1. Introduction

Welcome to the ninth Very Low Birth Weight Infants in the Republic of Ireland Annual Report, produced by the National Perinatal Epidemiology Centre (NPEC). This report focuses on all babies born between 401 and 1500g and/or ≥22 weeks’ and <30 weeks' gestation in the Republic of Ireland for the calendar years 2023 and 2024  and compares outcomes to the preceding five years.

This report, which covers a two-year period, shows a slight increase in the number of VLBW infants born in Ireland (IE) in 2023, followed by the decrease that had been noticed in previous years. In total, 541 VLBW infants were born in 2023 and 490 born in 2024. Values from preceding years show a clear reduction from a peak of 662 VLBW infants born in 2015.  This reduction is largely explained by the reduction in the total number of livebirths reported over the same time period (from 65,536 in 2015 to 54,062 in 2024). ¹

Further information regarding methods, as well as guidance on interpreting rate ratios can be found in the Reference Materials section.

Figure 1. Map of neonatal centres and hospital groups in Ireland, 2024.

2. Overview

A total of 541 VLBW infants were reported to VON in Ireland in 2023 and a total of 490 were reported in 2024. Worldwide, a total of 60,537 (2023) and 58,673 (2024) VLBW infants were reported to the VON Network.

Overall, the number of VLBW infants recorded in Ireland for 2024 was just 1% lower than in 2020 (Table 1.1). The corresponding decrease in the number of livebirths in Ireland over the same time was of the order of 3% (from n=55,959 in 2020 to n=54,062 in 2024).¹

Figure 2 outlines the gestational age of VLBW infants reported in 2023 and 2024. As in previous years, the highest proportion of infants were born in the 27-29 weeks' gestation category (36%, n=197 of 541) in 2023 and (37%, n=182 of 490) in 2024. A total of 49 (9%) infants in 2023 and 35 (7%) in 2024 were born with a gestation below 24 weeks. In 2023, 47 (9%) of infants were born with a gestation of more than 32 weeks, similar to 2024 (n=44, 9%). In total,10% (52 of 541) and 7% (34 of 490) of VLBW infants born in 2023 and 2024, respectively, had a major congenital anomaly (MCA). 

Figure 2: Number of cases reported to VON in Ireland according to gestational age, 2020-2024.

Table 1.1: Number of cases reported to VON in 2020-2024 in Ireland, according to gestational age 

Figure 3 outlines the birthweights of VLBW infants born in 2023 and 2024. A total of 19 infants (4%) weighed ≤500g in 2023, of whom nine were ≤450g (the lowest birthweight recorded was 360g). The majority of infants in the same year (35% n=188) were born with a birthweight >1250g, 21 of whom had a birthweight >1500g.  

In 2024, a total of 23 (5%) of infants weighed ≤500g, of whom nine were ≤450g (the lowest birthweight recorded was 321g). Most infants, in 2024, were born with a birthweight >1250g (38%, n = 185), 19 of whom had a birthweight >1500g. 

Figure 3: Number of cases reported to VON in Ireland according to birth weight, 2020-2024.

Table 1.2: Number of cases reported to VON 2020-2024 in Ireland, according to birth weight. Birth weight unknown for one infant in 2024.

3. Infant Characteristics

Figure 4 outlines the characteristics of VLBW infants born in 2023 and 2024.

IE infants were similar to all VON infants with respect to infant sex and small for gestational age (SGA). 

The most notable statistically significant differences between IE infants and VON, related to provision of prenatal care, administration of antenatal steroids and antenatal magnesium sulphate, which, in both 2023 and 2024 had a higher prevalence in IE. Additionally, maternal hypertension, also showed a striking statistically significant lower incidence in Ireland than in the VON records for 2023 and 2024. In 2023 and 2024, maternal hypertension was reported in Ireland at 22.6% and 29.2% respectively, compared to 38.4% and 39.2% in all VON records (p-value = <0.001).

