That, too, but it does not invalidate the defiance of God implicit in contraceptive behavior.
Use of artifical contraception is a sin against both sexual morality and social justice. However, if one changes one's contraceptive technique from artifical birth control to natural abstinence (periodic or not) to eliminate the sin against sexual morality, yet fails to change the contraceptive motive of wishing to avoid children you are obliged to have as a matter of social justice, a mortal sin remains, and in fact, it may be a sin so great that it invalidates one's previously attempted marriage, since a prior intent to not have children is grounds for an annulment, regardless of the use or not of artificial birth control to achieve that intention.