Infants born very prematurely can require supplementary oxygen for many months. Rehospitalisation is common in the first 2 years after birth and the majority of admissions are for respiratory disorders. Rehospitalisation is particularly increased in infants with bronchopulmonary dysplasia (BPD) who require supplementary oxygen for more than 28 days after birth, and in infants who have a respiratory syncytial virus (RSV) lower respiratory tract infection (LRTI) (see chapter 16). Respiratory symptoms continue to be common in schoolchildren who were born prematurely, and the most severely affected remain symptomatic in adulthood; an adverse outcome that may be more common in females. Prematurely born infants, particularly those who wheeze at follow-up, have evidence of airway obstruction (raised airway resistance and gas trapping) in the first 2 years after birth. Their lung function improves with increasing age, but even in adolescence there is evidence of airflow limitation in those who had had BPD, particularly in those with ongoing recurrent respiratory symptoms. Gas transfer abnormalities and airway hyperreactivity have also been described, and fixed airway obstruction has been reported in young adults who had severe BPD.

It is more than 20 years since it was first reported that airway function was diminished in adults born with low birthweight and it was speculated that pre-natal nutrition might program fetal lung growth. Low birthweight, however, is only one of a number of early-life factors that might influence respiratory disease in children and adults; other factors potentially include breastfeeding, post-natal weight gain, maternal paracetamol use during pregnancy, maternal obstetric complications, and indoor and outdoor air quality. This chapter will focus on the major risk factors.