Fact: in the District, 58 percent of all children born last year were illegitimate.

Fact: of all the illegitimate children born in the District nearly 70 percent were black; 65 percent of all black children born in the city were illegitimate.

Fact: of all illegitimate children born in the District, 20.9 percent were born to teen-age mothers and more than 95 percent were born to black teen-age mothers. And of all low-birth-weight babies born in the city--children who run a high risk of encountering health problems that could damage their mental or physical development-- 90 percent were born to black teen-agers.

There is one last statistic. It concerns the lives of illegitimate children, and it tells what the high rate of illegitimate births, steadily climbing higher in the last 15 years, could mean in the future. The statistic is this: District officials estimate that 75 percent of the teen-agers in Cedar Knoll and Oak Hill, the city's detention facilities for teen-agers, were born illegitimate.

"Being born out of wedlock is a very unfair starting point," says Marian Wright Edelman, president of the Children's Defense Fund. The obstacles to a black child's success in life are outlined in a study published by Edelman's group earlier this year, "Portrait of Inequality." It reports that a black child is twice as likely to die in the first year of life as a white child. The black child is also twice as likely to live with neither parent and to drop out of school, and three times as likely to have his mother die in childbirth.

These numbers are for all black children, legitimate or illegitimate. Social workers and statisticians do not know the odds for illegitimate children, but they agree that the black illegitimate child really has almost no chance at all.

"If you are mugged by some black youngster, no one would stop and think what a tough life these children have had," says Edelman. "On the other hand, you've got to see beneath the macho routine . . . to understand that they are both victims and victimizers."

If illegitimate birth, particularly among blacks, is a well-known, statistically confirmed key to lifelong membership in the underclass, why then are black women having more and more children outside marriage? A 1970 Census Bureau report on illegitimate births explains the rapid increase since the 1940s as a result of the growing number of unmarried women of child-bearing age.

She's at home now with her mother and the baby. She recently got out to the stores and to see friends for the first time since her baby was born. She is 21, unmarried, and very happy. But she says she doesn't want anyone to be cruel and call her child a "bastard" so she asks not to be named.

The baby was the result of an on-and-off affair with her high-school boyfriend, a man she has known for six years. She had heard from him only twice since the child was born, she said in a recent telephone interview. "He thinks if he comes around here he'll get into a family thing and I'll start talking about getting married. I know he don't have a regular job and can't be paying to take care of no baby. I don't want to marry him. What I want to get married for?"

She has applied for welfare.

Did she want the baby? She hesitates. She didn't plan to have the child, but she was not using birth control. She calls birth control pills "pink poison," and says "he doesn't always have anything (prophylactics) with him." So they took a chance a few times. She was in her first year of night classes at business school, learning typing and basic accounting, when she became pregnant. She quit her job as a clerk at Woodward and Lothrop because of the baby. "You know, I'm not sorry it happened," she says. "I'd had an abortion, and I couldn't do it no more 'cause I really love children. It's going to be hard. We don't have a whole lot of money, but he's mine, and me and my mother, we'll take care of him."

According to social workers, one reason for the continued growth in illegitimate births is black women's--particularly uneducated black women's--opposition to abortion on moral grounds. And mothers often persuade their daughters to give birth, rather than have an abortion, even if it means bringing a child into an unstable family without a father and with no income except welfare. Putting the baby up for adoption is viewed negatively, too, according to social workers. The result: illegitimate children typically live with a grandmother.

"I think 50 percent of the children I christen are illegitimate," says the Rev. Knighton Stanley of the People's Congregational Church on 13th Street NW. "It's no fault of the children, of course. The children aren't so much illegitimate as the parents are illegitimate. I would not deny any illegitimate child the right to be christened, but I wish the parents would not force me to christen the child at the 11 o'clock service before my son and daughter.

"This wave of illegitimate children is symptomatic of the breakdown of moral values in American society. For the black family an illegitimate child is really a difficult situation because for so long, all we have had was our children."

Why don't more women use birth control?

"So many young people will tell you they didn't plan to become pregnant," says Kathy Cook of Baltimore's Single Parent Services. "If they had the ability to choose they would say no to getting pregnant, but you must remember that adolescence is a time when very little is planned and there is a lot of fantasy. In some cases they don't realize the cost of having a child. One 14-year-old told me she thought that $120 a month in welfare for her child was a lot of money. She didn't know."

Counselors say that not only are the odds against an illegitimate child's succeeding, but that when it is born, the child pulls down the parents' chances for success. Trying to support a child often forces teen-agers and young adults out of school and training for good jobs, and pushes them into menial, low-paying jobs.

There are two ways to view the dismal statistics surrounding illegitimate births among blacks. They can be seen as a call for society to help illegitimate children overcome the incredible odds against them, or as a warning to young black men and women to avoid illegitimate births if they care in any way about the quality of the life their children will live.

With the odds as they are, the smart money would have to be on not having a child.