The document summarizes an article about a new law in Arizona that defines pregnancy as beginning two weeks before conception. The bill bans most abortions after 20 weeks of pregnancy, but calculates gestational age as starting from the first day of the last period, which is typically two weeks before fertilization. While doctors commonly use this method of calculating gestational age due to its convenience, there is disagreement in the medical community around whether pregnancy begins at fertilization or implantation. The new Arizona law's definition of gestational age effectively bans abortions two weeks earlier than the bill claims.