If you've ever viewed any postings or comments by Amanda Marcotte from Pandagon, you'll likely recall someone who attempted to defend the legality of abortion with a strong amount of passion and whose posts were often filled with profanity. You might recall her accusing prolifers of wanting to punish women for having sex. She also comes off (at least to me) as being very confident in her knowledge regarding the abortion debate.
But in recent comments on her blog she shows she doesn't have a firm grasp of fetal development.
Amanda doesn't seem to know that an unborn child's brain starts developing long before the end of the first trimester.
Amanda uses the term "brainless fetus," says, "But there's not even an argument in early term pregnancy; it doesn't have a brain and it's not a person, period" and "My point was just that there is no argument whatsoever for the personhood of a fetus before it has developed a brain."
But by the time the unborn child is a fetus (the eight week) she already has a brain and has had one for quite some time.
According to this medical encyclopedia, the brain of an unborn child starts developing at week 3 and during weeks 4 and 5 "the brain develops into five areas and some cranial nerves are visible."
More information on when the brain begins developing with citations to embryology textbooks can be found here.
You can also view some Magnetic resonance (MR) images of the brains of unborn children at various stages of development (as early as 12 weeks) here.