Mario Jones remembers how the conversation began: He was standing next to his girlfriend in her parents' apartment in Southeast Washington in February 1984. She was washing the dinner dishes when she suddenly whispered to him in a voice that only he could hear, "Mario, I want a baby."

Mario said he looked at her, trying to decide whether she was serious. He was 18, a high school graduate working for $4 an hour as a security guard at Iverson Mall and dreaming of running his own business some day. His girlfriend, Sheila Matthews, had just turned 15 and was in the ninth grade, an above-average student with ambitions of becoming a pediatrician. As far as Mario was concerned, this was no time to talk about having a baby.

Besides, Sheila's statement flew in the face of plans they had already made. First, they had agreed to wait until Sheila had graduated from high school, which was more than three years off. Then they would live together for a year before getting married. Once they were married and settled, they would attempt to have children.

But when it came to sex, they acted as if they had no plans. Birth control was a sporadic practice: Sometimes, Mario said, he used a condom. Sometimes Sheila kept track of her cycle so they could avoid the weeks when she was ovulating. Sometimes they used no birth control at all. In the heat of the moment, Mario said, "Sometimes you just want to take that dangerous chance."

Mario had often taken such risks with his girlfriends but had been lucky so far. He said that when he was younger -- he had his first sexual experience at 14 -- he pretended he couldn't produce a child "even though I knew I really could." Now he made no such pretense, so when Sheila whispered to him in her parents' kitchen that she wanted a baby, it made him uneasy. "I said, 'Sheila, you got to be joking. For one, I can't afford a baby right now. For two, you are too young to be having a baby right now.' "

None of that mattered to Sheila, according to Mario. A few weeks later, she told him: "I'ma having a baby . . . . You're gonna give me one."

Sheila remembers the conversations, but she remembers them differently. She said they took place later, in May and June 1984, and they were her way of preparing Mario for the possibility that she might become pregnant -- or might already be pregnant.

These conversations, whenever they took place, did not change the couple's sexual habits. They still had sex frequently, sometimes at a local motel, and they still used birth control haphazardly. One day in early June 1984, Sheila told Mario that she was pregnant. She was scared and confused.

Mario immediately insisted on an abortion. But Sheila, a practicing Baptist, said she couldn't go through with one, that she didn't have the right to "take away" the unborn baby's life. Mario finally agreed to deal with his new role as best he could, but the argument nearly ended their relationship. Since that time, they have gone through periods of rarely seeing each other.

On Jan. 14, 1985, Mario Pierre (Petey) Matthews was born. If his birth was not planned, that no longer mattered. Perhaps, in the end, all their plans -- Sheila's graduation and hopes of becoming a pediatrician, Mario's desire to own his own business -- amounted to nothing more than a kind of teen-age fantasy, easy to believe in but nearly impossible to achieve.

Now the questions were: How would they take care of their newborn baby? And would they do it together? Sheila: Growing Up

Sheila said the dreams started in the summer of 1983, when she was still 14. In her dreams appeared a tall silhouette, a man who not only became her lover but treated her "like a lady." She said to herself, "This man loves me, whoever he is."

After she met Otis Mario Jones in September 1983, she came to believe that he was the silhouette in her dreams. Mario is tall and lanky, with a dark brown complexion and dark eyes, closely cropped hair and, at times, a thin wisp of a mustache and goatee. He is blunt-spoken about himself and others, and he alternates between being furious with Sheila and being deeply in love with her.

In Sheila's social circle -- both at school and in the area around Barnaby Road SE where she lives -- Mario represented something else: Mario gave Sheila prestige.

He was, she said, "one of those guys from Maryland," someone who grew up outside the poor Washington Highlands community where Sheila lived. He was older, a graduate of Oxon Hill High School and, when she met him through a friend, a student in business at Prince George's Commmunity College. He had a car, a 1971 Plymouth Fury, and a job -- and, Sheila told her girlfriends, he treated her with respect.

That was enough to impress her girlfriends, but she really drew their envy when Mario took her out for dinner by candlelight at a Tysons Corner restaurant: None of their boyfriends could afford such an expensive meal.

Sheila had been trying to outdo her friends since she was 11, when she found that her best friend was drawing the attention of the boys. "She had very large breasts and I had none," Sheila recalled during a series of lengthy interviews that took place over several months. When Sheila became upset, her mother bought her a padded bra and bikini underwear. "I felt good about that," Sheila said.

