The researchers therefore evaluated the diets of women 12 months before they became pregnant, assuming that their diet during this period reflected their diet during pregnancy.

Included in the study were 138 babies with acute lymphoblastic leukemia (ALL) born in northern California between 1995 and 1999, and 138 infants without ALL that were matched by gender, date of birth, mother's race, Hispanic ethnicity and county of residence. The findings are presented in the journal Cancer Causes and Control.

Vegetable, fruit and protein consumption were inversely proportional to the child's risk, Jensen's group found.

Specifically, carrots, string beans, peas, cantaloupe, beans and beef were foods associated with reduced risk. The specific dietary nutrients included provitamin A carotenoids and alpha and beta-carotene.

"These findings show how vital it is that women hoping to get pregnant, as well as expectant moms, understand that critical nutrients in vegetables, fruit and foods containing protein, such as meat, fish, beans and nuts, may protect the health of their unborn children," Jensen said in a National Institutes of Health press release.