While having hepatitis B increases the odds of developing liver cancer, the risk is reduced in women who’ve had several pregnancies, a study suggests.

There’s a relative dearth of long-term studies of hepatitis B virus (HBV) infection and liver cancer in women as opposed to men, Dr. Chien-Jen Chen, from the Genomics Research Center in Taipei, Taiwan, and his associates note in the Journal of the National Cancer Institute.

To identify risk factors for liver cancer among women, Chen’s team examined data from close to 1.8 million pregnant women who were tested for HBV. During an average follow-up of 8 years, 306 women were diagnosed with liver cancer.

The researchers found that women who tested positive for HBV were up to 17 times more likely to develop liver cancer. However, this risk was modified by the number of prior pregnancies.

Liver cancer incidence rates per 100,000 women per year were 2.04 for women with one child, 1.55 for those with two, and 1.66 for those with three or more children, Chen and colleagues report.

They say the underlying biological reasons for this reduced risk “merit further investigation.”

SOURCE: Journal of the National Cancer Institute, July 15, 2009.