Table 2.1a: Infant characteristics in Ireland and VON, 2023 and Table 2.1b: Infant characteristics in IE and VON, 2024.

4. Survival

In 2023, 80% of the VLBW infants born in IE survived to discharge home or first birthday, which was lower than the 85% of all VON infants who survived (Table 3.1). In 2024, 84% of the VLBW infants born in IE survived to discharge home or first birthday, similar to the 84% of all VON infants who survived (Table 3.1). During the previous three years, the crude survival rate of 81% in IE (2020-2022) was lower than the survival rate of 84-86% among VON infants.  

In 2023, 50% of IE infants survived without the specified morbidities of severe IVH, chronic lung disease in infants born <33 weeks of gestation, NEC, pneumothorax, any late infection or cystic PVL.  This was slightly lower than the proportion of VON infants survived without these specified morbidities (54%) (Table 3.1).

In 2024, this percentage was 53% in IE, a similar proportion of VON infants survived without these specified morbidities (54%) (Table 3.1). 

Table 3.1: Survival of IE and VON infants, including those with congenital anomalies, 2020-2024. 

_{Note: Two infants in 2023 and two infants in 2024 with unknown survival outcomes are excluded from this table. * Defined as an infant who survives to discharge home or to first birthday. **Defined as survival without any of the following morbidities of severe IVH, chronic lung disease in infants <33 weeks' gestation, NEC, pneumothorax, any late infection or cystic PVL. P-values in bold indicate statistically significant difference (i.e. p<0.05).}

Survival to discharge of VLBW infants by gestational age and birthweight is reported in Figures 5 and 6 respectively for the years 2023 and 2024.

Survival to discharge increased with advancing gestational age until 30 weeks' gestation, above which there was a slight variation away from this pattern. This finding is consistent with previous years (Table 3.2, linked in footnote). Survival at 23 weeks' gestation was 23% (8 infants of a total of 35) for 2023 and 35% (6 infants of a total of 17) for 2024. 

Table 3.2: Survival to discharge by gestational age breakdown for IE infants, including those with congenital anomalies, 2020-2024.  Two infants in 2023 and two infants in 2024 with unknown survival outcomes are excluded from this figure.

Table 3.3: Survival to discharge by birth weight for IE infants, including those with congenital anomalies, 2020-2024. Two infants in 2023 and two infants in 2024 with unknown survival outcomes are excluded from this figure. An additional infant born in 2024 with an unknown birth weight is excluded from this figure.

5. Risk adjusted standardised mortality and morbidity ratios, key performance indicators

VON reports on several key performance indicators (KPIs). This allows Ireland to compare its outcomes to the Vermont Oxford Network. Such comparisons allow for the benchmarking of Ireland’s performance and the identification of areas for improvement.  

The KPIs are listed below, and relevant definitions are available in the Reference Materials section of the report:

1. Mortality 
2. Mortality Excluding Early Deaths  
3. Death or Morbidity  
4. CLD 
5. Pneumothorax 
6. Late Bacterial Infection 
7. Coagulase Negative Infection 
8. Nosocomial Infection 
9. Fungal Infection 
10. Any Late Infection  
11. Any IVH 
12. Severe IVH 
13. ROP 
14. Severe ROP 
15. Cystic PVL 
16. Necrotising Enterocolitis 

For each KPI, the number and percentage of IE infants that experienced the outcome in 2023 and 2024 is reported and illustrated in the following charts alongside the equivalent figures for all infants recorded in the VON database. The reporting of the KPIs in numbers and percentages for IE and VON infants are provided for descriptive purposes. Observed differences in KPIs may be related to the medical care provided but may also be due to differences between the IE and VON infant populations. Robust comparison of KPIs between IE and VON requires that pertinent differences between the infant populations are considered. This is done through the calculation of standardised mortality/morbidity Ratios (SMRs). More information regarding SMRs can be found in the Reference Materials section.

