Cohort recruitment

COPSAC recruited pregnant women from greater Copenhagen, Denmark.

Eligibility criteria included mothers fluent in Danish and a physician's diagnosis of asthma and the need of daily treatment of asthma after the age of 7 years. 798 women were invited of whom 548 visited the COPSAC research unit to receive detailed information. Mothers of 452 infants consented to participation.

The infants were enrolled at a visit at one month of age. Exclusion criteria were failure to show up at this first visit, severe congenital anomaly, gestational age <36 weeks, and mechanical ventilation or lower respiratory tract infection prior to enrollment.

411 infants were enrolled in the cohort between Aug 1998 and Dec 2001.