Fetal Genome Screening Could Prove Tragic

In a few years you will be able to order a transcript of your entire genetic code for less than $1,000. Adults cannot do much to alter their biological lot, but what if parents could examine their unborn child's genome? Without proper guidance, they might decide to take drastic measures—even to end the pregnancy—based on a misguided reading of the genetic tea leaves.

Two different university laboratories have developed tests that will reveal the entirety of a fetus's genetic code using just a blood sample from the mother (or that sample plus a drop of saliva from the father). Prenatal whole-genome sequencing will provide volumes of information beyond the currently available tests for genetic disorders such as Down's syndrome or Tay-Sachs disease—assays that parents now use to decide how to respond to a pregnancy. The three billion units of code furnished in the new tests will also dwarf the relative trickle of information provided by consumer gene-testing services such as 23andMe, which currently look (postnatally) only at perhaps about one million locations in the genome.

Any woman who undergoes such...