with the other great apes, won' t be on line until week 28 or so. Well, if any of the pharyngula crowd heads this way, they might be able to correct me on the biology here. I do want to stand by a bit of conceptual analysis, though. I have a strong intuition that my dog can feel pain. If the fetus at this stage has roughly the same functioning hardware with a similar evolutionary history, I think it will feel pain too. Given the way reflective equilibrium works, one could deny sentience to both the 13 week fetus and dogs, but that is unsatisfactory.

I also, by the way, think that the fetus at this stage has the same moral status as my dog, which makes me out of touch with both pro-life and pro-choice hardliners, even though I consider myself pro-choice.

I had earlier wanted to post some composite pictures by Tsarias of the developing fetus, but a google image search didn't yield any. Now a link on pharyngula lets me know that Tsarias' company has an elaborate flash-based web page for all of their anatomical art. This is a deep link to the section on fetal development. If that doesn't work, this is the front page.

Tsarias's page has interactive graphics for the period from conception through implanation, for the 3-8 week period (technically known as the "boiled shrip stage"), and the third trimester (technically known as the "space baby from 2001 stage"). Nothing for what tiny unnamed fetus is doing now. The pictures from the boiled shrimp stage are cool, because they look more like menacing alien babies than pro-life propaganda posters. I only wish Tsarias' pictures came with more signage: explanations of the different sources used for the different images, what it means that certain systems were colored red, etc.