Original sentence: Certain forms of birth control are used to prevent implantation of the fertilized embryo to the womb.These acts of emergency contraception are not classified as abortion by recent medical difiintions, however some people do consider pregnancy to begin at the moment a sperm and ovum unite to form an embryo
Edited sentence: Certain forms of birth control are used to prevent implantation before the pregnancy occurs.These acts of emergency contraception are not classified as abortion by medicine