Designer Babies: Human cloning is a long way off, but bioengineered kids are already here.

In the mid-1990s, embryologist Jacques Cohen pioneered a promising new technique for helping infertile women have children. His technique, known as cytoplasmic transfer, was intended to "rescue" the eggs of infertile women who had undergone repeated, unsuccessful attempts at in vitro fertilization, or IVF. It involved injecting the cytoplasm found inside the eggs of a fertile donor, into the patient's eggs.

When the first baby conceived through cytoplasmic transfer was born in 1997, the press instantly hailed Cohen's technique as yet another technological miracle. But four years later, the real story has proven somewhat more complicated. Last year, Cohen and his colleagues at the Institute for Reproductive Medicine and Science of St. Barnabas, a New Jersey fertility clinic, set off alarm bells among bioethicists with the publication of a paper detailing the genetic condition of two the 17 cytoplasmic-transfer babies born through the clinic to date. The embryologists reported that they had endowed the children with extra bits of a special type of genetic material, known as mitochondrial DNA, or mtDNA, which came with the cytoplasm transferred from the donor...