The nation's largest doctors' group this week adopted new ethical guidelines for how physicians should talk to pregnant patients about donating their babies' umbilical cord blood.

The American Medical Association voted during a two-day meeting in Hawaii to encourage mothers wishing to donate to give the blood to public cord blood banks.

The stem cells in cord blood have the potential to save lives.

They're the same stem cells that make up the bone-marrow transplants that help many people survive certain cancers and other diseases. But cord blood is more easily transplanted into unrelated people and can be thawed at a moment's notice, giving it advantages over bone marrow.

"Umbilical cord blood stem cells are useful for some therapeutic purposes and as a potential source of stem cells," board member Dr. William A. Dolan said in a statement Monday. "Physicians should be prepared to discuss cord blood banking options with their patients during pregnancy."

About 50,000 cord blood donations are stored in more than 20 public banks around the country.

The National Cord Blood Inventory aims to triple that number so that almost everyone who needs stem cell treatment may find a match.

The American Medical Association's new ethical guidelines said doctors will ideally obtain their patient's consent to donate the baby's cord blood before the mother goes into labor.

Doctors should also disclose any ties they have to a cord blood bank, the guidelines said.

Further, doctors should never accept fees for a referral to a chord bank, the association said.

The American Academy of Pediatrics earlier this year issued its own set of guidelines on the issue.

Those urge more parents to donate their babies' cord blood.

The pediatricians' group also addresses whether patients should keep the cord blood in a private bank for their child's own if they should donate the blood to a public bank.

The academy concluded parents should consider private storage only if an older sibling has cancer or certain genetic diseases that cord blood is proven to treat.

Otherwise, they should consider donating their child's cord blood to a public bank.

The academy said a child has only between one in 1,000 and one in 200,000 chance of needing an infusion of his or her own cord blood later in life.

Separately, the American Medical Association said it would support routine HIV testing while continuing to advocate for the protection of patient privacy.

"AMA's new policy calls on physicians to routinely test consenting adult patients for HIV," board member Dr. Ardis Hoven said in a statement.

The doctor said HIV patients can lead full and productive lives if their infections are detected early.