6. SMRs for key performance indicators, 2023-2024

For each key performance indicator, Tables 4.1a and 4.1b display the SMR, its 95% confidence interval, the difference between the observed and expected number of cases and the 95% confidence interval for this difference. 

In both years, the observed mortality risk among IE infants was significantly higher than the expected risk; 38% higher in 2023, and 29% higher in 2024. This finding was also evident when considering mortality excluding early death in 2023. In contrast, there was no statistically significant difference between IE and VON infants regarding the composite outcome of death or serious morbidity and for chronic lung disease. 

There was a significant excess risk of pneumothorax in 2023 (78% higher than expected), but the difference was not statistically significant in 2024. The risk of Intraventricular Haemorrhage (IVH) was significantly higher in both 2023 and 2024 (31% and 40% respectively). The risk of Severe IVH was also significantly greater in 2023 (45%), but not in 2024.

Table 4.1a: Risk-adjusted standardised mortality/morbidity ratios for key performance indicators in Ireland, 2023.

_{Note: “O” refers to the number of observed cases with the outcome and “E” to the expected number with the outcome of IE infants with birth weights 501-1500g. 95% confidence intervals (CIs) are provided for the SMR and the difference in observed and expected cases. *Indicates a statistically significant difference.}

Table 4.1b: Risk-adjusted standardised mortality/morbidity ratios for key performance indicators in Ireland, 2024.

_{Note: “O” refers to the number of observed cases with the outcome and “E” to the expected number with the outcome of IE infants with birth weights 501-1500g. 95% confidence intervals (CIs) are provided for the SMR and the difference in observed and expected cases. *Indicates a statistically significant difference.}

7. Key performance indicators and gestational age

Table 4.2 outlines the rates for each KPI according to gestational age (for all infants born≥ 23 weeks of gestations). Details on KPIs for infants born at 23 weeks are included however, conclusions cannot be drawn considering the small numbers recorded. 

Table 4.2: Risk for each key performance indicator according to gestational age categories of VLBW infants born in Ireland, 2023-2024.

_{Table 4.3. Risk for each key performance indicator according to gestational age categories of VLBW infants born in Ireland, 2020-2024. Table includes infants born at ≥ 23 weeks' gestation.}

8. Time trends in relative risk

For each KPI, Table 4.4 provides the annual SMRs for the five most recent years reported, 2020 to 2024 for infants with birth weights 501-1500g. In 2020, there were fewer cases of retinopathy of prematurity than expected, which was statistically significant. However, the KPIs for 2021 and 2022 showed several differences. For 2021 and 2022, there was a statistically significant excess in mortality, mortality excluding early deaths, pneumothorax, and IVH. In 2022, there was also an excess number of late bacterial, coagulase negative staphylococcus infections and nosocomial infections.

As mentioned above, for both 2023 and 2024, there was a statistically significant excess in mortality and IVH. In 2023, there was also a statistically significant excess in mortality excluding early death, pneumothorax, and Severe IVH. While an excess mortality risk is still reported, the 2024 SMR for mortality is the lowest reported since 2020, where the SMR was 1.10 (95% CI: 0.83, 1.37).

Cases of retinopathy of prematurity were in line with the expected number of cases in 2023 and 2024. While the risk of ROP was previously significantly less than VON, the difference has not been statistically significant since 2020.

Table 4.4: Standardised mortality/morbidity ratios for each key performance indicator, 2020-2024.

_{Note: SMR Standardised mortality/morbidity ratio. *Indicates a statistically significant difference.}

The SMRs for mortality in 2023 and 2024 show a slight decrease from 2022, where the highest standardised mortality ratios reported in any year since national reporting began in 2014 were observed (SMR = 1.46; 95% CI: 1.20-1.73). However, both 2023 and 2024 still had a statistically significant excess in mortality compared to VON infants. Below, we report findings from some initial analysis of mortality risk in 2023-2024.

Table 4.5: Risk adjusted standardised mortality ratios, 2023-2024.

