The ABCB is a part of the ongoing Aarhus Birth Cohort, and contains data from the second trimester on time to pregnancy, lifestyle, medication use, previous pregnancies, education and working conditions. Data on birth outcomes are later added to the cohort. The ABCB includes presently 4000 “families to be” and each entry contains blood samples from the pregnant woman (and expectant father) taken early in pregnancy, and blood and umbilical cord tissues from their newborn baby.