Discussion

To our knowledge, this is the first nationally comprehensive study to identify racial, ethnic, and socio-economic disparities in neonatal ICU admission rates among a large cohort of neonates born with cyanotic CHD. Markers of low socio-economic status were independently associated with increased odds of neonatal ICU admission. Additionally, even after adjusting for pre-term birth, Black race was independently associated with increased odds of neonatal ICU admission, while Hispanic ethnicity was associated with decreased odds of neonatal ICU admission. Taken together, these findings suggest that race, ethnicity, and socio-economic status are important determinants of disparate birth outcomes among neonates born with cyanotic CHD.

Neonatal ICU admission rates in the study cohort increased significantly throughout the study period, echoing a similar trend in neonatal ICU admission rates in the general neonatal population. ^{Reference Kim, Ganduglia-Cazaban, Chan, Lee and Goodman12} This increase may be explained by the considerable growth in number and size of neonatal ICUs in recent years, as well as increased prenatal screening for CHD and improved prenatal detection rates over time. ^{Reference Boghossian, Geraci, Phibbs, Lorch, Edwards and Horbar13–16} However, neonatal ICU admission rates remained consistently high for non-Hispanic Black neonates as well as neonates with markers of low maternal socio-economic status and low maternal educational attainment. While neonatal ICU rates were overall higher in the neonatal CHD population than in the general neonatal population, our findings highlight persistent disparities in the likelihood of neonatal ICU admission even after accounting for known clinical neonatal ICU admission risk factors, including pre-term birth and low birthweight. This finding is consistent with previous literature that has found wide racial, ethnic, and socio-economic gaps in adverse birth outcomes. ^{Reference Dominguez17–Reference Blumenshine, Egerter, Barclay, Cubbin and Braveman20}

Neonates born to Hispanic mothers had decreased odds of neonatal ICU admission, despite high rates of WIC enrolment and later onset of prenatal care among Hispanic mothers. These results agree with prior work that has found that rates of adverse birth outcomes can be lower among Hispanic neonates than among non-Hispanic White and non-Hispanic Black neonates, despite prevalent social risk factors (e.g., low socio-economic status and low health literacy) among Hispanic mothers. ^{Reference de Jongh, Locke, Paul and Hoffman10,Reference Driscoll21} This “Hispanic Paradox” has been documented in the literature and may be explained by differential prenatal experiences and birth outcomes among Hispanic mothers born in the United States versus those born outside of the United States. ^{Reference McGlade, Saha and Dahlstrom22,Reference Hoggatt, Flores, Solorio, Wilhelm and Ritz23} A recent study identified considerable heterogeneity in adverse birth outcomes among Hispanic mothers after disaggregation by country of origin. ^{Reference Borrell, Bolumar, Rodriguez-Alvarez and Nieves24} Sociocultural factors that contribute to this phenomenon are maintained by local community networks that provide informal social supports and systems of prenatal care that often diminish with acculturation. ^{Reference McGlade, Saha and Dahlstrom22,Reference Hoggatt, Flores, Solorio, Wilhelm and Ritz23,Reference Zolitschka, Miani and Breckenkamp25} Decreased odds of neonatal ICU admission among Hispanic neonates in this study may reflect this paradox. Reduced risk of neonatal ICU admission among Hispanic neonates may also reflect reduced access to risk-appropriate neonatal care among Hispanic mothers, which may be influenced by the geographic distribution of the Hispanic population in the United States as well as variable access to neonatal ICUs along the rural–urban continuum. ^{Reference Lorch, Rogowski, Profit and Phibbs26}

