To be honest,
As a traditional Catholic, I am confused in regarding the Catholic Church's stance on natural family planning.
I am even unsure about the orthodoxy of Paul VI's encyclical on birth control, Humanae Vitae?
After perusing an article on the BBC, it said that Pope Paul VI allowed natural forms of birth control (where one may engage in intercourse during the woman's infertile periods), however artificial birth control was strictly prohibited.
I wish someone can explain the traditional Catholic teachings on these issues.
RonCal,
There was no confusion on this issue, until the liberals twisted Pope Pius XII's teaching, and using the new renamed term, Natural Family Planning, allowed the floodgates to open with all sorts of novelties.
The second problem came about when certain writers, not content with correcting modernist abuse of the teaching on the lawful use of the rhythm, actually attacked the orthodox teaching of Pope Pius XII.
The truth can be found if you read
Casti Connubii Pius XI, and in the Address to the midwives by Pius XII, October 29, 1951, AAS 43 (1951). Do not let anyone confuse on this point, Pope Pius XII's teaching on this is authoritative, therefore it is safe, and it does bind Catholics under pain of serious sin to believe it.