New mothers with hepatitis B can safely breastfeed their babies, as long as they take a few important precautions, according to a new study.

The hepatitis B virus causes inflammation and swelling of the liver and can lead to chronic damage on the organ. The infection is spread through blood, unclean needles, and sex. It may also pass from a mother to her baby during pregnancy and labor.

It has been unclear whether breastfeeding may also transmit the virus, researchers say in the Archives of Pediatrics & Adolescent Medicine.

Their report, a review of past studies, allays those fears.

Even in mothers with the virus, “breastfeeding should be recommended as a valuable source of nutrition to infants,” study author Dr. Zhongjie Shi of Temple University in Philadelphia told Reuters Health in an email.

The researchers combined data from 10 previous studies, all conducted in China, which compared rates of hepatitis B in the babies of more than 1,000 mothers with the virus. About half of those mothers breastfed their babies.

To prevent transmission of hepatitis B from the mom, babies are given a vaccine and another injected medication soon after birth, and are vaccinated two or three more times during the first few months of life.

By their first birthday, 31 babies out of the 637 with breastfeeding mothers tested positive for hepatitis B. That compared to 33 babies out of 706 who had mothers who didn’t breastfeed.

Most of those infants, the researchers explained, had been infected with the virus during pregnancy or childbirth.

Shi said that blood is the easiest way for hepatitis B to travel from mother to baby, followed by amniotic fluid and vaginal secretions. He added that hepatitis B is up to 100 times more infectious HIV.

Moms should avoid breastfeeding if they have cracked or bleeding nipples or lesions on their breasts, the authors note, as that could be a way to transmit the virus more easily.

According to the World Health Organization, about 350 million people worldwide are living with chronic hepatitis B infection, while as many as 2 billion have been infected. About one in four people infected with the virus as a child ultimately die of liver cancer or liver scarring caused by the disease.

Shi concluded that while more studies on this topic are needed, the new results “are most valuable in developing countries and areas with high (hepatitis B) prevalence or heavy population, such as India, China, (and) south east Asia.”

SOURCE: Archives of Pediatrics & Adolescent Medicine, online May 2, 2011.