Predictive effects of low birth weight and small for gestational age status on respiratory and nutritional outcomes in cystic fibrosis

Abstract

Introduction: Prior literature shows that neonates with cystic fibrosis (CF) are more likely to be born low birth weight (LBW, <2500 grams) and/or small for gestational age (SGA, <10^th percentile for weight) than non-CF counterparts. There is limited literature exploring the predictive effects of birth parameters on long-term outcomes.

Methods: The study population (CF Twin and Sibling Study) was recruited between 2000-2013 (n = 1677). Relationships between FEV₁ percent predicted at 6, 12, or 18 years or BMI z-score at 2, 6, 12, or 18 years, and predictor variables (LBW or SGA status) were assessed using adjusted linear regressions.

Results: Mean birth weight was 3.3 ± 0.7 kg (Females: 3.2 ± 0.7kg; males: 3.4 ± 0.7kg) and mean gestational age was 38.4 ± 2.6 weeks, with 10.2% of participants classified as SGA. Predictors of LBW included female sex, pancreatic insufficiency, and prematurity. Predictors of SGA included female sex. After adjustment, LBW was associated with lower BMI at ages 2-12 years and SGA was associated with lower BMI at age 2 years. LBW was associated with lower FEV₁ percent predicted only at age 6 years. SGA was not associated with FEV₁.

Conclusions: We did not observe higher rates of LBW or SGA in full term infants compared to the general population. We observed associations particularly between LBW and BMI or FEV₁, but these associations decreased with age, suggesting that alternate factors contribute to outcomes over time. In lieu of the ability to target growth during gestation, efforts could be considered to optimize infant nutritional status, which may improve later life outcomes.

Keywords: BMI; Cystic fibrosis; FEV1; birth weight; gestational age; neonate.