MORRISVILLE, NORTH CAROLINA — Herasight Inc. has begun offering polygenic embryo screening at its lab in Morrisville, North Carolina, allowing prospective parents to select embryos based on predicted risks for thousands of diseases and odds for specific traits. The company analyzes saliva, blood and embryonic cell samples to generate polygenic risk scores that clients use to choose which embryos to use to try to have children.

The service estimates the chances that embryos will produce children at risk for illnesses ranging from rare inherited disorders such as Tay-Sachs and cystic fibrosis to common diseases with genetic factors such as cancer, heart disease, diabetes and Alzheimer's. Herasight, named after the Greek goddess associated with fertility, also predicts height, body mass index, longevity and IQ.

"These are saliva samples as well as blood," said Justin Schleede, a geneticist who serves as executive lab director at Herasight. "For people that are risk averse and don't want to simply roll the dice, they come to us to try to get as much genomic information to pick embryos for the purpose of having happy, healthy, disease-free children," he said.

Polygenic risk scores are numerical estimates based on genetic variants. Other companies operate in the same field, including Orchid Health of Palo Alto, California, which calculates only health risks, and Nucleus Genomics of New York, which allows prospective parents to select traits including eye color, hair color, propensity for baldness and acne, and handedness. Nucleus Genomics has advertised its service in a New York campaign.

Embryo screening services can cost as much as $50,000, in addition to thousands more for in vitro fertilization. Some clients undergo in vitro fertilization for infertility and have their embryos screened during the process, while others pursue it specifically to produce embryos for screening.

Christian Ward, a tax accountant who used embryo screening, cited diabetes as a concern. "It's really difficult to go from a healthy life to then being completely insulin dependent. It's just not something that I'd like to pass on to a child. I wouldn't want my child to be always thinking about their blood sugar and how to manage it," Ward said. He also described reviewing predicted physical traits during the process. "It's kind of trippy to think that you can kind of cycle through and see, 'Oh, this embryo could potentially have this hair color, this eye color,' all these other things," he said.

The American College of Medical Genetics and Genomics and the American Association of Reproductive Medicine have stated that the science of polygenic risk scores has not progressed enough to produce reliable estimates. Susan Klugman, a medical geneticist who served as president of the American College of Medical Genetics and Genomics, said the technology is unproven for embryos. "Polygenic risk scores for embryos are not yet ready for prime time. Polygenic risk scores for embryos are a new technology. And current evidence doesn't support their accuracy, their safety or their clinical value," Klugman said. She also raised the possibility of unintended trade-offs in trait selection. "While you are selecting for blue eyes, let's say, we don't know if you are also selecting for a certain disease or disorder. We just don't know," she said.

Polygenic risk screening for embryos is part of what has been termed the Gattaca Stack, which would combine such screening with embryo editing, artificial wombs and lab-grown eggs and sperm to create genetically enhanced humans.