Investigators from NCI, Norway, and the United Kingdom are examining maternal, gestational and neonatal factors in relation to breast tumors by pooling data from the Norwegian Mother and Child Cohort Study (MoBa) with those from the ALSPAC (Avon Longitudinal Study of Parents and Children) cohort to evaluate epidemiological risk factors and whether conCentreations of angiogenic proteins and hormones influence the risk of breast cancer in mothers.