Technically speaking, is it a `fetus' or is it an `unborn child'?

The Washington Post, in its Sunday story on the Peterson verdict, used the term "unborn child." The New York Times used both "unborn child" and "fetus." The Associated Press referred at one point to "the son she [Laci Peterson] was carrying" and in another to the "fetus." The Tribune was consistent in using "fetus."
Randy Weissman, deputy managing editor/operations, noted that that was consistent with the guideline in the Tribune's current stylebook.
However, a new edition of the stylebook, scheduled for publication shortly, will permit the use of "unborn child" when the fetus is in the third trimester of gestation.