_{Note: N is the total number of infants. O and E refer to the observed and expected number of deaths. Data relate to infants with birth weights 501-1500g. 95% confidence intervals (CIs) are provided for the SMR and the difference in observed and expected cases. *Indicates a statistically significant difference.}

Considering both years together, there were 943 VLBW infants born with a birth weight of 501-1500g, whom mortality probability was able to be calculated for. Of these 943 infants, 151, or approximately one in six, died. The observed risk of 16% was 1.34 times the expected risk of 11.9%; and the excess of 39 deaths was statistically significant.

The higher-than-expected risk of death was observed both in overall mortality and in late deaths (deaths occurring after 12 hours of life). The respective SMRs were virtually identical across all three categories, but for early deaths (deaths occurring in the delivery room or within the first 12 hours of life) it was not quite statistically significant.

In Figure 7 we examined the observed and expected mortality risk by gestational age at birth for the 927 VLBW infants born at 23 weeks of gestation or later with a birth weight of 501-1500g.

As anticipated, the observed and expected risks of death were highest for the most premature infants. In terms of the relative risk of death, there was a pattern noted whereby the elevated risk of death was most apparent for infants born at 23-27 weeks of gestation (SMR = 1.4; 95% CI = 1.17-1.63). Across each week of gestational age, the SMR ranged from 1.13-1.58; and the SMR for infants born at 23 weeks was statistically significant.

The overall SMR for infants born at 28+ week’s gestation was not statistically significant (SMR = 1.17; 95% CI = 0.81-1.54). The SMRs for individual weeks gestation for infants born at 28 weeks or later varied from 0.78 to 1.47, and none were statistically significant.

Figure 7: Risk-adjusted standardised mortality ratio (SMR) by gestational age, 2023-2024.

Note: Data relates to infants with birth weights 501-1500g. 95% confidence intervals (CIs) are provided for the SMR. Table 4.6: Risk-adjusted standardised mortality ratio by gestational age, 2023-2024.

Among the infants born at 23-27 weeks of gestation, their elevated risk of early death (deaths in the delivery room or during the first 12 hours of life) was not statistically significant, with an SMR of 1.22 (96% CI: 0.78-1.66). However, the excess mortality risk excluding early death was statistically significant, with a SMR of 1.48 (95% CI: 1.21-1.75).

Of the 331infants born at 23-27 weeks' gestation, 275 were born in tertiary centres, and 56 were born in non-tertiary centres. Of the 331 infants born in a tertiary centre at 23-27 weeks’ gestation, 30.2% (Table 4.7). This observed risk was 1.37 times higher than the expected risk of 22.1%, a statistically significant difference. The SMR was also statistically significant, but somewhat higher at 1.63, for the 56 infants born in a non-tertiary centre, as 33.9% of them died compared to an expected risk of 20.9%.

Table 4.7: Risk-adjusted standardised mortality ratio by timing of death and by type of birth hospital for infants born at 23-27 weeks of gestation, 2023 – 2024.

_{Note: N is the total number of infants. O and E refer to the observed and expected number of deaths. Data relate to infants with birth weights 501-1500g. 95% confidence intervals (CIs) are provided for the SMR and the difference in observed and expected cases. *Indicates a statistically significant difference. ˆThis table excludes two infants born between 23-27 weeks' gestation with unknown survival outcomes. One infant with an unknown birth hospital in 2023, and one infant born outside of the IE maternity services in 2024 are excluded from this table.}

