A woman with a rare genetic mutation that almost always results in early onset Alzheimer's disease has given birth to a child who, thanks to a new screening technique, does not carry the gene mutation, according to researchers at the Reproductive Genetics Institute in Chicago.

The mother carries the genetic mutation V717L, which is linked to a form of Alzheimer's disease that manifests itself in people as young as mid to late 30s. Two of the mother's siblings also carry the mutation. One of them developed Alzheimer's at age 38 and is now in an assisted living facility.

The mother underwent in vitro fertilization to become pregnant. Before implantation, the embryos used for the procedure were screened for the mutation and only embryos free from the genetic defect were implanted.

The screening technique, called preimplantation genetic diagnosis (PGD), has been used to detect other conditions such as Tay-Sachs and sickle-cell anemia, but this was the first use of the procedure to keep a child from being born with early onset Alzheimer's disease.

Some experts are questioning the ethics of the procedure, especially since the baby's mother, age 30, is likely to develop Alzheimer's disease while her child is still young. The mother, a geneticist, is currently pregnant again, having undergone another round of PGD.

The early onset gene is very rare, occurring in only about a dozen families worldwide. The affected carriers are almost guaranteed to develop early onset Alzheimer's disease.

Other sources: Journal of the American Medical Association, AP