CHAMPAIGN, Ill. — Exposure to the phytoestrogen genistein prior to conception may adversely affect female fertility and pregnancy outcomes, depending on the dosage and duration of exposure, a new study in mice suggests.

Chronic preconception exposure to genistein affected pregnancy rates in mice and was associated with prolonged labor, smaller litters and pups, and higher rates of pup mortality, scientists at the University of Illinois report in a paper accepted for publication in the journal Reproductive Toxicology.