Hospital admissions for lower respiratory tract infections after early-, late-, and post-term birth.

BACKGROUND

Recent data suggest that early-term births are associated with later respiratory morbidity (LRTI), and post-term births may decrease this risk.

OBJECTIVES

The objective was to determine the impact of early-term, late-term, and post-term birth on hospital admission for LRTI up to the age of seven years. Additionally, we explored maternal and perinatal factors associated with the risk of admission for LRTIs.

METHODS

The association of early-term (37 -38  weeks), late-term (41 -41  weeks), and post-term (≥42 weeks) birth with hospital admissions for lower respiratory tract infections (LRTI) in comparison with infants born full-term (39 -40  weeks) was assessed and early predictors of LRTI were established. The register study included 948 695 infants born in Finland in 1991-2008. Data were analysed in four-term subgroups. Hospital admissions for bronchiolitis/bronchitis and pneumonia were collected up to 7 years of age. Adjusted Cox proportional hazards models were used to assess risk factors of LRTI admissions.

RESULTS

The rates of hospital admission in the early-, full-, late-, and post-term groups were 6.7%, 5.5%, 5.1%, and 4.8% for bronchiolitis/bronchitis, and 2.8%, 2.4%, 2.3%, and 2.3% for pneumonia. Early-term birth was associated with an increased risk of admission for bronchiolitis/bronchitis (hazard ratio HR 1.21, 95% confidence interval CI 1.18, 1.23) and pneumonia (HR 1.16, 95% CI 1.12, 1.20), while late-term (HR 0.93, 95% CI 0.91, 0.95) and post-term births (HR 0.89, 95% CI 0.85, 0.93) were associated with a decreased risk of bronchiolitis/bronchitis admission compared with the full-term group. Maternal age ≤ 20 years, smoking during pregnancy, male sex, caesarean delivery, small for gestational age, 1-minute Apgar score < 4, ventilator support, and neonatal antibiotic therapy were associated with an increased risk of LRTI admission, while being firstborn, born in a level-II hospital and in the Northern region was associated with decreased risk.

CONCLUSION

Early-term birth was associated with a higher risk of all LRTI admissions while late-term and post-term births were associated with lower risk of bronchiolitis/bronchitis admission. Modifiable risk factors of LRTIs were smoking during pregnancy, birth by elective caesarean delivery, neonatal ventilator support, and antibiotic therapy.