9. Survival according to gestational age category and location of birth

There are 19 neonatal centres in Ireland that are affiliated with an Obstetric Service. These are classified as tertiary, regional or peripheral neonatal centres based on the number of births per annum in the affiliated obstetric centre and the level of neonatal consultant cover in the neonatal centre. There are four designated tertiary neonatal centres, four designated regional neonatal centres and eleven designated peripheral neonatal centres (Figure 1).  Each of the tertiary centres deliver more than 6,000 infants per annum and all provide 24-hour consultant neonatology cover. The regional centres have dedicated neonatal intensive care units (NICUs) but deliver less than 6,000 infants yearly and/or do not have 24-hour consultant neonatology cover. In 2024, one of these four centres delivered 3,000-4,000 infants, two centres delivered 2,000-3,000 infants and the fourth centre delivered fewer than 2,000 infants (Figure 1). Peripheral centres do not have dedicated NICUs, nor do they have dedicated consultant neonatology cover. They do have designated areas that care for newborn infants (i.e. Special Care Baby Units (SCBUs)), and these infants are under the care of general paediatricians. In 2023 and 2024, all peripheral centres delivered fewer than 2,000 infants. 

Of the 541 VLBW infants born in 2023, we had complete data both on location of birth (i.e. tertiary, regional, peripheral) and survival for 538 of these infants. For the 490 VLBW infants born in 2024, we had complete data both on location of birth (i.e. tertiary, regional, peripheral) and survival for 487 of these infants.

In 2023 and 2024, 775 infants (76%) were born in one of the four tertiary neonatal centres, 175 (17%) were born in one of the four regional neonatal centres and the remaining 75 infants (7%) were born in one of eleven peripheral centres (Table 5.1).  

This compares to 79% (n=388), 15% (n=72) and 7% (n=32) born in tertiary, regional and peripheral centres in 2022.⁶

Resuscitation in the delivery room is defined as the need for administration of positive pressure breaths either via a face mask and/or an endotracheal tube. Of the 702 infants who received resuscitation in the DR in 2023 and 2024 and whom survival information was available), 692 (99%) survived to admission to a NICU/SCBU but 10 infants died in the DR. Of these 692 admitted, 572 (82%) survived to discharge and 130 infants died (data not shown in table). 

Table 5.1: Survival of infants by category of neonatal centre, 2023-2024.

_{Note: One infant with an unknown birth hospital in 2023, and one infant born outside of the IE maternity services in 2024 are excluded from this table. Additionally, two infants in 2023 and two infants in 2024 with unknown survival outcomes are excluded from this table.}

Table 5.2 reports on the number of infants of each gestational age category who were born in tertiary, regional or peripheral centres and the number of these infants that were offered resuscitation at birth.

The 2018 report on mortality risk among VLBW infants between 2014-2016, recommended that all infants born at 23 weeks' gestation, presenting in a favourable condition, should be offered resuscitation.⁴ In 2023 and 2024, 96% of infants born at 23 weeks' gestation (n=49 of 51) were resuscitated at birth, whereas in 2022, 78% of the infants born at this gestational age received resuscitation. 

Table 5.2: Number of IE infants born in each category of neonatal centre who were administered resuscitation according to gestational age, 2023-2024.

_{Note: One infant with an unknown birth hospital in 2023, and one infant born outside of the IE maternity services in 2024 are excluded from this table.}

Despite the guidance from the Model of Care for Neonatal Services, published in 2015, that infants born <28 weeks should ideally be delivered in a tertiary neonatal centre, only 83% (n=299) of infants born between 23 and 27 weeks' gestation (n=359) in 2023 and 2024 were delivered in a tertiary neonatal centre.³  This figure has remained mostly unchanged since 2016, ranging from of 80-85%. ^6,7

A total of 45 (12%) infants delivered at <28 weeks were born in a regional neonatal centre and 27 (7%) were born in a peripheral centre in 2023 and 2024. 

Table 5.3 outlines the trend in survival of IE infants born at ≤22 weeks' gestation for the past 5 years. This is the first time survival at 22 weeks’ gestation has been reported since the beginning of this annual report in 2014. One infant born in 2023 at 22 weeks’ gestation and two infants born in 2024 at 22 weeks’ gestation survived.

Table 5.3: Survival of infants born at ≤22 weeks' gestation, 2020-2024.

