What are some reasons why some Christians may disagree with contraception? Add sources of authority.

Catholics believe that sex is used to make new life ('be fruitful and increase in number'), and contraception goes against God's purpose of marriage. The morning-after pill is considered abortion because it prevents the fertilized egg from implanting, so it's a sin. The Bible says 'Every sexual act should have the possibility of creating life'. The sanctity of life shows us that all life is sacred and holy, so we should accept and welcome it. The Bible says 'Be fruitful and increase in number'.