Another look at the black-white gap in gestation-specific perinatal mortality.

In the US, black infants born near or at term experience higher mortality than white infants. To extend our understanding of black-white differences in the relative advantages of growth (measured by birthweight) for gestational age, we compared race-specific rates of perinatal mortality by deviation in grams from the median birthweight for four categories of gestation (35-36, 37-38, 39-41, and 42-43 weeks). We also used race-specific standards to examine the difference between the median birthweight and the optimum birthweight (i.e. birthweight with the lowest mortality). The data, which were derived from vital records for singletons delivered in the US from 1983-1984, comprised 24,626 fetal and neonatal deaths among 5,157,197 white infants and 5973 fetal and neonatal deaths among 926,678 black infants. At all deviations from the median birthweight, black infants had relatively better survival at 35-36 weeks of gestation. This advantage was reversed among infants with gestations of 39-41 and 42-43 weeks. The optimum birthweight for black infants with gestations greater than or equal to 37 weeks was closer to their median birthweight than was that for white infants. For black infants with gestations of 39-41 weeks, the optimum birthweight was 187g (95% confidence interval (CI): 150-234) greater than the median birthweight (3289g); for comparable white infants the optimum birthweight was 397g (95% CI: 366-431) greater than the median birthweight (3487g). To reduce the black-white gap in perinatal mortality, we need a better understanding of aetiological relations between gestation, growth, and mortality.     

Changing patterns of low birthweight and preterm birth in the United States, 1981-98

Low birthweight (LBW) and preterm birth are primary risk factors for infant morbidity and mortality in the US. With increasing multiple births and delayed childbearing, it is important to examine the separate contributions of these characteristics to the increases in LBW and preterm birth rates. US natality records from 1981, 1990 and 1998 were used to calculate LBW (% births <1500, 1500-2499, <2500 g) and preterm (% births <29, 29-32, 33-36, <37 weeks gestation) rates. Data were stratified by maternal race (black or white) and plurality (singleton vs. multiple birth). LBW and preterm rates among singletons were adjusted for maternal age to examine the influence of demographic shifts on LBW trends. From 1981 to 1998, LBW increased 12% among white infants, but remained relatively stable among black infants. During the same time, preterm birth increased 23% among white infants compared with 3% among black infants. For both black and white infants, the increase in LBW and preterm births was greater among multiple births than among singletons. Adjustment for maternal age did not reduce the temporal increase in LBW or preterm birth among singletons. Black infants continue to experience a markedly higher incidence of LBW and preterm birth, but the racial gap in these outcomes has narrowed slightly in recent years as a result of increasing LBW and preterm birth among white births. The differing trends for white and black infants are the consequence of a disparate trend in the incidence and outcome of multiple births coupled with increases in LBW and preterm birth among white singletons. Understanding the differential patterns in birth outcomes among white and black infants is necessary to develop effective interventions designed to decrease racial disparities in pregnancy outcome.     

Changes in the black-white infant mortality gap from 1983 to 1991 in the United States

Background: The long-standing difference in infant mortality in the United States between black and white infants has increased in recent years. To help identify the cause, we evaluated changes in birthweight distributions (BDs) and birthweight-specific mortality rates (BSMRs) among black and white infants born in the United States between 1983 and 1991.Methods: Using national linked birth and death certificate data, we limited analyses to singleton births that occurred in the United States to resident, non-Hispanic black and white women. Birthweight data were analyzed in 500 g increments. The black-white gap was partitioned into deaths due to differences in BDs and BSMRs.Results: The black-white infant mortality rate ratio increased from 2.1 in 1983 to 2.4 in 1991. Decreases in BSMRs among infants weighing from 500 to 2499 g occurred in both groups but were smaller among black than white infants; consequently, the percentage of excess deaths to black infants due to differences in BSMRs almost doubled during the study period, from 6.5% to 11.9%. Rates of very low birthweight (VLBW, <1,500 g) increased for black infants, but the BD for white infants changed little. Although about 90% of the excess deaths to black infants resulted from differences in BDs, the changes in BDs had a minimal effect on the widening infant mortality gap.Conclusions: A significant reduction in the black-white infant mortality gap will require a reduction in VLBW and low birthweight (LBW, <2,500 g). To keep the gap from growing, we must also investigate why decreases in BSMRs were smaller among black than white infants between 1983 and 1991.     