Table 5.4 outlines the survival of infants born at 23 weeks' gestation in 2023 and 2024. The majority of these were born in tertiary centres (n=47, 92%), three (6%) were born in regional centres and one (2%) was born in a peripheral centre. In total, 49 of these infants (96%) were resuscitated in the delivery room, and 48 who were resuscitated survived to admission to the NICU. There were two DR deaths of which one had an MCA.  

Of note, of the four infants at this gestational age who were born in a regional or peripheral neonatal centre in 2023 and 2024, all four infants survived to admission to a NICU/SCBU. These infants were subsequently transferred within 48 hours of birth to a tertiary neonatal centre. Of the 49 VLBW infants born at 23 weeks' gestation who were admitted to NICU in 2023 and 2024, 14 of these infants survived to discharge.

Table 5.4: Survival of IE Infants born at 23 weeks' gestation by location of birth, 2023-2024.

_{Note: One infant with an unknown birth hospital in 2023 is excluded from this table.}

Table 5.5 outlines the trend in survival of IE infants born at 23 weeks' gestation for the past 5 years. There was an increase in the number of infants offered resuscitation in the DR from 70% in 2020 to 94% in 2023 and 100% in 2024. Survival to discharge home was 23% in 2023, and 35% in 2024. The lowest survival rate for these infants was recorded in 2014, the first year of this audit, with a value of 19%. 

Table 5.5: Survival of infants born at 23 weeks' gestation, 2020-2024.

10. Mortality and delivery room (DR) deaths

In 2023 and 2024, 18% (n=186) of VLBW babies born in Ireland died (VON 16%). The timing of these deaths is outlined in Figure 8. In 2023, a higher proportion of IE infants died in the DR, when compared to VON (p=0.002); this was also observed in 2024, but the difference was not statistically significant (p= 0.309). Tables detailing the mortality for 2023 and 2024 separately are linked in the footnote of Figure 8.

Table 6.1a: Mortality amongst IE and VON infants, 2023 and Table 6.1b: Mortality amongst IE and VON infants, 2024. Two infants in 2023 and two infants in 2024 with unknown survival outcomes are excluded from this figure.

As highlighted in Figure 9, the overall risk of death amongst VLBW infants in Ireland was 16-18% during 2014-2020, then it increased to 19-20% in 2021-2023 and was 16% again in 2024. The higher crude risk observed in 2021-2023 was associated with a higher risk of mortality excluding early death, which was 13-14% during this period compared to 7-11% in other years. Risk of death in the DR was 6-8% during 2014-2019 and was 5-6% since then.

Table 6.2: Distribution of deaths by timing amongst VLBW infants in Ireland, 2014-2024.

11. Deaths in the delivery room

In 2023, 6% (n=34) of IE infants died in the DR (VON =4%). In 2024, 5% (n=25) of IE infants died in the DR (VON=4%).

Of the 59 infants who died in the delivery room in 2023 and 2024, 25 (42%) had a Magor Congenital Anomaly (MCA). Of these 59 infants, a further 25 (42% of total DR deaths) were in infants without an MCA born at less than 24 weeks' gestation (24 infants born at ≤22 weeks and 1 infant born at 23 weeks). These factors may have impacted on the slightly higher delivery room death rate recorded in the IE population when comparing to VON. 

As seen in Table 6.3, of the 14 infants who died in the DR with a gestational age of >=28 weeks in 2023 and 2024, 93% had an MCA (n=13 of 14).

Table 6.3: Deaths in the delivery room, by gestational age category and presence of major congenital anomaly (MCA), 2023-2024.

Deaths in the DR by gestational age category, for both IE and VON infants, are detailed in Figure 10. There was a greater percentage of DR deaths in infants <22 weeks' gestation in Ireland compared to VON (100% vs 94% respectively), as well as at 22 weeks' gestation (72% vs 32% respectively).

Figure 10: Deaths in the delivery room, by gestational age category, IE and VON, 2023-2024

Table 6.4a: Deaths in the delivery room, by gestational age category in IE and VON, 2023 and Table 6.4b: Deaths in the delivery room, by gestational age category in IE and VON, 2024.

References

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