While many countries have moved in recent years to impose boundaries on assisted reproduction, the U.S. fertility industry remains largely unregulated and routinely offers services outlawed elsewhere. As a result, the United States has emerged as a popular destination for IVF patients from around the world seeking controversial services — not just sex selection, but commercial surrogacy, anonymous sperm donation and screening for physical characteristics such as eye color.

This freewheeling approach has been good for business; the U.S. fertility industry is estimated to be worth as much as $5.8 billion this year. But as technological advances outpace any social consensus on such forms of reproductive intervention, discomfort with the hands-off status quo is rising.

Last month, news that a U.S.-educated Chinese researcher had created the world’s first gene-edited infants reignited a debate over the morality of “designer babies.” Some scientific leaders blasted the effort, which purported to make the babies resistant to HIV infection, and urged the U.S. government to step in.

National Institutes of Health Director Francis Collins ... said he also is concerned about the rise in the screening of embryos for characteristics such as intelligence, physical appearance and gender. Although editing a baby’s DNA is fundamentally different from picking and choosing among embryos created by nature, the procedures raise similar ethical questions about ma­nipu­la­ting human reproduction. ...

A survey published in March in the Journal of Assisted Reproduction and Genetics found that nearly 73 percent of U.S. fertility clinics offer gender selection. Of those, nearly 84 percent offer it to couples who do not have fertility problems but are considering IVF solely to control the pregnancy’s outcome. ...

Jeffrey Steinberg, a fertility specialist in Encino, Calif., ... says would-be parents are starting to demand even more screening options. He estimates that he has helped 70 couples screen for eye color (the success rate is about 60 percent — a little better than a coin flip) and is working with 20 more. Blue is the most-requested color, followed by green.

“People call up asking for all kinds of things: Vocal ability, athletic ability. Height is a big one. I have a lot of patients who want tall children,” he said.

So far, Steinberg and other fertility specialists have not been able to identify the genes that drive those traits. But he believes they will be found. And when that happens, he will offer to screen for them.

“If you do what I do, you can’t have a strong ethical opinion,” he said, unless parents ask for “something that is going to be harmful.”

The technology is moving fast. One biotechnology company, Myome, says it will soon offer couples undergoing IVF the ability to identify embryos most likely to grow into healthy adults by calculating their risk of a wide spectrum of diseases and disorders. Another company, Genomic Prediction, is rolling out an intelligence screening service that it says will help parents identify and reject embryos with a higher risk of growing into a children with lower IQs.