Wearing a white hospital coat over his green surgical tunic and pants, Mayor Marion Barry came out of the Columbia Hospital delivery room yesterday with a box of cigars and announced, grinning with relief, "It's a boy."

Just two weeks short of full term, the baby weighed 6 pounds, 7 ounces, the mayor said, and was 19 inches long. It is the couple's first child.

Born at 5:44 p.m., the baby will be called Marion Christopher Barry.

Barry, who assisted his wife Effi in the natural childbirth, said, "As the baby was coming out and I was holding him up I kind of had tears in my See BIRTH, B7, Col. 1> eyes." Barry said the mother was doing fine.

He was still wearing his green surgical boots and hat as he offered the cigars to reporters and nearby hospital workers. Barry looked relieved and more relaxed than at any time during the long day which began at around 9:20 a.m. when his wife called him on his private office line to announce, calmly at first, that the baby was coming.

A few minutes later, Barry said, she called back -- this time wondering with some concern what was taking the mayor's chauffeur so long to pick her up for the ride to the hospital.

"Where is he?" Mrs. Barry demanded, according to the mayor.

The chauffeur finally arrived, and then swung past the District Building to pick up Barry, and they all made it to the hospital shortly after 10.

One of the first things Barry did was to change from his gray business suit into a sports shirt and slacks. He said he had learned from the childbirth classes the couple took at D.C. General and Columbia Hospitals that he should wear "something comfortable."

Barry said he and his wife were impressed with the facilities at Columbia Hospital where, a hospital spokesman said, 20 percent of all babies born in the District are delivered. Julie Nixon Eisenhower, was born there in 1948. Basketball star Kareem Abdul-Jabbar and his wife had their child at the hospital, as did singer Marvin Gaye and his wife.

"Childbirth classes get you ready for all this," the mayor said unconvincingly, during one of his brief visits to a jury-rigged press headquarters set up in a wood paneled conference room. "The main thing is just your physical presence and support," he said. "And they teach you other things -- they teach you how to breathe with her . . . pant . . . pant . . . puff."

Reporters whiled away the hours playing cards and speculating on whether the child would be a boy or a girl. Mrs. Barry underwent a test that revealed the sex of the baby during her pregnancy, but the results were known only to the mayor. "I didn't even tell Effi," Barry said. "It's the best kept secret in town."

Barry had said that if it was a boy, it should be named Marion Barry III. Effi disagreed, but added, "I do understand that this may be his first and only child, and I understand the act of pride that is part of sharing his name." She also admitted, however, that she had consulted a lawyer friend to see who had the right to name the baby.

If it's a girl, the mayor reportedly told her, "You can name her anything you like."

Her response was: "Thanks a lot, friend."

Barry spent most of his time with his wife, comforting her and aiding the delivery process, he said. Early in the day he and city press spokesman Alan Grip attempted to get some work done, but the efforts failed after only a few minutes of trying. "I can't concentrate," Barry said. "I am pretty wrapped up in all of this."

Barry did take time to accept a call from a White House aide, who wanted to know how Mrs. Barry was doing. The expectant father beamed as he reported that everything seemed to be going well and that doctors expected the baby to be born by early evening.