Abortion FAQ, continued: Why women have late term abortion

I keep a FAQ on abortion for my bioethics classes. I post the entries here, too, on the theory that if my students have these questions, other people might as well. Here is a post, from a student on the abortion discussion forum who is wondering about women who have late term abortions.

Most women find out they're pregnant at 4-5 weeks, why wait, if they know they're unhappy why not schedule an abortion as soon as possible?

The first thing to note here is that for the most part, women do have the abortion as soon as possible. As I explained in the abortion video, 88% of abortions are in the first trimester, and only 1.3% are in the third trimester.
The next thing to note is that a substantial number of women who have late term abortions are doing so for medical reasons. These are typically women who wanted to be pregnant, but have found out that something has gone wrong. Perhaps the pregnancy is endangering their life, or the child will not be able to survive after birth.
This still leaves a population of women who have abortion after the first trimester for something other than medical reasons. Here is an interesting study published in Perspectives on Sexual and Reproductive Health on women who have abortions after 20 weeks gestation for non-medical reasons. In your question, you state that most women know they are pregnant in the fourth or fifth week. This is not true, however, of the women having abortions after 20 weeks in this study. They report on average, finding out that they are pregnant in the 12th week of pregnanacy.
Interestingly, the authors don't wind up using the late discovery of pregnancy as one of their factors explaining later abortion. They identify five profiles for women who delay abortion after 20 weeks. Together they account for 80% of the women in their sample.

1. Women suffer from depression or drug addiction
2. Women who were in conflict with their partner or perhaps experiencing physical abuse
3. Women who were raising children alone
4. Women who had trouble deciding and then trouble accessing a provider
5. women who were young and had never had children before.

These categories overlap, so some women who delay abortion might be depressed and in a physically abusive relationship. I think some of these factors make the delay more understandable.