In the 1960s, the U.S. Food and Drug Administration approved a contraceptive that allowed women to plan desired pregnancies and prevent unwanted pregnancies. Oral hormonal contraception ('the pill') uses synthetic hormones similar in structure to progesterone and/or estradiol. What is the pill's mechanism of action?Use Table 47.2 to compare and contrast the mechanisms of action of emergency contraception and mifepristone to that of the pill. Which methods act as contraception and which act to terminate a pregnancy? Explain.