Mortality risk amongst very low birth weight infants born in the Republic of Ireland, 2014-2016

Mortality risk amongst very low birth weight infants born in the Republic of Ireland, 2014-2016

Paul Corcoran (1), Sara Leitao (2), Anne Twomey (3), Brendan Murphy (3)

(1) Researcher Epidemiologist, National Perinatal Epidemiology Centre, University College Cork; (2) Researcher, National Perinatal Epidemiology Centre, University College Cork; (3) Consultant Neonatologist, National Maternity Hospital

Background
Globally, there are approximately six million deaths of children under 5 years of age each year, the leading cause of which is preterm birth complications. Very preterm infants are at especially high risk of mortality. The Vermont Oxford Network (VON) is a non-profit voluntary collaboration of health care professionals from nearly 1000 neonatal intensive care units around the world and it maintains a database of information regarding the care and outcomes of high-risk newborn infants.
We aimed to use the VON data to assess whether very low birth weight (VLBW) infants born in Ireland in 2014-2016 had a higher than expected risk of death.

Methods
Since 2014, all 19 neonatal units in Ireland have contributed data to the VON database on VLBW infants, defined as an infant who is born alive and whose birth weight is between 401 and 1500 grams OR whose gestational age is between 22 weeks 0 days and 29 weeks 6 days (inclusive). VON colleagues use multivariable logistic regression models to quantify the risk of mortality associated with a range of infant characteristics. We used coefficients from these regression models to calculate standardised mortality ratios (SMRs).

Results
The VON database had data on 1,812 VLBW infants born in Ireland in 2014-2016, of which 1,765 were records from their hospital of birth. The mortality risk for these 1,765 infants was 1.17 times higher than expected, a statistically significant excess mortality (95% CI: 1.05, 1.29). Infants born at 22-23 weeks had a 23% higher mortality risk (SMR=1.23, 95% CI: 1.02, 1.44) that was almost wholly due to the infants not administered resuscitation. Infants born at 24-27 weeks in a tertiary unit did not experience higher than expected mortality (SMR=1.01, 95% CI: 0.80, 1.23) but those born in non-tertiary units had a 70% higher mortality risk (SMR=1.70, 95% CI: 1.25, 2.15).

Conclusions
These findings support the recommendations that resuscitation should be administered to all infants born at 23 weeks who present in favourable condition, i.e. without congenital anomaly, severely small for gestational age, severe hypoxia or severe infection. In line with the existing Model of Care for Neonatal Services in Ireland, infants born before reaching a gestational age of 28 weeks should be delivered at a tertiary neonatal unit.

Ethics statement
The current work was developed in the context of the National Clinical Audit of “Very Low Birth Weight Infants in the Republic of Ireland”. This audit collects data on the care and outcomes of newborn infants, aiming to review the care provided and recommend improvements to the quality and safety of care for newborn infants and their families. Neonatologists and paediatricians collect anonymised and confidential data on the care of these infants. No personal identifiers are obtained. In line with the Irish “Healthcare Audit Criteria and Guidance”, this does not require formal ethical approval.

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