More than 150 couples who once might have thought they'd never celebrate Mother's Day gathered for a party Saturday with their children conceived through in-vitro fertilization.

The families brought about 175 children who were conceived at the Jones Institute for Reproductive Medicine at Eastern Virginia Medical School. More than 500 children have been born through the institute, the most successful in-vitro fertilization program in the country.The families are among the lucky few; about 20 percent of the couples who go through the program emerge with a baby. Under the in-vitro process, eggs and sperm are mixed in a petri dish and the fertilized eggs are placed in the uterus.

"I felt I couldn't miss this," said Rochelle Foster, 41, of Matawan, N.J., as she held her 1-year-old son, Jonathan, at a picnic on the medical school grounds. "It's nice to see all the successful people together because when you're actually down for a cycle . . . you don't know who's going to be the ones who are going to be successful."

Foster made five attempts to get pregnant in three in-vitro programs before she succeeded on her second try at the Jones Institute.

"I had been trying since 1976 to have a baby," she said. "I didn't think I was going to have a biological child."

Janet Adams of Chesapeake went through in-vitro fertilization three times before she got pregnant with triplets, 3-year-old Bradley, Travis and Ryan. "I got my money's worth," she said.

Robin and Danny Morris of Weston, Conn., showed up pushing two double strollers that carried their 21-month-old quadruplets - Sabrina, Tyler, Jesse and Paul.

Mrs. Morris, who was the first to deliver quadruplets in the Jones program, said she had always wanted a large family.

"I couldn't go through in vitro four times," she said. "I got it all at once. It was terrific."