A new UK study finds that babies born early, even by just a few weeks, tend to have higher risks of poor health in their early years, compared to those born full term. The study challenges the widely held view that the long term health outcomes for moderate and late preterm babies, even up to 37 or 38 weeks of gestation, are similar to those carried to full term.
The researchers, from the Universities of Leicester, Liverpool, Oxford, and Warwick and the National Perinatal Epidemiology Unit, write about their findings in a paper published online in the British Medical Journal on 1 March.
They write that their research is “the first large population based study in the UK to explore the relation between gestational age at birth and later health outcomes”.
For the study, first author Elaine M Boyle, senior lecturer in neonatal medicine in the Department of Health Sciences at the University of Leicester, and colleagues, analyzed data on over 18,000 British babies born between September 2000 and August 2001.
The data came from the Millennium Cohort Study (MCS), and includes health measures taken when the babies reached the age of nine months, three years, and five years.
These included assessments of growth such as height and weight (and BMI), longstanding illness/disability, wheezing/asthma, use of prescribed medications, hospital admissions, and parents’ rating of their children’s health.
The analysis showed that some measures (general health, hospital admissions, and longstanding illness) appeared to have a “dose-response” relationship to early birth, in that the earlier the birth, the higher the risk of a poorer outcome in these measures.
The greatest contribution to disease at the age of both three and five was being born moderate/late preterm (32-36 weeks gestation) or early term (37-38 weeks).
Both moderate/late pre-term and early term babies were re-admitted to hospital in their first few months of life more often than full term babies (39-41 weeks).
Babies born between 33 and 36 weeks of gestation, had an increased risk of asthma and wheezing compared to those born full term.
The researchers found that babies born at less than 37 weeks of gestation were more likely to have single mothers, with fewer educational achievements and less likely to be in managerial jobs.
Babies born very preterm were the most likely to have mothers who smoked and least likely to breastfeed for four months or longer, than babies born at 37 weeks or later.
The researchers conclude their results suggest that “health outcomes of moderate/late preterm and early term babies are worse than those of full term babies.”
“Irrespective of the reason for preterm birth, large numbers of these babies present a greater burden on public health services than very preterm babies,” they add.
The authors say it is inapprorpriate to group babies into preterm or term, because these findings show there is a “continuum of increasing risk of adverse outcome with increasing prematurity, even approaching full term gestation”.
They call for further studies to quantify how much of this effect is due to complications with the mother or the fetus, rather than prematurity itself.
Written by Catharine Paddock PhD