The Definition of Life: A Survey of Obstetricians and Neonatologists in New York City Hospitals Regarding Extremely Premature Births

Among obstetricians and neonatologists in administrative roles in New York City hospitals, a survey was initiated to compare the physicians’ definitions of live birth and fetal death, the gestational age at which they consider infants viable, and the resuscitation practices of the neonatologists. The target survey population was 34 neonatologists, and 39 obstetricians representing 41 of the City’s 43 maternity hospitals. A telephone survey was used to gather qualitative data from the physicians regarding their definitions of live birth, fetal death, and viability, and their practices regarding extremely premature births. Surveys were completed for 58 physicians, a response rate of 79% (94% for neonatologists and 67% for obstetricians). Physicians’ definitions of live birth and fetal death varied, with almost a third (29%) of physicians including gestational age as part of their live birth criteria. Most of the physicians (90%) consider infants born at ≥23 weeks gestation viable. Most neonatologists (97%) said they always resuscitate infants born at ≥23 weeks gestation, and most (94%) said they would never resuscitate infants born at <20 weeks gestation. For infants born at 20–22 weeks gestation, there were differences in resuscitation practices. There is a gap between clinical practices and reporting requirements for live birth and fetal death. Whereas reporting requirements are based on definitions of live birth and fetal death, physicians make resuscitation and other clinical decisions regarding extremely premature infants based on definitions of viability.     

The Prevalence of Socioeconomic and Behavioral Characteristics and their Impact on Very Low Birth Weight in Black and White Infants in Georgia

Objectives: We examined possible reasons for the disparity in the rate of very low birth weight (VLBW) delivery (<1500 g) in the United States between black women and white women. Methods: Using data from a population-based, case–control study of very low birth weight infants, we compared the prevalence of sociodemographic and behavioral characteristics between black and white mothers of normal birth weight infants; the difference in these characteristics between case and control mothers; and, using logistic regression, calculated odds ratios for VLBW for black versus white infants, adjusting for these characteristics. Results: Although black women were disadvantaged on every variable examined, they did not report more behavioral risk factors. Among white women, several traditional risk factors were associated with VLBW, while among black women, only marital status, cigarette smoking, and vitamin nonuse were associated with VLBW delivery. Controlling for the socioeconomic and behavioral factors reduced the odds ratio for VLBW delivery among black mothers from 3.7 to 3.3. Conclusions: Racial disparity in socioeconomic status may be greater than our current ability to adjust for it in epidemiologic studies. The fact that traditional risk factors were not associated with VLBW delivery in black women may be due to the very high prevalence of these risk factors among black women or to different or additional risks or stresses experienced by black women.     

Concordance among measures of pregnancy outcome based on fetal size and duration of gestation

Epidemiologic and clinical studies of pregnancy outcome often consider a variety of related, overlapping outcome measures. The overlap among these measures was analyzed using data from the Mount Sinai Hospital Perinatal Data Base, New York City, New York. A total of 52,621 births from 1986 through 1996 were included, with information on gender, ethnicity, birth weight, and gestational age assigned based on last menstrual period or early ultrasound. The authors considered very low birth weight (VLBW) (<1,500 g), low birth weight (LBW) (<2,500 g), degrees of preterm delivery (less than 32, 34, and 37 weeks' gestation), and small for gestational age (less than the 10th percentile of weight for gestational age) births. Infants at the extremes of gestational age (<32 or 34 weeks' gestation) were almost always LBW (97.6 and 91.7%, respectively), and those who were VLBW were almost always preterm (99.2%). However, only 69.2% of LBW infants were preterm, and 50.2% of preterm infants were LBW (kappa = 0.54). Only for VLBW and less than 32 weeks' gestation were both measures of overlap at least 70% (kappa = 0.98). The lack of concordance among measures suggests that multiple outcome measures be considered and that results from analyses using disparate measures not be compared directly.     

Neonatal intensive-care unit admission of infants with very low birth weight --- 19 States, 2006

Neonatal mortality is disproportionately common among infants with very low birth weight (VLBW) (<1,500 g [3.3 lbs]). In 2006, the mortality rate among infants with VLBW was 240.4 per 1,000 live births. Because neonatal intensive care has been shown to reduce mortality among infants with VLBW, current standards call for neonatal intensive-care for all infants with VLBW; however, the proportion of infants with VLBW who are admitted to a neonatal intensive care unit (NICU) is not known, nor are the predictors for NICU admission. To estimate the prevalence of admission to NICUs among infants with VLBW and assess factors predicting admission, CDC analyzed birth data from 2006 for 19 states. This report summarizes the results of that analysis, which found that overall, 77.3% of infants with VLBW were admitted to NICUs (range: 63.7% in California to 93.4% in North Dakota). Among infants with VLBW born to Hispanic mothers, 71.8% were admitted to NICUs, compared with 79.5% of those with non-Hispanic black mothers and 80.5% of those with non-Hispanic white mothers. Multivariate analysis of the data indicated that preterm delivery, multiple births, and cesarean delivery all were independently associated with greater prevalence of NICU admission among infants with VLBW. Wide variation was observed among states in the prevalence of NICU admission of infants with VLBW; these state data should be assessed further, and barriers to NICU admission should be identified and addressed.     

