A controversial screening technique called pre-implantation diagnosis (PGD) has made it possible for a British woman to conceive a baby guaranteed to be free from hereditary breast cancer.
Doctors rejected six embryos that tested positive for the cancer gene and selected "healthy" ones to ensure the child would not contract the killer disease.
The 27-year-old woman, who wishes to remain anonymous, is now 14 weeks pregnant following implantation of the selected embryos.
The woman said she opted for the invasive IVF treatment because the breast cancer gene was hereditary in her husband's family. The woman's husband had tested positive for the gene and his grandmother, mother, sister and cousin had all battled breast cancer.
She said: "For the past three generations, every single woman in my husband's family has had breast cancer, as early as 27 and 29. We felt that, if there was a possibility of eliminating this for our children, then that was a route we had to go down."
"It has been successful which means we are eliminating the gene from our line. If we'd had a daughter with the gene and she was ill, I couldn't look her in the face and say I didn't try," she added.
Tests on the couple's 11 embryos involved extracting a single cell and were done when they were just three days old.
Of the11 embryos, 6 were found to have the gene, 2 of the five "healthy" embryos were implanted, leading to a single pregnancy, and 2 have also been frozen for future use.
Critics call this practice unethical because viable embryos are destroyed in the process. They also fear it could lead to the creation of "designer babies" that are chosen for their good looks or superior intelligence.
According to doctors, a girl conceived naturally by the couple from an embryo containing the hereditary gene, called BRCA-1, would have a 50 to 85 per cent chance of being affected by breast cancer.
In Britain alone more than 2,000 breast cancer cases are diagnosed each year and are thought to be caused by either the BRCA-1 or BRCA-2 genes. Both these genes can be detected in the embryos.
Many women who test positive for either of the genes are known to go through a mastectomy to avoid developing the disease later in life.
The couple's doctor, Paul Serhal, medical director of the Assisted Conception Unit at University College London Hospital, said: "Women now have the option of having this treatment to avoid the potentially guilty feeling of passing on this genetic abnormality to a child. This gives us the chance to eradicate this problem in families."