Aspiring Parents Have a New DNA Test to Obsess Over

The first time Jamie Cassidy was pregnant, the fetus had a genetic mutation so devastating that she and her husband, Brennan, decided to terminate in the second trimester. The next time they tried for a baby, they weren’t taking chances: They would use IVF and screen their embryos’ DNA. They wanted to avoid transferring any embryos with the single-gene mutation that had doomed their first pregnancy. And then they started wondering what other ailments they could save their future son or daughter from.

The Cassidys’ doctor told them about a company, Genomic Prediction, that could assess their potential children’s odds of developing conditions that aren’t tied to a single gene, such as heart disease, diabetes, and schizophrenia. The test wouldn’t be any more invasive than screening for a single gene—all the company needed was an embryo biopsy. The science is still in its early stages, but the Cassidys didn’t mind. Brennan has Type 1 diabetes and didn’t want to pass that condition on, either. “If I can forecast that my baby is going to have less chance to have Type...