The intergenerational relationship between mother's birthweight, infant birthweight and infant mortality in black and white mothers

Summary. The relationship between the birthweight of white and black mothers and the outcomes of their infants were examined using the 1988 National Maternal and Infant Health Survey. White and black women who were low birthweight themselves were at increased risk of delivering very low birthweight (VLBW), moderately low birthweight (MLBW), extremely preterm and small size for gestational age (SGA) infants. Adjustment for the confounding effects of prepregnant weight and height reduced the risks of all these outcomes slightly, and more substantially reduced the maternal birthweight associated risk of moderately low birthweight among white mothers. There was little effect of maternal birthweight on infant birthweight-specific infant mortality in white mothers; however, black mothers who weighed less than 4 lbs at birth were at significantly increased risk of delivering a normal birthweight infant who subsequently died. Although the risks for the various outcomes associated with low maternal birthweight were not consistently higher in black mothers compared with white mothers, adjustment for prepregnant weight and height had a greater effect in white mothers than in black mothers. We suggest that interventions to reduce the risks for adverse pregnancy outcomes associated with low maternal birthweight should attempt to optimise prepregnant weight and foster child health and growth.     

Candidal versus bacterial late-onset sepsis in very low birthweight infants in Israel: a national survey

Candidal infections are one of the common causes of late-onset sepsis (LOS) among very low birthweight (VLBW) infants, and are associated with substantial morbidity and mortality. The aim of this study was to evaluate the perinatal and neonatal risk factors for fungal LOS compared with bacterial LOS in VLBW infants. This was a population-based observational study of VLBW infants in 28 neonatal intensive care units across Israel, with information on 11,830 infants born between 1995 and 2002 from the Israeli National VLBW infant database. The study population comprised 3054 infants with one or more episodes of LOS. Univariate analysis and logistic regression models were used to compare perinatal and neonatal risk factors between infants with fungal sepsis only (N=179) and those with bacterial sepsis only (N=2630). The mean birthweight and gestational age of infants with candidal LOS were significantly lower (940 g; 27.1 weeks) than those in the bacterial LOS group (1027 g; 28.3 weeks) (P<0.001). Logistic regression analysis showed that candidal sepsis, in contrast to bacterial sepsis, was independently associated with decreasing gestational age and bronchopulmonary dysplasia (BPD). In addition, BPD only [odds ratio (OR) 1.84; 95% confidence intervals (CI) 1.03-3.23] and BPD with postnatal steroid therapy (OR 2.66; 95% CI 1.59-4.46) were independently associated with an increased risk for candidal sepsis.     

Geographic Accessibility to Health Services and Neonatal Mortality Among Very-Low Birthweight Infants in South Carolina

Introduction Mortality for infants born with very-low birthweight (VLBW, 500–1499 grams) is markedly higher than for babies born with normal birthweight (2500–4000 grams). Although these high-risk infants show better outcomes in advanced care settings, only 80 % of VLBW infants born in South Carolina (SC) are delivered in hospitals with a level-III neonatal intensive care unit (NICU). The purpose of this research project was to assess geographic access to delivery hospitals and risk of neonatal death among singleton VLBW infants born in SC. Methods The linked birth and death records of a cross-sectional, population-based study of singleton VLBW infants born in SC between 2010 and 2012 were used (n = 2030). We assessed the impact of travel time from maternal residence to delivery hospital. Logistic regression modeling was performed with adjustments for maternal, newborn, and hospital characteristics. Results The neonatal mortality rate among singleton VLBW infants was 11.03 deaths per 100 live births in 2010–2012. We did not find a significant association between travel time to delivery hospital and neonatal mortality after adjusting for confounders. However, we found that a 1-week increase in gestational age (odds ratio (OR): 0.61) and non-Hispanic black mothers (versus non-Hispanic white mothers) (OR: 0.68) were associated with lower odds of neonatal death, whereas non-NICU admission at birth (OR: 5.90) was associated with increased odds of death. The results of the sensitivity analyses including both singleton and multiple births did not yield significant results for travel time and neonatal mortality in VLBW infants. Discussion Although we found no significant association between travel time and neonatal mortality in singleton VLBW births in SC, we identified significant factors consistent with those found in previous studies that may affect neonatal mortality.     

