A population-based study of the health and developmental consequences of preterm birth
While there is a growing body of literature describing health outcomes in very preterm babies, few studies have focused on outcomes in moderately preterm babies (i.e. gestation of 32-33 weeks) or late preterm babies (i.e. gestation 34-36 weeks). These groups of babies represent a relatively large proportion of births, and therefore, even modest increases in health problems may have important implications for public health and for the allocation of health and educational resources. The aim of this study was to describe gestation-specific effects on a range of child health and, cognitive and developmental outcomes measured at age 3 and 5 years in a national cohort study (the Millennium Cohort Study). Babies born at all gestations were included, and the analysis describe effects according to gestation in weeks, gestation in broader groups (23-31, 32-33, 34-36, 37-38, 39-41 weeks).
For all of the outcomes we assessed (health, behaviour, cognitive development and school performance), our study found that the risk of problems increased with prematurity, and for most outcomes there was an increased risk even in children born late preterm (34-36 weeks) or early term (37-38 weeks) compared with children who were born at full term (39-41 weeks). For example:
- There was an increased risk of the child having a longstanding illness at age 5 years if they were born late preterm (OR=1.5) or early term (OR=1.1) compared with children born at full term.
- There was an increased risk of the child having at least hospital admissions between age 9 months and 5 years if they were born late preterm (OR=1.9) or early term (OR=1.4) compared with children born at full term.
- There was an increased risk of the child having poorer school performance at age 5 years if they were born late preterm (RR=1.12) or early term (RR=1.05).
- These effects were consistent across a range of health and developmental outcomes.
- These effects, though relatively small, potentially affect a large number of children - about 21% of all births are early term and 6% are late preterm.
There have recently been a number of papers published showing outcomes in children who were born late preterm or early term. Therefore, we have conducted a systematic review of the effects of late preterm and early term birth on child cognitive development. We are also conducting further analysis of the Millennium Cohort Study to determine whether the effects on school performance at age 5 persist at age 7.