Confusion of trimester and viability. Consequences for abortion laws in the United States and abroad.

The present U.S. abortion law, Roe v Wade, is based on the trimester/viability concept. However, both concepts seem to be biologically ill founded and are likely to contribute to confusion regarding abortion laws. A survey of the abortion laws in individual states revealed a lack of uniformity. The time limit for abortion upon request varies from 13 to 28 weeks; nine states have no specific abortion law. This confusion also exists in other countries. Standards are lacking regarding requests for the dates of the last menstrual period, fertilization and implantation. Some states do not allow termination of pregnancy for maternal indications after 24 weeks, and the definition of maternal endangerment has rarely been addressed and remains vague. Only a few states have provisions for fetal malformation. Such terms as trimester and viability are not biologically founded and are likely to contribute to the confusion. The terminology should be clarified so abortion, contraception, birth control and other such terms are uniform.