LONDON — Women with family histories of serious genetic disorders now can have their embryos screened in the test tube before they are implanted into the womb, a doctor said Thursday who pioneered the technique.

Dr. Alan Handyside said the technique has been used only to determine gender but researchers at the Royal Postgraduate Medical School at Hammersmith Hospital hope the process can be refined to detect other genetic information.

Handyside said the technique has produced its first children.

He said he and his colleagues are screening women with a family history of so-called X-linked defects that strike only boys. In these cases, only female embryos are implanted into the mother.

The new procedure builds on techniques developed for in-vitro fertilization and prenatal testing, Handyside said from the west London hospital.

Like in-vitro fertilization, eggs removed from the mother are fertilized in a test tube where the embryos are allowed to grow for three days, Handyside said.

“You cannot implant an embryo beyond the third day so we begin work early in the third day when the embryo has multiplied to eight cells,” Handyside said.

He said there is a 12-hour window for completing the screening.

A single cell removed from the microscopic eight-cell embryo is amplified and analyzed to determine whether it is male or female.

The first children born after the screening process were twins, Natalie and Danielle Edwards. The girls, born two weeks ago, were five weeks premature but are healthy and growing, Handyside said.

The mother, Debbie Edwards, approached the Hammersmith Hospital team after learning she carried the gene for adrenoleukodystrophy, a fatal disease similar to muscular dystrophy, Handyside said.

Debbie’s sister also carries the gene and has an 11-year-old boy who was stricken at age 8 and is now totally disabled.

Six other couples have gone through the program and are expecting girls, Handyside said. The mothers carry the gene for any of 200 diseases, including hemophilia, Duchenne muscular dystrophy and adrenoleukodystrophy. All affect male children, Handyside said.

Traditional prenatal screening takes cells from the placenta in the first 8 to 10 weeks of pregnancy, and if genetic defects are detected a women can opt for an abortion.

Screening before an embryo is implanted reduces the risk of a woman becoming infertile after repeated abortions, Handyside said.

In addition, for families that risk passing on serious genetic disease to males, the embryo procedure should be less emotionally trying than an abortion, said Dr. Kathleen Nolan, a pediatrician and ethicist at the Hastings Center in Briarcliff Manor, N.Y.

Since no one had removed a single cell from a 3-day-old embryo before, Handyside said there were initial concerns.

“We had no direct evidence, but every animal and mammal we looked at was able to regulate for removal of cells at early stages,” the embryologist said.

Handyside said the embryo has a natural defense mechanism that allows growth to continue normally.

“It appears to be a response to damage which could happen in the reproductive tract,” he said.