Late preterm and small for gestational age – double the risk?

Late preterm infants born after 34 + 0 and before 37 + 0 weeks of gestation account for more than 75% of all preterm births so any problems they may have represent a sizeable healthcare burden. It is increasingly recognised that they can suffer greater acute and chronic respiratory morbidity than infants born at term. In a single centre study of 1022 infants, the need for respiratory support was 32%,18% and 11% in infants born at 34, 35 and 36 weeks of gestational age respectively and for supplemental tube feeding was 55%, 24% and 8% respectively. 1 Amongst 1,650,450 infants born between 35 and 41 weeks of gestation between 1998 and 2016, the risks for respiratory, severe neonatal, infectious and neurological morbidities were highest at 35 weeks and gradually decreased until 39 weeks. 2 The results are influenced by ethnicity. In our single centre study Black late preterm infants less frequently needed invasive and non-invasive ventilation and had a shorter duration of length of stay (LOS). 3 Late preterm infants have a higher rate of readmission. 4 They have an increased risk of RSV infection and asthma at 18months and more wheeze and nocturnal cough at school age. 5 In a national cohort of 4,079,878 singletons born in Sweden between 1973 and 2013-4, of whom 14.9% were diagnosed with asthma, the late preterm individuals had 1.31 increased risk of asthma. 6 They also may have poorer lung function at follow-up, 7 particularly if exposed to passive smoking. At three to seven years those born late preterm had worse forced oscillometry results indicating increased peripheral airways resistance, particularly if they had been hospitalised for pulmonary infection and had passive smoke exposure. 8