The executive director of a midwestern Planned Parenthood affiliate had just returned from a conference on birth control. A single parent, she was met at the airport by her 17-year-old son. As they turned onto the highway, he asked, with studied casualness, "Hey, Mom, did you bring home any samples?"

She gulped, she recalls. And said to herself something like, "Okay, Moment of Truth for sex educator." She took a deep breath and said, "Listen, son, I really don't think I'm the one to talk to . . . I'm not at all sure I want to know about your sex life . . . You know we have lots of counselors up at the clinic, but I do think you ought to talk to someone. After all, you don't want to hurt somebody . . . It should be a caring relationship . . ."

"Not to worry, Mom," the 17-year-old assured her. "She's 20 and she seduced me. And it was wonderful."

"All I can say," his mother says now, a few years later, "is that I was certainly glad it was dark. And he was driving . . ."

Some 1,200 delegates are in Washington this week for the annual conference of Planned Parenthood Federation of America, the burgeoning health-care provider and educational clearinghouse begun by Margaret Sanger, the founder of the birth-control movement in this country.

Planned parenthood was founded in controversy; Margaret Sanger had her times behind bars -- nine of them, her philosophical progeny will tell you proudly. In the last three- quarters of a century, Planned Parenthood has become a meticulously professional organization, with a medical affiliate known worldwide for its research in human reproduction and for the quality of its clinical care.

But now, again, it is steeped in controversy, this time from anti-abortionists, religious fundamentalists and others who oppose its philosophies and activities, or who merely flinch at the candor of its educational materials. Its clinics are firebombed, its meetings are picketed, its advocates are publicly excoriated.

"If we didn't have pickets," grins Daisy Voigt, the federation's media coordinator, "we'd think we weren't doing our job."

"Every time I write a column about the Right to Life movement, they want to kill me."

-- Art Buchwald in a luncheon speech to the Planned Parenthood delegates at the Shoreham.

Faye Wattleton is president of the Planned Parenthood Federation of America Inc. She is tall, lean, attractive and articulate, and barely has time to breathe at this conference with hundreds of specialists, all the delegates and scores of programs pulling her this way and that. She is unflappably efficient. The line forms to the right for everybody who "just needs me for five minutes or so . . ."

PP, she will tell you, is only an "advocacy" organization to the extent that it needs to protect itself as a health-care delivery service, its principal mission. More than 100 clinics offer counseling on teen sex and abortion and such services as prenatal care, pregnancy tests, infertility help, VD diagnosis, prenatal screening, menopause and cancer diagnoses.

But Wattleton concedes that today the organization "more closely approximates what it was in its beginnings . . .

"Margaret Sanger, after all, made the ultimate challenge to the political system and there were people passing laws all around her, trying to restrict the advancements she was making, and the fact that there were women lined up to enter her clinics didn't matter to them. They had their interpretation of what was moral and that was what it was going to be.

"And today we have the same phenomenon."

She cautions tolerance to "some of our people who are upset with the opposition, who feel we should somehow get Jerry Falwell off television. I tell them they have the right to be there, too. If they persuade someone to their point of view, that's fine. It's just when they tell me I MUST believe as they do, we differ . . . The opposition," she notes, "has a very broad agenda of repression and they desire to dictate by law, if necessary, a moral standard for the country."

From a projected Planned Parenthood TV-spot entitled "male involvement":

Man: Do you know a million teen-aged girls get pregnant every year?

Boy: That means a million teen-aged guys are going to be fathers.

Leonore Guttmacher remembers when women, even women who'd had babies already, would faint on a doctor's table while being fitted for a diaphragm.

A lively and energetic septuagenarian, Guttmacher volunteered to work in the Baltimore clinic about 1933. Her husband, an obstetrician, was Dr. Alan Guttmacher, who became the first physician president of the Planned Parenthood Federation of America, from 1962 to his death in 1974.

"He believed in the democratization of medicine," and made family-planning his life's work, his widow said. She too continues to believe that "the rich could get anything they wanted, from birth-control information to abortions and so forth, and the poor were very handicapped because they never knew where to seek knowledge and had no money to do it with."

Leonore Guttmacher, president of the New York State Abortion Rights League, says she's again involved with Planned Parenthood because "I feel we've gone backwards 100 years. Look at the whole political situation."

Retired Episcopal Bishop George Barrett moderated a workshop on ethics and theology.

He began with this story:

"Two elderly bishops were bemoaning the state of the world. One said, 'I just don't understand this new morality. I never slept with my wife before I was married. Did you?'

"The second bishop answered, 'I can't say. What was her maiden name?' "

Rabbi Balfour Brickner, former Washingtonian, now at the Stephen Wise Free Synagogue in New York and a member of the ethics panel, said this:

"Everybody knows God is a God who makes war and God is a God who makes peace. Does anybody ever think about God as a God who makes love? And if God makes love, does God wear a contraceptive when God makes love?"

And from a medical ethics professor at the University of Virginia and author of "Situation Ethics," 77-year-old Joseph Fletcher: " . . . I want to say carefully and without elaboration: Sex is morally acceptable in any form. Hetero, homo, auto, bi or poly. And looked at from the ethical perspective, or from the point of view of the moral philosopher, I want to add that what makes any sexual act right or wrong is its consequences, because in and of itself sex is neither good nor bad, neither praiseworthy nor blameworthy, and its ethical significance depends on the values it serves and seeks to realize.

"The bottom line," said Rabbi Brickner, "as related to appropriate standards of sexual conduct is the government and government moralists have to be prevented from imposing their standards on my sexual conduct. That must come from me and my convictions. . . ."

Less than 25 years ago, Ann McFarran had to show her wedding invitation to the Planned Parenthood chapter in Ann Arbor, Mich., before she could be accepted for a premarital checkup and contraception information.

As a student nurse, she was assigned to evaluate and report on Planned Parenthood.

Now she is executive director of a major Planned Parenthood network in northeastern Indiana with programs so innovative they have captured wide attention. Children's author Judy Blume, for example, cited a McFarran program of broadening parent-teen communication as one the foundation Blume is starting might consider financing.

It is a simple device for communicating. A group of youngsters and a group of parents write down what they would like to know or hear from the other. All parents and youngsters come to a discussion, and are divided into small groups. No parent may be in the same group as his or her child.

The theologians inserted a perhaps uncharacteristic levity into the discussion of ethics. Humorist Art Buchwald was similarly out of character -- but no less effective -- when he ended his luncheon speech on this note:

" . . . you're here in a pretty rough time. When it comes to civil rights, human rights and individual freedoms, the Reagan administration is turning back the clock. In your particular case, the people who are raising millions of dollars to fight abortion are the same people who are cutting out all funds to take care of the same babies once they are born.

"The irony is that the people who are concerned about protecting life are also fighting gun control, talking about nuclear war as if it were a World Series baseball game. They are using the abortion issue to raise money for political campaigns and defeat the very people who care about the poor, the minorities, the environment and the Earth. I wish you luck in your endeavors. You're going to need a lot of it with the people who are now in charge. I admire all of you for taking your time and spending your money on this issue. It's a battle that has to be won if you're going to keep the religious zealots from taking over this country and making it into a police state."

Buchwald got a standing ovation.