While disparities in CHD outcomes across the lifespan are well documented, the causal mechanisms by which sociodemographic disparities in CHD outcomes arise remain poorly understood. ^{Reference Peyvandi, Baer and Moon-Grady3,Reference Lopez, Baker-Smith and Flores9,Reference Oster, Strickland and Mahle27} One factor that may drive disparities in CHD outcomes is prenatal care and corresponding prenatal CHD diagnosis, which has been shown to reduce the likelihood of perinatal and pre-operative morbidity and mortality in neonates with CHD. ^{Reference Krishnan, Jacobs and Morris8,Reference Holland, Myers and Woods28–Reference Tran, Tran and Lemus30} Consistent with this, our study found that delayed prenatal care was associated with significantly increased odds of neonatal ICU admission. This relationship is exacerbated among Black mothers and mothers of low socio-economic status due to increased barriers to accessing prenatal care that are affected by geographic proximity to care, implicit bias, structural racism, affordability, and community-level social acceptance, among other factors. ^{Reference Holcomb, Pengetnze, Steele, Karam, Spong and Nelson31–Reference Lopez, Morris and Krishnan34} It is possible that the disparities observed in this study are explained by sociodemographic differences in prenatal CHD diagnosis, which could not be identified in the data source underlying this study.

The increased odds of neonatal ICU admission among neonates born to mothers of Black race and low socio-economic status in our study may also indicate increased severity of disease in these neonates or other complicating risk factors. Several prior studies have found that Black infants tend to have more complex types of CHD. ^{Reference Mullen, Zhang, Lui, Romfh, Rhee and Wu35,Reference Knowles, Ridout and Crowe36} Moreover, previous work has found that CHD mortality remains the highest among non-Hispanic Black individuals and that a significant portion of inferior outcomes among Hispanic and non-Hispanic Black infants with CHD can be explained by varied exposure to adverse maternal-fetal environments. ^{Reference Lopez, Morris, Sexson Tejtel, Espaillat and Salemi2,Reference Santana, Peyvandi and Costello37} In the general neonatal population, non-Hispanic Black neonates have higher rates of neonatal ICU admissions than non-Hispanic White and Hispanic neonates, but these differences diminish after risk stratification. Racial and ethnic differences in neonatal ICU admission are pronounced in birthweight-stratified analyses, with the largest differences among neonates with normal to high birthweights. While this study did adjust for birthweight and pre-term birth in modelling neonatal ICU admission risk, CHD lesion type, clinical severity, and additional risk factors could not be measured. It is possible that these variables explain some portion of the sociodemographic disparities in neonatal ICU admissions observed in this study.

Increased rates of neonatal ICU admission among Black and low socio-economic status neonates are concerning for various reasons. First, there are well-documented racial, ethnic, and socio-economic inequities in the quality of neonatal intensive care received by neonates, with Black neonates consistently receiving neonatal care at lower-quality neonatal ICUs than White neonates. ^{Reference Lorch, Rogowski, Profit and Phibbs26,Reference Ravi, Iacob and Profit38,Reference Horbar, Edwards and Greenberg39} Among neonates with CHD, equitable access to high-quality neonatal care is crucial, as there are known survival advantages for neonates born in neonatal ICUs with high levels of care and high patient volumes. ^{Reference Phibbs, Baker, Caughey, Danielsen, Schmitt and Phibbs40} Furthermore, when complex CHD is diagnosed prenatally, perinatal care coordination at tertiary centres with dedicated paediatric cardiac surgical teams has been shown to improve perioperative outcomes in neonates with CHD. ^{Reference Chung, Lee and Kim41,Reference Mahle, Clancy, McGaurn, Goin and Clark42} Second, the CHD population is known to consume a disproportionate share of health resources, with neonatal ICU patients among the highest utilisers of hospital resources. ^{Reference Edelson, Rossano and Griffis43–Reference Johnson, Tani and Puchalski45} Neonatal ICU admissions in the CHD population may, therefore, pose significant financial burdens to families from historically marginalised and disadvantaged communities. Further work is needed to understand how differences in neonatal ICU admission rates correlate with differential resource use among neonates with CHD, with a particular focus on racially minoritised neonatal patients and patients of low socio-economic status. ^{Reference Edelson, Rossano and Griffis43,Reference Guilcher, Bronskill, Guan and Wodchis44}