The Church even dictated how you were supposed to have sex. Anything other than the common “missionary position,” for example, was considered unnatural and therefore a sin, according to the Church. The woman on top position, or entering her from the rear (sex a tergo) were not favored because they interfered with the natural order of male-female roles. Anal and oral sex were sins because they could only be practiced for pleasure, not procreation, which for the purists was the only purpose of sex.

Punishments for those using “deviant” sexual positions could be very harsh: three years' penance for the woman on top and the same for both oral intercourse and sex a tergo, which was generally seen as the most sinful position ... with the possible exception of anal intercourse.

These were the official ideas of the Church, but some “progressive” theologians began to question these ideas. Albertus Magnus named five sexual positions and ranked them from most acceptable to least acceptable: 1) missionary, 2) side-by-side, 3) sitting, 4) standing and 5) a tergo. Magnus said the missionary was the only completely "natural" position; the others were "morally questionable but not mortally sinful. In certain situations, however, (such as extreme obesity), these other positions could be not only acceptable but even practical...