Gender Selection Is Getting Easier

From the New York Times:

Test Can Tell Fetal Sex at 7 Weeks, Study Says

A simple blood test that can determine a baby’s sex as early as seven weeks into pregnancy is highly accurate if used correctly, a finding that experts say is likely to lead to more widespread use by parents concerned about gender-linked diseases, those who are merely curious and people considering the more ethically controversial step of selecting the sex of their children.

I've never fully understood why sex selection is ethically complicated for otherwise adamant abortion rights advocates. It's the only reason for an abortion where they cite discomfort, but they never fully explain why.  If the pregnant woman is a married, 25-year-old law student who wants to delay motherhood until graduation, it's her choice. I've never heard any abortion advocate suggest it isn't, even though the reason for the abortion seems pretty frivolous in such a case. However, if she introduces the baby's sex into the decision, all of a sudden the word "ethics" is included.