Very low birth weight: a problematic cohort for epidemiologic studies of very small or immature neonates

Despite widespread acceptance of the concept of very low birth weight (VLBW), i.e., birth weight of less than or equal to 1,500 g, VLBW infants represent an extremely heterogeneous group of newborns, including those with very immature gestational age and those who are more mature but extremely growth retarded. To demonstrate how use of the VLBW rubric can lead to confounding bias that is not only large in magnitude but impossible to control satisfactorily, the authors divided 640 consecutive live neonates born in the Royal Victoria Hospital, Montreal, Canada, from 1978 to 1987 into two overlapping groups: a VLBW cohort (birth weight, 500-1500 g; n = 573) and a gestational age cohort (gestational age, 23-30 completed weeks; n = 466). Variation in growth status by gestational age was much more uniform in the 23- to 30-week cohort. Thus, although mean birth weight was similar in the 500- to 1,500-g and 23- to 30-week cohorts (1,055 vs. 1,064 g), the 500- to 1,500-g cohort was more mature (mean gestational age, 28.8 vs. 27.8 weeks; upper range, 39.7 vs. 30.9 weeks) and had twice the rate of intrauterine growth retardation (25.7 vs. 11.5%). These differences in maturity and growth resulted in a misleading protective effect of intrauterine growth retardation against in-hospital death in the 500- to 1,500-g cohort (crude odds ratio = 0.55 (95% confidence interval 0.36-0.83] and a greater discrepancy in maturity between cesarean- and vaginally delivered infants (3.1 vs. 1.5 weeks) in the 500- to 1,500-g vs. 23- to 30-week cohorts. These differences arise from inextricable confounding of growth status and maturity in the 500- to 1,500-g cohort, the most mature infants also being the most growth retarded. The removal of well-grown infants with birth weights of greater than 1,500 g from the VLBW cohort leads to a progressively distorted spectrum of growth with advancing gestational age and an artifactual blunting of the beneficial effects of increasing maturity. The authors suggest that whenever fetal growth is an important exposure, outcome, or confounding variable, epidemiologic studies of extremely small or immature newborns should be based on gestational age rather than the VLBW criterion.     

US Black vs White disparities in foetal growth: physiological or pathological?

BACKGROUND: Birthweight for gestational age is lower in US Black infants than in US White infants. It is unknown, however, whether this difference is 'normal' (i.e. physiological) or reflects pathological foetal growth restriction. METHODS: We applied an analytic approach based on foetuses at risk to compare gestational age-specific rates of live birth, 'revealed' small-for-gestational-age (SGA), and neonatal mortality among singleton infants >or=22 weeks of gestation and >or=500 g born in 1998-2000 to US White (n = 9 012 194), US-born Black (n = 1 554 382), and foreign-born Black (n = 200 395) mothers. Graphical methods and Cox proportional hazards regression analyses were used to compare outcomes in the three ethnic groups. RESULTS: Rates of live birth and neonatal mortality were highest at all gestational ages in US-born Blacks, lowest in Whites, and intermediate in foreign-born Blacks. The revealed SGA pattern cohered much more closely with the observed pattern for neonatal mortality when SGA was defined based on a single, overall standard of birthweight for gestational age than when based on ethnic group-specific standards. CONCLUSION: The closer coherence of revealed SGA and neonatal mortality rates based on a single standard and the intermediate pattern among foreign-born Blacks strongly suggest that Black-White differences in birthweight for gestational age are pathological, rather than physiological.     