Sheila and her best friend competed in nearly everything, and most of the time the other girl led the way -- by getting a boyfriend first, menstruating first, getting birth control pills first. In August 1983, Sheila decided to get birth control pills, too.

She said she went to a local doctor, who agreed to write the prescription needed to obtain the pills. She put the prescription in her bureau drawer but before she filled it, her mother found it. As Sheila protested, her mother tore the prescription into small strips. Angry, Sheila said, she told her mother that she wanted to take the pills because her best friend was taking them. "Monkey see, monkey do," her mother said as she threw the strips into the kitchen trash can.

After she met Mario, Sheila said, she tried again. One day in October 1983, the couple got into Mario's car and drove to the Union Medical Center in Northwest Washington, where Sheila's family is eligible for free medical care because her father belongs to the construction laborers' union. She saw a doctor, who called her mother -- without telling Sheila, as was the doctor's prerogative in dealing with a minor -- and found out that her mother objected. The doctor then refused to prescribe the pills.

Sheila said she tried to get the pills secretly because she knew her mother would disapprove. She said her mother once told her, "If you get pregnant, you better not come home."

For one thing, her mother knew the family could not afford to care for another child. The family's only income came from Sheila's father's job as a laborer, and that money had to cover the cost of feeding and housing Sheila, her two older brothers and her younger sister. The six of them live in a small, two-bedroom apartment in privately owned Jeffrey Gardens, a run-down, partly boarded-up complex just inside the D.C. line.

Sheila's mother has lived on the edge of poverty for most of her life. She grew up in the tobacco country of North Carolina, the youngest of 14 children in a sharecropping family. She met Sheila's father 26 years ago and they have lived together for most of that time.

Sheila's father did not want to be interviewed for this article. Her mother talked freely about the trials of the family's daily life -- how financial problems led her to take a part-time job as a domestic worker, how they worry about paying the rent each month -- but declined to discuss her past in detail.

Sheila said she decided at an early age that she did not want to live the way her parents had. She said she still felt that way when she met Mario Jones. Mario: Growing Up

Mario Jones said he never expected to fall in love with Sheila Matthews.

It started out as a lark, a foray into the Washington Highlands neighborhood, where girls had the reputation for being "fast." One night in September 1983, one of Mario's friends wanted to see his girlfriend in Washington Highlands, and he asked Mario to drive him there. He told Mario he would introduce him to a girl named Sheila.

"At first," Mario said, "I wasn't looking for a relationship. I was mainly looking for something fast. But Sheila seemed like a whole different person from what I was expecting."

She was anything but fast. They did not kiss for weeks, he said, and she was clearly inexperienced when it came to sex -- far less experienced than Mario, who had had lengthy sexual relationships with two girls before he met Sheila. Still, he said, he was strongly attracted to her. Although she was just 14, she had a quality that set her apart from his other girlfriends.

Sheila is diminutive, barely 5 feet tall, with a broad, expressive face and round cheeks. She appears shy at first, but that shyness gives way to a kind of combativeness, especially in her relationships with her mother and with Mario. She is religious, regularly attending services at the Atlantic Street Baptist Church near her home, singing in the lead position in the church choir.

Mario had been involved with other girls before meeting Sheila, and he had an active sex life. Some girls insisted he use a condom, while others did not seem to care; Mario said he rarely brought up the issue himself. Some girls insisted that their lovemaking only go so far; despite those good intentions, Mario was not always careful. One 14-year-old girl, who already had one child, would get mad at him for being careless. "She would cuss me out," Mario recalled. "She would call me a name. Get on me a little bit. She would say, 'I told you not to do that.' "

In Mario's circle of friends -- he was born in Southeast Washington and moved with his family to Oxon Hill when he was 10 -- fatherhood means responsibility. He said he felt pressure -- from himself and from Sheila -- to help care for Petey, mostly by providing money. When Sheila was pregnant, the pressure became so intense that he started to pull away from her, he said.

"I really tried to block her out," he said. "I tried to block her completely out of my mind. She wasn't listening to what I had to say and was thinking that everything was going to be cotton candy. I told her, 'There's gonna be financial problems. It's gonna restrict you from what you want to do.' She just looked at the whole thing like it wasn't gonna be a problem . . . . All she was thinking about was just" -- and his voice got louder -- "having the baby." Under Pressure ----------

On the night of Oct. 30, 1984, Veda Usilton was at home watching the television news when something caught her eye. The news story concerned a hearing on teen-age pregnancy held that day at Ballou High School -- an issue of some concern to Usilton, who counsels junior high school students at a city school. But it was not the subject that drew her attention. It was the appearance on the screen of 15-year-old Sheila Matthews, testifying about how she got pregnant five months earlier.

