Babies could be conceived outside the womb of many American medical centers "within a year" and probably "within three months" if federal rules preventing the procedure were lifted and training of doctors began immediately, the doctor who created the world's first such "test-tube child" said yesterday.

Britton Patrick Steptoe thus took issue with the many Americans doctors, scientists and politicians who have said years of research-and careful consideration of the ethics of "creating life" - are necessary before any infertile Amercian woman can bear such a child.

The overriding ethical issue is the ardent desire of infertile couples for children, Steptoe said, and "a number" of American medical centers have physicians and reproductive scientists who could "with three months training" reproduce his methods. Tr for ad 1

To help in such training, he said, he might commute between England and Washington if an affiliation can be worked out with a Washington hospital.

In particular, he said, he and Dr. John Mariowe, director of medical education at Columbia Hospital for Women, have been discussing a possible joint venture.

Steptoe, the obstetric-gynecologic surgeon who delivered test-tube child Louise Brown in Oldham, England, in July spoke in an interview at Columbia Hospital as part of his first visit to this country since that event.

The British surgeon called the Department of Health, Education and Welfare regulation that has blocked all test-tube baby research in the United States since 1975 a serious "mistake" that is delaying help for thousands of women who want babies.

He said another child conceived in his laboratory is due "early next year," and other groups are working with prospective mothers in England and Australia, as well as in Calcutta, where an expert medical group delivered the world's second such child last week.

This kind of rapid development makes it possible that joining male sperm and female ova, or egg cells, in the laboratory soon could be classified as normal therapy for infertility, free of the restrictions placed on "research" by the government and hospital review boards.

Steptoe also disclosed several new facts about the methods he and his scientists-partner, Dr. Robert Edwards, used to conceive the Brown baby.

Until the Brown pregnancy, Steptoe and Edwards - and other doctors - had tried again and again, always unsuccessfully, to join sperm and ova, implant the resulting embryo into a would-be mother and bring the growing fetus to delivery.

Steptoe said he and Edwards had learned:

How to monitor the would-be mother's menstrual cycle to learn the precise time when the ovum could be taken from her ovaries.

How to make a hospitable "culture medium" or laboratory broth in which to join the female's ovum with her husband's sperm.

"The optimum time" (2 1/2 days in baby Brown's case) for implanting the growing embryo back into the mother.

Implantation must occur through the vagina and cervix rather than through a surgical opening into the womb, because it causes "the least distrubance" to embryo and mother during the crucial two weeks before the embryo grows large enough to attach itself to her womb.

HEW Secretary Joseph A. Califano Jr. this year named as Ethics Advisory Board to recommend, perhaps early next year, whether HEW should lift its 1975 moratorium on federally funded test-tube baby research.

The moratorium prevents even joining human sperm and ova in the laboratory because some persons argue that the resulting embryo is then "a human being" that many not be experimented with or destroyed.

Steptoe said that until implantation the embryo is merely "potential life," not a fetus. He argued that the benefits of studying such embryos - even if some must be discarded - are overwhelming. He said this study "of the first few days of our lives" may teach doctors how birth defects begin, and how to prevent them.