Association between chorioamnionitis and early childhood asthma among low-birthweight infants

Background: We explored the association between chorioamnionitis and childhood asthma among low-birthweight preterm infants.

Methods: We used the Matched Perinatal Service System, Hospital Inpatient, and Physician encounter datasets for all KPSC facilities (1991-2006) to identify 31,529 of preterm born infants who remained KPSC members for ≥3 years after delivery. The outcome was physician-diagnosed asthma in the first 3 years of life. Birthweight was categorized as very-low-birthweight [VLBW; <1500g], moderately-low-birthweight [MLBW; 1500-2499g], and normal-weight [NBW; ≥2500g]). The exposure was a history of chorioamnionitis.

Results: The rate of infants who had perinatal exposure to chorioamnionitis was 4.9%. Asthma prevalence in children aged ≤3 years was 14.1% (n=4,435). Compared to infants without chorioamnionitis, infants with chorioamnionitis were at increased risk of asthma in the first 3 years of life (OR 1.9; 95% CI 1.6-2.1). VLBW (OR 1.5; 95% CI 1.2-1.8) and MLBW (OR 1.4; 95% CI 1.1-1.7) infants with chorioamnionitis were at increased risk of asthma compared to similar birthweight infants without chorioamnionitis, but not NBW infants (OR 1.1; 95% CI 0.8-1.4). African-American and Hispanic VLBW and MLBW infants with chorioamnionitis were at increased risk of asthma, but not Asian/Pacific Islander infants. We also observed a significant association between chorioamnionitis and childhood asthma among MLBW Caucasian infants.

Conclusion: Chorioamnionitis may be an important risk factor for childhood asthma. We speculate that the association between LBW and childhood asthma may be mediated by chorioamnionitis causing fetal lung inflammation and injury leading to compromised airways.