The twin girls were born in the northwestern region of Galicia last July and are the first in Spain to be screened for the mutated BRCA2 gene, which would have given them a high chance of developing breast cancer.
The mother of the twin girls chose to undergo the embryo screening treatment in the knowledge that her own great-grandmother, grandmother and mother had all died young from the disease.
"Without this I would not have had children as I wouldn't want to condemn them to living with the risk," the twins' mother, who has chosen to remain anonymous, told La Voz de Galicia newspaper.
The woman, who is in her mid-thirties, said that she has chosen to have a preventative mastectomy, a procedure that she is expected to undergo within three years.
Pre-implantation genetic diagnosis (PGD) involves taking a cell from an embryo at the eight-cell stage of development, when it is around three-days old, and testing it.
This takes place before conception - which is defined as when the embryo is implanted in the womb - when doctors select an embryo free from rogue genes.
In this case, the woman was given fertility treatment and of the 11 embryos produced, three were found to be free of the BRCA2 gene.
Two were implanted and both have resulted in healthy baby girls.
"With the genetic mutation they would have had a 60 percent likelihood of developing breast cancer," explained Elkin Muñoz, the gynecologist and fertility expert responsible for the case at the Instituto Valenciano de Infertilidad (IVI) in Vigo.
The screening process, which has been used previously in Spain to detect other inherited genes, had to be approved by the National Committee on Assisted Reproduction at Spain's Ministry of Health.
It was carried out privately "at a cost of between €14,000 - €15,000," she told La Voz de Galicia.