Ninety percent of all abortions are provided during the first trimester, which is up to fourteen weeks gestation. A small percent (9.9 %) are performed during the second trimester. A very small percent (0.1% of all abortions) are performed in the third trimester, usually because of severe health problems in the fetus or the woman. As for legality, each state has their own regulations on the timing of abortion procedures. For more information, check out the National Abortion Federation website.