Prior to the 20th century, three major branches of Christianity—Catholicism, Orthodoxy and Protestantism—including leading Protestant reformers Martin Luther and John Calvin generally held a critical perspective of birth control (also known as contraception). Among Christian denominations today, however, there is a large variety of views regarding birth control that range from the acceptance of birth control to only allowing natural family planning to teaching Quiverfull doctrine, which disallows contraception and holds that Christians should have large families.