Women from deprived backgrounds 50% more likely to have very premature babies, study finds

Babies treated in Irish neonatal units have short-term outcomes that compare well with the best international centres in the world. File photo

Women from deprived backgrounds in Ireland are 50% more likely to have a very premature baby, according to a new study.

But once babies are born, health outcomes are similar regardless of postcode.

The research team examined more than 80,000 births — around 27% of all deliveries in Ireland — at the National Maternity Hospital in Holles Street and the Rotunda Hospital between 2018 and 2022.

Of around 1,060 babies born before 32 weeks, 912 were examined in detail after exclusions such as missing address data and major congenital conditions.

The study found women from deprived backgrounds were 50% more likely than average to give birth more than two months early, while women from more affluent areas were 39% less likely to have a baby before 32 weeks.

“This study is the first to show that families from socioeconomic deprived areas are at higher risk of very pre-term birth in the Irish healthcare system,” said the authors.

However, differences in outcomes between babies from different backgrounds disappeared after birth.

“Reassuringly, while the odds of pre-term birth were higher in parents from socioeconomically deprived areas, the odds of many of the acute outcomes of pre-term birth of greatest concern were equivalent across the socioeconomic (spectrum),” said the study.

It added that this suggests that care and short-term outcomes of premature babies “transcends any potential socioeconomic adverse effects once pre-term delivery had occurred”.

The babies had an average gestational age of around 29 weeks and an average birth weight of about 1.2kg or just over two and a half pounds. Just over half (53%) were male, while just under a third were twins or from multiple pregnancies.

Spontaneous pre-term labour accounted for the largest share of early deliveries (42%) followed by pre-eclampsia at 14%. Over half of babies required mechanical ventilation, with around 40% developing chronic lung disease and just under 12% dying.

Causes and comparisons with other countries

The study author, Dr Daniel O’Reilly, a paediatric intensive care specialist registrar (SpR) at Children’s Health Ireland at Crumlin, said the causes were unclear.

“It is difficult to disentangle from the data we have collected what the exact cause of increased pre-term birth rates were in socioeconomically deprived areas.

“But they are likely a combination of environmental exposures based on data collected in other countries — (including) poor diet, increased exposure to pollutants and overcrowded housing environments."

Dr O’Reilly, an Irish Clinical Academic training fellow, was surprised by the study’s findings, published in the Journal of Perinatology.

“My actual working theory, when I started off with this, is that we'd see something that looked a bit more like a J-shaped curve, you would have a higher incidence of pre-term birth in the disadvantaged population, it would even out for an average population.

“And then slightly increase again in the affluent population due to older maternal age and an increase in assisted reproductive technologies, but we didn't see that.

“The other thing I thought was, maybe the differences won't be that stark in the Irish population, because we've more equality of access compared to somewhere like the US, but when you look at it, we have similar issues with increased pre-term birth in areas of relative deprivation.” 

The study says babies born at less than 32 weeks are a small population but require high levels of care.

“(They) are at high risk of unique complications of prematurity such as intraventricular haemorrhage and chronic lung disease (and) bronchopulmonary dysplasia. These conditions in turn are associated with a higher incidence of adverse neurodevelopmental outcomes.” 

Neonatal care

But Dr O’Reilly said babies treated in Irish neonatal units have short-term outcomes that compare well with the best international centres in the world.

The paediatrician added that overall mortality in similar cohorts in the UK, USA and Scandinavia is slightly higher than the rates in the Irish study, while the incidence of severe brain bleeds in the Irish study was lower than in other studies.

Due to the high-quality neonatal care in Ireland and the relative rarity of serious complications, he said differences between groups from different economic backgrounds may be difficult to detect.

Dr O’Reilly cautioned that his study only looked at short-term outcomes, but further research is under way.

“We only looked at acute outcomes in this study,” he said. “One of my colleagues is working on following how much these babies have been followed up, to see how they do from a developmental standpoint in the long term.” 

He noted that the economic status of parents could play a role in access to services in the long term for babies born prematurely.

“If there's a disproportionate amount of pre-term babies in those communities, I think it's important long term that people think about that, especially when we think about all the issues around caring for children with disabilities and additional needs more widely.” 

He said families in more deprived areas may face longer waiting times for services, while those who can afford private care may be able to access support more quickly.