Rob Stein

A Swedish biologist wants to change the genes of healthy human embryos to find ways to treat infertility and other diseases. The experiments intensify ethical questions about genetic engineering.

Clinics are using stem cells to treat problems ranging from arthritis and torn tendons to paralysis and stroke. But researchers say there's no evidence that the treatments work or are safe.

The Centers for Disease Control and Prevention expanded its advice to travelers, advising pregnant women to avoid parts of Miami Beach where the Zika virus is spreading.

Though they're generally safe, strollers and baby carriers are associated with thousands of trips to the emergency room for very young children. Falls are more common than you might think.

The National Institutes of Health is proposing to fund experiments that create chimeras of human and animal cells while also imposing restrictions in response to ethical concerns.

The National Institutes of Health is proposing to permit funding for the controversial experiments, which involve scientists using human stem cells to create embryos that are part human, part animal.

The microbes that inhabit our bodies evolved with us for millions of years, providing new evidence of the symbiotic role our bacteria play in our lives.

The Florida Department of Health says it's possible that a Zika infection in Miami-Dade County is not related to travel in a country where Zika is spreading. An investigation is underway.

Each twin had an ovary removed and frozen in 2009, when they were in their 30s, in hopes of buying more time to get pregnant and have babies. But will the thawed, reimplanted ovaries work?

Federal and Utah health officials are investigating a case that may be the first instance of Zika spreading from one person to another in ways other than via mosquito bites, sex or the placenta.

A woman in her 20s infected a man after she returned to New York City from a country where Zika is spreading. Health officials say he got infected through unprotected sexual intercourse.

The Obama administration's controversial proposal to revise human research rules is flawed and should be scrapped, says a report from the National Academies of Sciences, Engineering, and Medicine.

A technology known as a gene drive might be deployed to re-engineer species and stop diseases like malaria. But a scientific advisory panel says research and use should proceed with great caution.

A synthetic version of the human genetic blueprint might used for a wide range of medical research, scientists say. But it's far from reality, and comes with big ethical and safety questions.

At least one U.S. hospital is attempting uterine transplants for women born without a uterus, or who've lost it to disease. The surgery has yielded births in other nations, but poses real risks, too.

Doctors are reporting the first case in the U.S. of a bacteria that is resistant to antibiotics often used as a last resort. The germ was found in a 49-year-old Pennsylvania woman with a urinary tract infection.

Researchers experimenting with chimeric embryos say they could develop into adult pigs, sheep or cows with human organs that one day might be suitable for transplantation in people.

The Food and Drug Administration has issued sweeping regulations that for the first time assert federal authority over electronic cigarettes, which have become increasingly popular, especially among young people.

The Food and Drug Administration released long-awaited plans Thursday. In addition to barring sales of tobacco products and e-cigarettes to people under age 18, the agency imposes other restrictions.

Scientists have been able to keep human embryos alive twice as long as before. The technique is reopening a debate over a rule limiting research on human embryos to 14 days.