Newborn's Weight May Affect Adult Cancer Risk

An infant's birth weight may predict cancer risk later in life, a new study shows.

A study in the Feb. 7 International Cancer Journal found that heavier birth weight babies were more likely to have cancer of the stomach, pancreas and colon, and more likely to have blood-cell cancers, compared to infants born at lighter weights.

Heavier newborn girls have a higher risk of developing breast cancer before age 50, says the study. The findings came from British and Swedish researchers including Valerie McCormack of the London School of Hygiene & Tropical Medicine (search).

The risk of developing cancer was not the same for all types of cancers. Infants born at a higher birth weight had a lower risk of developing cancer of the lining of the uterus (endometrial) later in life.

Other cancers — including ovarian, cervical, and prostate cancer — weren't affected by birth weight.

Data came from more than 11,000 babies born at Sweden's Uppsala Academic Hospital (search) from 1915 to 1929. The hospital kept detailed records on each baby, including birth weight, maternal age, birth order, length and head circumference.

When the babies became 37-year-old adults, British and Swedish researchers began monitoring their health records for cancer, following them for about 40 years. During that time, 2,685 cancers were registered for the group.

The researchers calculated the difference each extra pound (450 grams) at birth made for adult- cancer risk. They factored in differences due to smoking and variations in the number of weeks of pregnancy at the birth of each infant.

Every extra pound at birth brought a 13 percent increase in digestive cancers, a 17 percent increase in blood cell cancers, and a 39 percent increase for breast cancer in women before age 50.

For men, cancer risk rose 8 percent for every 450-gram increase in birth weight. For women, increased cancer risk rose until age 50, mainly due to breast cancer.

However, heavier newborn girls had an advantage with cancer of the uterine lining (endometrial cancer). They were 24 percent less likely to have endometrial cancer, regardless of age.

"Rates of this cancer in women who weighed at least 4,000 grams (8.32 pounds) were almost half that of women who weighed under 3,000 grams (6.2 pounds)," write the researchers.

McCormack and colleagues aren't sure how to explain the findings. Perhaps larger birth size means more cells at risk for cancer, as some studies have suggested.

Still, smaller babies don't have all the advantages. In addition to the increased endometrial cancer risk, the researchers say that other studies have linked smaller birth size to increased risk of heart disease and diabetes later in life.

There's no way to change your birth weight. But being active, following a nutritious diet, and getting proper medical care can help your health, whether you were a big baby or a petite newborn.

By Miranda Hitti, reviewed by Brunilda Nazario, MD

SOURCES: McCormack, V., International Cancer Journal, Feb. 7, 2005; vol 115. News release, John Wiley & Sons, Inc.