Parents or Gods?

The birth of Louise Brown in 1978, and with her that of human in vitro fertilization (IVF), was a landmark in medical science. Surgically harvesting eggs from a woman's ovaries, fertilizing them outside her body, and transferring the resulting embryos into her uterus enabled effective treatment of female infertility caused by irreparably damaged fallopian tubes. Since then, rapid innovation has led to new applications for IVF and other assisted reproductive technologies.

Many infertile couples now turn to such advanced technologies when other "low tech" options fail, and they are the treatment of choice not only for tubal damage, but also for significant forms of male infertility. For example, intracytoplasmic sperm injection is a technique in which a single viable sperm is injected into an egg, allowing fertilization to occur even in cases where few healthy sperm are available. Freezing unimplanted embryos is now standard procedure; freezing unfertilized eggs is under development.

Perhaps inevitably, our access to human eggs and embryos now enables us to extend prenatal genetic diagnosis to the pre-implantation embryo. Conventional prenatal diagnosis entails removing fetal cells, either from the amniotic fluid (amniocentesis) or from the placenta (chorionic villus sampling, CVS). Both procedures are routinely offered to pregnant women 35 years and over to diagnose chromosomal abnormalities such as Down's syndrome, or to screen for cystic fibrosis, sickle cell disease, or Tay Sachs disease.