July 25, 2008 40th anniversary of "Humanae Vitae" Play video

(Greg Wayland, NECN) - It was a defining moment for the Catholic Church. Forty years ago Friday (7/25), Pope Paul VI issued an encyclical letter on sexuality and birth control.

1968. A war, urban riots, campus revolts and a sexual revolution. Most Christian religions had ceased to condemn artificial contraception. Many Catholics hoped their church would follow suit.

And Time magazine had extolled the birth control pill as "a miraculous tablet that....has changed and liberated the sex and family life of a large and still growing segment of the U.S. population." Dr. John Rock, a catholic, was one of its inventors.

Then in July '68 came a kind of bombshell from the Vatican -- Pope Paul the sixth's long-anticipated encyclical letter on the regulation of birth-- "Humanae Vitae" it re-affirmed the church's ban on artificial contraception.

Fitchburg, Mass family practice doctor Mark Rollo was eighteen and preparing for college.

"And I can remember, you know, people laughing at the Church. And I kind of sort of went along with that mentality of, you know, why can't the Church get with it."

Catholic editor and author Phil Lawler believes the pope agonized over his decision.

I get the impression that if he had seen a way to allow contraception within the framework of traditional Christian morality, he would have taken it.

Married love, wrote Pope Paul, "is above all fully human, a compound of sense and spirit." But, he

added , " to use this divine gift while depriving it, even if only partially, of its meaning and purpose, is equally repugnant to the nature of man and of woman, and is consequently in opposition to the plan of god and his holy will."

STEVE POPE "I would say the encyclical was one of the worst things that happened to the Catholic Church in the twentieth century"

But Dr. Rollo, a catholic, ultimately embraced the pope's teaching, added church-approved natural family planning to his practice, and claims it's vastly more reliable than the calendar rhythm method that proved so ineffective for generations of catholic couples.

Modern methods don't rely on a calendar at all. It teaches a woman to notice changes in her own body, which tell her when she's fertile and when she's not fertile.

Catholic couple Mark and Maureen Trettel claim its given them a healthy, happy marriage. "And it's not just on him, you know, or just on me. It's not my job to make sure. No question it's a duel responsibility. We look at this as a partnership for sure."

But to this day, influential catholic groups condemn the ban and polls repeatedly show Catholics ignoring it.

But Boston priest Fr.. Robert Imbelli says, over the next four decades, few American Catholics would learn about the encyclical, or have it explained to them.

I think there has been something of a loss of nerve on the part of priests, as thought things had been decided forty years ago and there's nothing further to say.

Some priests publicly revolted against the encyclical, Boston's cardinal Richard Cushing sent mixed signals , saying, " the issue is settled ....for now,"

.While resistance to the Church's teaching has taken many forms and come from many quarters, ironically, some of the strongest resistance has occurred on the campuses of Catholic colleges.

STEVE POPE The difficulty for many moral theologians such as myself is whether each and every act of sexual intercourse has to be open to procreation.

Boston college theologian Stephen pope believes the ban ignores reality.

Right now, the population of the planet's about six point five billion people. By twenty-fifty, at the current rate, it's going to go up to nine billion. What will that do to the environment? What will that do to our ability to sustain human life?

Others believe pope paul the sixth was prophetic.

You have to step back and say, well, wait a minute, was he right? And he also predicted more violence against women, more domestic abuse. Rollo: Governments are actually kind of reorienting their policies trying to encourage people to have babies.

MEANWHILE, THE MILFORD, MASS HOME OF MARK AND MAUREEN TRETTEL IS A PLAYGROUND FOR THEIR SEVEN CHILDREN.

People are going to say, you have seven children. I don't want seven children. Therefore, I'm not going to do this. What do you say to them? -- Well, his sister across the street has two children, they've been using NFP as long as they've been married...

Mark: Our oldest every once in a while will say, okay when are we going to have the next -- we're ready for another boy.

The trettels know as little as four percent of catholic couples worldwide are following their example.

Fr. Imbelli: But my hope is that now at the fortieth anniversary, rather than looking back, we can look ahead to see what is the promise of the encyclical.

And that might have been the dying hope of a lonely pontiff.