Disparities in Mortality Rates Among US Infants Born Late Preterm or Early Term, 2003–2005

The purpose of this study was to identify disparities in neonatal, post-neonatal, and overall infant mortality rates among infants born late preterm (34–36 weeks gestation) and early term (37–38 weeks gestation) by race/ethnicity, maternal age, and plurality. In analyses of 2003–2005 data from US period linked birth/infant death datasets, we compared infant mortality rates by race/ethnicity, maternal age, and plurality among infants born late preterm or early term and also determined the leading causes of death among these infants. Among infants born late preterm, infants born to American Indian/Alaskan Native, non-Hispanic black, or teenage mothers had the highest infant mortality rates per 1,000 live births (14.85, 9.90, and 11.88 respectively). Among infants born early term, corresponding mortality rates were 5.69, 4.49, and 4.82, respectively. Among infants born late preterm, singletons had a higher infant mortality rate than twins (8.59 vs. 5.62), whereas among infants born early term, the rate was higher among twins (3.67 vs. 3.15). Congenital malformations and sudden infant death syndrome were the leading causes of death among both late preterm and early term infants. Infant mortality rates among infants born late preterm or early term varied substantially by maternal race/ethnicity, maternal age, and plurality. Information about these disparities may help in the development of clinical practice and prevention strategies targeting infants at highest risk.     

State-Specific Trends in Preterm Delivery: Are Rates Really Declining Among Non-Hispanic African Americans Across the United States?

Objectives: This study sought to examine state-specific trends in preterm delivery rates among non-Hispanic African Americans and to assess whether these rates are influenced by misclassification of gestational age. Methods: The sample population consisted of singleton non-Hispanic White and non-Hispanic African–American infants born in 1991 and 2001 to U.S. resident mothers. For both time periods, state-specific and national preterm delivery rates were calculated for all infants, stratified by infant race/ethnicity. Next, birth-weight distributions within strata of gestational age were studied to explore possible misclassifications of gestational age. Lastly, state-specific and national preterm delivery rates among infants who weighed less than 2,500 g were separately computed. Results: National analyses showed that the frequency of preterm delivery increased by 15.8% among non-Hispanic Whites but declined by 10.3% among non-Hispanic African Americans over the same period. For both subgroups, a bimodal distribution of birth weights was apparent among preterm births at 28–31 weeks of gestation. The second peak with its cluster of normal-weight infants was more prominent among non-Hispanic African Americans in 1991 than in 2001. After excluding preterm infants who weighed 2,500 g or more, the national trends persisted. State-specific analyses showed that preterm delivery rates increased for both subgroups in 13 states during this period. Of these 13, 6 states had a number of non-Hispanic African–American births classified as preterm that were apparently term births mistakenly assigned short gestational ages. Such misclassification was more frequent in 1991 than in 2001 and inflated 1991 rates. Conclusion: There is heterogeneity in state-specific preterm delivery rates. Such differences are often overlooked when aggregate results are presented.     

The effect of mode of delivery on neonatal mortality in very low birthweight infants born in Victoria, Australia: Caesarean section is associated with increased survival in breech-presenting, but not vertex-presenting, infants

To determine whether the improved survival of very low birthweight (VLBW) infants (< 1500 g) born in Australia can be attributed to currently high rates of Caesarean section, we examined the associations between neonatal mortality and Caesarean section in singleton liveborn VLBW infants (500–1499 g) born during 1986–93 in Victoria, Australia, using data from the Victorian Perinatal Collection Unit. The infants included in this study had completed > 23 weeks of gestation, had no life-threatening malformations and had not been delivered by a repeat Caesarean without a trial of labour (n = 2763). For infants weighing 500–749 g, 750–999 g, 1000–1249 g and 1250–1499 g, the neonatal mortality rates were 56.1%, 25.7%, 13.0% and 4.3% respectively, and the Caesarean section rates were 33.1%, 42.3%, 54.8% and 55.8%. Nearly half of these births (n = 1269) were associated with one or more obstetric indications for Caesarean section (non-breech malpresentaion, fetal distress, prolapsed cord, placenta praevia, pre-eclampsia and hypertension). Overall, the odds ratio (OR) for neonatal death associated with Caesarean section was 0.92 [95% confidence interval 0.60–1.41], after adjustment for gestational age, birthweight, year of birth, type of hospital, presence or absence of labour, presentation and obstetric indications for Caesarean section. However, when the vertex-presenting (n = 1702) and breech-presenting (n = 746) infants were considered separately, the adjusted ORs for neonatal death were 1.98 [0.96–4.10] and 0.52 [0.29–0.96] respectively. For those infants without obstetric indications for Caesarean section, the adjusted ORs for neonatal death in vertex-presenting (n = 950) and breech-presenting (n = 446) infants were 3.80 [1.11–13.0] and 0.47 [0.23–0.6]. These recent population - based data support the view that Caesarean section does not enhance the neonatal survival of VLBW babies when obstetric complications are absent.     

