The city government ventured onto an emotional minefield last week when a City Council committee held public hearings on a proposed bill that would open D.C. court and adoption agency records to adopted children when they reach the age of 18.

Only three states - Alabama, Alaska and Kansas - now have similar legislation. District adoption records, as records in all other states, now are sealed. The D.C. records can be opened only when a court decides that disclosing the information will "promote or protect" the welfare of the adopted child. In general, courts have allowed access to information such as medical histories of biological parents when adoptees present a serious need for it, but they have refused to disclose names of the biological parents.

The bill now being considered by the City Council's five-member Judiciary Committee was introduced by Council Member Hilda Mason, who said that her father was an adopted child "who searched for his mother for 76 years" but never found her.

Nearly 20 adoptive mothers, biological mothers and "adult adoptees," as several identified themselves, testified in support of the bill, sometimes in tears and in voices strained with emotion. The approximately 10 opponents were representatives of adoption agencies and a few adoptive parents, who predicted an increase in black market adoptions and abortions if biological parents who give up their babies could no longer be guaranteed anonymity.

There has been a growing movement in recent years among adult adoptees to search out their biological parents and to press for legislation that would allow free access to records by adoptees when they become adults.

Norah Boyle Reap, who lives in D.C., said that in her search for her biological mother "it is not a question of my rights that impels me but a desire to reconcile and reassure. I need to know that the 20-year-old Georgia girl who gave me up for adoption is not a 50-year-old woman plagued with doubt or guilt or uncertainty. It was the right decision for her, and it has been the right decision for me."

Reap termed "groundless" the fears "of many adoptive parents that the children . . . will prefer the natural parents. In my case, the search has brought my (adoptive) mother and myself closer."

The youngest supporter of the bill was Rachel Jillian Smith 8, the adopted daughter of Nancy S. Smith, who also spoke on behalf of the law change. "I am in favor for the law that all people who are adopted should have there (sic) fair right to find out who there biological mother is, and I also think that people who don't want to don't have to," said Rachel, wrote the statement that she read.

Several witnesses emphasized the need for quick and easy access to family medical histories aa a reason for supporting the bill.

Doctors "feel (that) optimum medical care of adoptees involves the full medical history of the birth family," said Dr. George Cohen, a pediatrician who said he represented the 100-member D.C. chapter of the American Academy of Pediatrics. "Many diseases . . . are inherited but manifest themselves only later," he said, and knowledge of such and illness in a person's biological family helps the doctor plan preventive treatment. Cohen also urged that adoption agencies "maintain contact with the birth family to update medical information."

Another witness, Doris M. Barse, said she is helping her adopted daughter, now an adult, search for her birth parents, in part because of the need for a medical history. A recent warning by doctors that a drug used widely by women in the 1950s and 1960s has caused gynecological problems and in some cases vaginal cancer in their daughters "galvanized me to support this bill," said Barse. "It could be a life or death situation."

Committee Chairman David A. Clarke pointed out that the present District law provides for disclosure of medical records to adoptees and said in an interview after the hearing that he "didn't hear any evidence today that the law was not working."

Hereditary illneses sometimes develop after adoption records are sealed or were never provided in the first place by biological parents, making contact with the parents the only way to obtain the information, said other winesses.

Patricia Miner, who was adopted in D.C. in 1948, said that she recently "met my biological female parent and discovered that she has diabetes, which she did not have at (the time of Miner's) birth . . . I learned that my male biological parent died of a heart diseased at an early age."

What Clarke described as "a desire to learn about their heritage and roots" was the theme of testimony by several adoptees. To fill this need, the councilman said, "we've got to fashion something." He said he is "leaning in the direction of making an intermediary connection" that would establish a means of helping adoptee and biological parents to make contact through an agency that would first establish that both parties want to meet.

Most of the social workers and adoption agency officials who testified echoed the views of Ruth Dub, executive director of the Barker Foundation, who said that "I have to protect the silent majority" of biological parents who have been guaranteed anonymity. She suggested as a compromise a "national register of biological parents and adult adoptees seeking meetings . . . We feel it is mandatory that a system be established so that counseling an preparation can be part of each meeting."

Representatives of Catholic Charities, the largest private adoption agency in the Washington area, and of Family and Child Services opposed the bill for similar reasons.

A bill in Maryland that would have allowed adoptees access to court records was killed earlier this year by a 5 to 3 vote of the state Senate Judicial Committee.