Usilton, who is not easily surprised after years of counseling teen-age girls, was shocked. She had known Sheila for several years and had been her counselor in seventh and ninth grades at Friendship Educational Center, a city elementary-junior high school on South Capitol Street in Washington Highlands. She thought of Sheila as a cut above most students -- bright, alert, able to hold her own. Many of her students have come to her with questions about sex, but Sheila never did.

Usilton has given up trying to stop ninth-grade girls from becoming sexually active. Young girls in Washington Highlands see sex as a natural part of their lives, she said. But many girls pretend to themselves that they can't get pregnant and that birth control is unnecessary because they're "not doing that much," she said.

To make her students confront reality, Usilton holds occasional "rap sessions," which have shown her that students feel tremendous peer pressure to have sex. She summed up their feelings this way: "It's not cool to be an A student. It's not cool to be a virgin. It's not cool to say you're a virgin. You shouldn't be on birth control."

Sheila Matthews, too, felt that pressure, according to her mother and Mario. "She noticed that all her friends were getting pregnant," Mario said, referring to two of Sheila's closest friends.

Shortly after Petey was born, Mario said, Sheila began teasing him, in front of her mother, about her desire to have a second child. Mario was taken aback. He remembers the conversation this way:

"Not by me you won't," he said.

"Yes I will, too," Sheila said.

"You only wanted this one because all your friends had one," Mario said.

"I did not," Sheila shot back.

Suddenly, her mother interrupted, looking directly at Sheila.

"He's telling the truth," her mother said. Making New Plans

On a cold, sunny Sunday in February 1985, about a month after Petey was born, Sheila bundled the baby against the 38-degree temperature and went to sing in the choir at the Atlantic Street Baptist Church as she had done on so many Sundays before he was born.

She donned the green and beige robe, cradled Petey in her arms and took her place before the congregation. She felt secure in the church -- the pastor, the Rev. Milton Wilcher, had told her after she got pregnant that she was still welcome -- but the rest of her life was in turmoil.

Her mother had made clear that Sheila's father's earnings as a laborer were not enough to feed the family and Petey, too. Sheila was missing time from Ballou High School, where she was in the 10th grade, because she had no money for a baby sitter and her mother had refused to take care of Petey every day. In April, she dropped out of school.

Mario's life, too, was in turmoil. He had recently lost his $150-a-week job as a warehouse clerk and had no money to pay for Petey's disposable diapers and milk. He was living with his grandparents after a bad fight with his stepfather. He was arguing with Sheila constantly about money for Petey and seeing her sporadically because he was dating another girl.

He finally broke up with that girl in April and reconciled with Sheila. Since then, their relationship has been closer, but they still have their rocky moments.

He was out of work for three months before he found a job in April as a pizza delivery man, making $60 a week after taxes. A month later, he got a better-paying job at a messenger service firm and now works as a security guard at a Crystal City office building, making $130 a week after taxes. He earns enough to give Sheila a little money for 1-year-old Petey, but he needs $197 for his monthly car payment and $100 a month for rent to his grandparents.

Now, after months of just trying to cope, he and Sheila are making plans again. They are talking about getting their own apartment and living together for a while before deciding about marriage. Meanwhile, Sheila has enrolled in night school, which begins in early February. She will turn 17 on Feb. 16, and Mario will be 21 on Feb. 17.

For now, they have put off any long-term plans. Mario said he still wants to run his own business and to earn enough money to be financially independent, but he hasn't decided what kind of business or how he would find seed money to get started. "See, I don't really care what the business is. I just want my own business because that's how I know I'm going to make it," he said.

He said he wants Sheila to finish school and get some sort of vocational training, "just in case she has to get a job." But Sheila said that if Mario's dreams come true, if he makes it as a businessman, she wants to stay at home and run the household.

Sheila knows one thing for certain: she wants to move out of Washington Highlands. The neighborhood, she feels, "is treacherous."

"You have to look both ways" when leaving her apartment building, she said. "I'm looking for drug addicts. I'm looking for the police. I'm looking for gunshots. I'm looking for people stampeding over my baby."

If things go their way, Mario said, they see a "good life" for Petey. "What I don't want," Sheila said, "is to be living from paycheck to paycheck."

NEXT: The extent of the risk