METHODS
Population and study
procedures
The details of this birth cohort (NCT02903134) have been published
elsewhere7. Briefly, pregnant women were recruited
during their stay in the delivery ward in Santiago, Chile, after consent
was obtained. Information collected included parental sociodemographic,
home characteristics, and perinatal characteristics of the offspring, as
previously described7. Cord blood was collected,
processed as previously described7, and stored for
analysis. Children were followed by phone every 6 months through age 24
months, and in-person at age 30 months. At each visit information was
collected about feeding characteristics, pets, second-hand tobacco
smoking, acute respiratory illnesses, siblings, day care attendance, as
well as physician diagnosis of asthma and other atopic diseases. Any
diagnoses of asthma and their treatment was made independently by the
participants’ primary care providers (PCPs), who were not part of the
current study. The Edinburg scale for maternal depression postdelivery
was performed at 6 months. The study was approved by the Ethics
Committees of the participating institutions.
Our primary outcome was
physician-diagnosed asthma during the first 30 months (made
independently by the PCP not involved in the study).
The main risk factor evaluated was
a positive API (API+) according to the original stringent
criteria: children had to be
defined as an early frequent wheezer (more than 3 episodes) during the
first 3 yr of life and meet at least one of two major criteria (parental
MD asthma or MD eczema in the child) or two of three minor criteria (MD
allergic rhinitis, wheezing apart from colds, or
eosinophilia)5.
The API was constructed at the end
of this study by us, independently, and blinded to the main outcome of
physician-diagnosis asthma made by the PCP not involved in the study.