WASHINGTON (CNN) -- Testing all pregnant women for the HIV virus could reduce the number of AIDS babies born and should become part of routine prenatal care, an independent advisory panel told Congress on Wednesday.

The Institute of Medicine report follows an extensive review of the best existing research and opinion on preventing mother to child transmission of HIV.

The recommendation is likely to be controversial.

AIDS expert say testing all women who become pregnant each year could further reduce the number of babies born with HIV.

Even though HIV testing is becoming more common, many doctors, including the American Medical Association, believe routine testing is not needed since a vast majority of pregnant women are not infected.

Of the more than 4 million women who become pregnant each year, just 8,000 are estimated to be infected with HIV.

Some fear inaccurate test results that show a woman is HIV-infected could cause unnessary stress.

"Without proper pre-test counseling ... there will be a lot of people unduly alarmed," said Dr. Michael Greene of Massachusetts General Hospital, a spokesman for the American College of Obstetrics and Gynecology.

Current federal HIV treatment guidelines advise doctors and other health care providers to give "extensive pre-test counseling to all pregnant women" and to help them understand the benefits of HIV testing.

However, many doctors who testified before the institute said counseling their patients on HIV is a burden and many don't do it.

Much can be done for a pregnant woman who tests positive for HIV. Taking the drug AZT can dramatically cut the chances she will pass on the virus to her child.

The use of AZT has cut the number of HIV infected babies born by 43 percent between 1992 and 1996.

"The message to women is, this is a disease for which we can do a great deal right now," said the chair of the study, Dr. Marie McCormick of Harvard University. "If you find you're positive, there's a great deal we can do to keep you healthy and, more importantly, to prevent transmission to your child."

In 1996, 1,600 babies where born with HIV, and the government says at least 432 babies were diagnosed with full-blown AIDS last year.

The Centers for Disease Control and Prevention said it will consider the recommendation, but that pregnant women would need to know some basic information on HIV before being tested.

The Institute of Medicine recommended the HIV test be included with other routine tests commonly given to pregnant women, such as the test for syphilis.

It did caution, however, that routine testing will not eliminate HIV births since AZT isn't foolproof and 15 percent of HIV-infected women don't seek prenatal care.

The Associated Press contributed to this report.