ORANGE, CALIF., SEPT. 20 -- The birth of a 6-pound, 10-ounce boy to an apparently unrelated surrogate mother has intensified an unprecedented legal dispute here, with the birth mother pleading for a chance to remain in the child's life while the genetic parents seek full custody.

Attorneys for Anna L. Johnson, the first surrogate mother publicly to demand parental rights and custody of a baby developed from another woman's egg, said today that she was dropping charges of negligence and fraud against Mark and Crispina Calvert and hopes that all three can share in the child's upbringing.

Robert Walmsley, an attorney for the Calverts, said they were willing to discuss "any suggestions" with Johnson but would continue their legal fight for full parental rights and custody. The Calverts have paid Johnson half of the $10,000 agreed upon to carry their child.

An Orange County Superior Court judge is expected to rule soon on temporary custody of the child, born here Wednesday. Johnson's attorney, Richard C. Gilbert, said she "is extremely frightened that the baby will be taken from her."

Although DNA tests are not complete, Gilbert said he is willing to concede that the Calverts are the genetic parents. DNA, or deoxyribonucleic acid, contains the genetic code.

A court-appointed attorney for the child, who has been named Christopher Michael by the Calverts, indicated that he would recommend putting the apparently healthy baby, whom Johnson has been breast-feeding, into foster care if the two sides cannot agree on another arrangement before a custody trial expected within two months.

"How can it be in the baby's interest to take that baby away from the breast of the birth mother?" Gilbert asked this morning.

At a midday news conference, the Calverts said they would prefer temporary foster care to leaving the infant with Johnson and expressed a mixture of sympathy for and distrust of the woman who they said initially volunteered to help them have a baby.

The Calverts were unable to have children on their own. Crispina Calvert had a hysterectomy in 1988. They have not seen Johnson since June, two months before she sued for custody and labeled them unfit parents for allegedly neglecting her and the unborn child. The Calverts were allowed to visit the baby Wednesday night in the St. Joseph Hospital nursery without Johnson present, and today they talked effusively about their 30 minutes with him.

"He looks like us," said Crispina Calvert, 36, a nurse born in the Philippines. "He looks like an Oriental baby with my husband's nose."

Her husband, who is of British descent, said, nevertheless, "He's a Caucasian baby. There's no doubt looking at him that he's our child."

Both sides denied racial motives in the dispute, although Gilbert said Johnson, 29, who is of Native American and African descent, may have some rights to the child under federal law regulating adoption of babies born to members of Indian tribes.

Walmsley disagreed, saying, "He's not an Indian baby," and adding, "We would refute any claim that we are trying to bring bias or prejudice into this case."

Experts estimate that as many as 4,000 babies have been born to surrogate mothers in the United States, occasionally causing bitter legal disputes about parental rights. But most of those were conceived by artificial insemination of the surrogate's egg.

Walmsley, whose Santa Ana firm has dealt with many such cases, said only about 80 infants have been born from embryos created by combining eggs and sperm in a laboratory and implanting them in unrelated surrogates. This is the first such case to produce a publicized lawsuit, he said.

Johnson and Crispina Calvert met at the Orange County hospital where both worked. To save money, they signed a surrogate contract form. They received very little legal counseling before Johnson apparently was successfully impregnated with the Calverts' lab-produced embryo on the first try. Some scientists described it as a 1-in-10,000 occurrence.

Gilbert cited a recent opinion by the ethics committee of the American College of Obstetricians and Gynecologists favoring rights even for unrelated surrogate mothers and said Johnson was receiving advice from Mary Beth Whitehead, the surrogate mother who received visiting rights in the bitterly contested "Baby M" case in 1987.

Walmsley noted that Whitehead, unlike Johnson, was the genetic mother, and he cited a recent statement by the American Medical Association affirming a couple's ownership of frozen embryos made from their eggs and sperm.