The study was a cohort study with a convenience sample of 1765 pregnant women from the population of all women in Iceland who gave birth in the period from August 2009 to November 2010.
Í ferilhópnum var hentugleikaúrtak 1765 barnshafandi kvenna úr þýði allra kvenna á Íslandi sem fæddu barn sitt á tímabilinu ágúst 2009 til nóvember 2010.