Perinatal Disparities for Black Mothers and Their Newborns

Objectives In the United States, significant ethnic and racial health and healthcare disparities exist among our most vulnerable populations, new mothers and newborns. We sought to determine disparities in socioeconomic status, perinatal health, and perinatal healthcare for black mothers and their newborns cared for in well-baby nurseries compared with white mother/baby pairs in Pennsylvania. Methods A retrospective analysis of a merged data set containing birth and clinical discharge records was conducted. Perinatal data from 44,105 black mothers and their singleton newborns, >/=35 weeks gestational age cared for in Pennsylvania well-baby nurseries from 1998-2002 were compared with 88,210 white mother/baby pairs. Results Black mothers were younger and were much more likely to receive Medicaid or be uninsured compared with white mothers. They were less likely to be college-educated, married, or have prenatal care beginning in the first trimester. Infants born to black mothers were less likely to be delivered via Cesarean section, but were more likely to be born between 35 and 38 weeks gestation and be of low birth weight. Conclusions Numerous significant disparities exist for black mothers and their newborns cared for in well-baby nurseries in Pennsylvania. Since most newborns are cared for in this setting as opposed to intensive care environments, recognition of the differences that exist for this group when compared to well newborns of white mothers can help to improve healthcare and its delivery to this population. Federal and local initiatives must continue efforts to eliminate racial disparities.     

Intrauterine growth curves of weight,length, and head circumference for a predominantly Hispanic infant population.

The purpose of this study was to develop intrauterine growth curves in a predominantly Hispanic population of low socioeconomic status near sea level and to compare them with published intrauterine growth curves. Infants born at Los Angeles County-University of Southern California Medical Center provided the study population. Gestational age was determined by maternal history and confirmed by Ballard clinical assessment in 6,100 infants. Growth curves were developed for weight, length, and head circumference from 24 through 44 weeks gestation. The intrauterine curves were similar to those developed from white non-Hispanic births in California and from white middle class infants born in Portland, OR. The Los Angeles curves differed from other curves developed in Denver, CO, where the infants were significantly smaller from the 34th week of gestation. The authors found no adverse effects on intrauterine growth by race or socioeconomic status. The curves presented in this paper are more appropriate than the Denver curves for white populations born near sea level regardless of socioeconomic status.     

Apnea and its possible relationship to immunization in ex-premature infants

This study compared the characteristics of infants hospitalized with apnea that participated in a vaccine trial compared with two control groups which consisted of 100 infants randomly selected from the same vaccine trial and 52 consecutively born very low birth weight (VLBW) infants. A total of 23 infants were admitted with apnea of whom 19 weighed <1500 g at birth and all were born at <37 weeks gestation. More of the VLBW infants in the apnea group had neonatal neurological complications compared with the VLBW control group (p=0.005). Ten of 11 children with apnea within 72 h of immunization were possibly related to vaccination.     

Treatment differences between Aboriginal and white infants admitted to Canadian neonatal intensive care units

Previous studies reported differences in clinical treatments provided to ethnic minority children and white children. We examined whether there were differences in clinical treatments provided to Aboriginal and White infants in Canadian Neonatal Intensive Care Units (NICU) and whether these potential differences could be explained by differences in population characteristics, community size, maternal neighbourhood income and hospital treatment policies. The study population included 10 166 infants (n = 784 Aboriginal and n = 9382 white) admitted to 17 NICUs from all geographical regions of Canada participating in the Canadian Neonatal Network during January 1996-October 1997. We used logistic regression analyses to examine the association between ethnicity and each of seven clinical practices (surfactant treatment, antenatal steroids, blood transfusions, surgery, assisted ventilation, incubator use and transparental nutrition), after adjustment for potential confounders. We repeated theses analyses restricted to infants born <32 weeks gestation. In crude analyses, in the full sample, Aboriginal infants were less likely than white infants to receive surfactants, antenatal steroids, surgery, assisted ventilation, incubator and transparental nutrition. Among infants born <32 weeks gestation, Aboriginal infants were less likely than white infants to receive antenatal steroids, assisted ventilation, incubator and transparental nutrition. In both groups, adjusting for illness severity, gestational age and multiple births separately (model 2) and in combination with neighbourhood income and community size (model 3) resulted in non-significant associations between ethnicity and some of the treatments, but the addition of adjustment for the hospital variation in frequency of use of different treatments resulted in non-significant associations between ethnicity and all seven treatments. Additional studies are needed to explore the significance of hospital frequency of treatment and its relationship to ethnicity.