In 2003, the Centers for Disease Control and Prevention (CDC) reported that 26% of abortions in the United States were known to have been obtained at less than 6 weeks' gestation, 18% at 7 weeks, 15% at 8 weeks, 18% at 9 through 10 weeks, 9.7% at 11 through 12 weeks, 6.2% at 13 through 15 weeks, 4.1% at 16 through 20 weeks and 1.4% at more than 21 weeks. 90.9% of these were classified as having been done by "curettage" (suction-aspiration, dilation and curettage, dilation and evacuation), 7.7% by "medical" means (mifepristone), 0.4% by "intrauterine instillation" (saline or prostaglandin), and 1.0% by "other" (including hysterotomy and hysterectomy).[132] According to the CDC, due to data collection difficulties the data must be viewed as tentative and some fetal deaths reported beyond 20 weeks may be natural deaths erroneously classified as abortions if the removal of the dead fetus is accomplished by the same procedure as an induced abortion.[133]