NEW YORK, OCT. 28 -- The head of GynoMed Pharmaceutical Inc., the tiny start-up company that will sell a new intrauterine contraceptive device called the Copper T 380A, said today it would take "a conservative and educational approach" to marketing the product.

The company will sell the Copper T only to "qualified" physicians and family-planning clinics after marketing begins in the first half of 1988, Chairman Roderick L. Mackenzie told reporters here. The target physicians will be the estimated 10,000 to 12,000 obstetrician-gynecologists who insert IUDs.

Mackenzie also said that outside medical and legal advisory boards have approved information packages intended to ensure that prospective users give informed consent.

The doctors and clinics will be asked to confirm "in writing that they have received and understood the information and that they will inform women," he said. The company's president, Herbert H. Spoon, said women will be given a printed informed-consent form patterned after one pioneered by Alza Corp., maker of the Progestasert IUD, the only IUD currently available in the United States.

Mackenzie spoke at a press conference held by the Population Council, the international nonprofit organization that developed the Copper T and calls it "safe, effective and convenient when used according to labeling instructions."

The Copper T is a T-shaped plastic device. It has copper sleeves on the arms and copper wire coiled around the vertical shaft. The council said the copper accounts for the device being "the most effective IUD available anywhere," particularly for women over 25 who have had at least one child.

The Copper T is the product of a decade of research, and has been tested and used by more than 3,500 U.S. women, the council said. The Food and Drug Administration approved it in 1984.

Council President George Zeidenstein said GynoMed was chosen as the U.S. licensee after a lengthy search for a financially responsible company that would take a "responsible marketing approach" and discount the price of the Copper T for family-planning clinics.

Mackenzie said it is too early to specify prices, partly because a manufacturer has yet to be chosen, but promised a discount to clinics of at least 50 percent. Copper Ts for foreign distribution are made by Finishing Enterprises of North Tonawanda, N.Y.

A 5 percent royalty will be paid to the council by GynoMed, which Mackenzie founded in 1984 in Somerville, N.J. A cadre of eight people is building sales and other teams.

GynoMed's Spoon said in an interview that the company will "very conservatively" claim a pregnancy rate of 1 per 100 in the first year of use, which ranks it with birth control pills. The rate reported in studies recently summarized in an international journal by Irving Sivin, a Population Council scientist, was 0.5, compared with 2.9 and 2.5, respectively, for the CU-7 and TATUM-T, the last copper-bearing IUDs on the U.S. market. G.D. Searle & Co. ended domestic sales of those IUDs in January 1986, blaming product-liability litigation.

The Copper T's "conservative" claimed cumulative rate after four years of use is 1.9 per 100, meaning that among 1,000 women who wear the Copper T for four years, 19 will conceive.

Mackenzie said GynoMed will "make it very clear to both physicians and patients just exactly who should not use the Copper T" -- women who have never been pregnant, have had pelvic inflammatory disease (PID), or have multiple sexual relationships.

"The Copper T is a valid alternative for women who are in a stable, mutually monogamous relationship, have been pregnant and are, preferably, over 25," he said. The council listed additional candidates, including women who are breast-feeding, and women who are at very low risk of contracting a sexually transmitted disease.