A girl due to be born next week will be the first British baby genetically selected to be free of a breast cancer gene.
She grew from an embryo screened to ensure it did not contain the faulty BRCA 1 gene, which passes the risk of breast cancer down generations.
Any daughter born with the gene has a 50% to 85% of developing breast cancer.
In June the 27-year-old mother now waiting to give birth told how she decided to undergo the screening process after seeing all her husband's female relatives suffer the disease.
The woman, who wants to remain anonymous, said: "We felt that, if there was a possibility of eliminating this for our children, then that was a route we had to go down."
The technique, known as pre-implantation genetic diagnosis (PGD) has already been used in the UK to free babies of inherited disorders such as cystic fibrosis and Huntington's disease.
But breast cancer is different because it does not inevitably affect a child from birth and may or may not develop later in life. There is also a chance it can be cured, if caught early enough.
Permission to carry out PGD for breast cancer had to be obtained from the Human Fertilisation and Embryology Authority by the London clinic which performed the procedure.
The body, which licenses IVF clinics and embryo research, gave the go ahead after holding a public consultation.
Fertility expert Paul Serhal, who led the PGD team, said: "We have now entered a new era of being able to help people who have cancer genes. Not only can we liberate people from the guilt of passing a cancer gene onto their child, we can cut off transmission of the gene once and for all. These are families who have been plagued by this genetic curse for generations. With a wave of a magic wand the job is done, and this is fantastic."
