"In the papal encyclical Casti Connubii (“On Christian Marriage”) by Pope Pius XI, birth control is described as a “criminal abuse” by those who “frustrate the marriage act” by committing “a deed which is shameful and intrinsically vicious.” No excuse is valid including “difficulties… on the part of the mother or on the part of family circumstance.” Furthermore, “no reason, however grave, may be put forward” to justify the use of birth control. Those who feel overwhelmed by childrearing have no excuse and are guilty of sinful lust, “wish[ing] to gratify their desires without their consequent burden.”"