Disparities in mortality rates among US infants born late preterm or early term, 2003-2005

National Trends in Preterm Infant Mortality in the United States by Race and Socioeconomic Status, 1995-2020

Importance

Inequalities in preterm infant mortality exist between population subgroups within the United States.

Objective

To characterize trends in preterm infant mortality by maternal race and socioeconomic status to assess how inequalities in preterm mortality rates have changed over time.

Design, Setting, and Participants

This was a retrospective longitudinal descriptive study using the US National Center for Health Statistics birth infant/death data set for 12 256 303 preterm infant births over 26 years, between 1995 and 2020. Data were analyzed from December 2022 to March 2023.

Exposures

Maternal characteristics including race, smoking status, educational attainment, antenatal care, and insurance status were used as reported on an infant's US birth certificate.

Main Outcomes and Measures

Preterm infant mortality rate was calculated for each year from 1995 to 2020 for all subgroups, with a trend regression coefficient calculated to describe the rate of change in preterm mortality.

Results

The average US preterm infant mortality rate (IMR) decreased from 33.71 (95% CI, 33.71 to 34.04) per 1000 preterm births per year between 1995-1997, to 23.32 (95% CI, 23.05 to 23.58) between 2018-2020. Black non-Hispanic infants were more likely to die following preterm births than White non-Hispanic infants (IMR, 31.09; 95% CI, 30.44 to 31.74, vs 21.81; 95% CI, 21.43 to 22.18, in 2018-2020); however, once born, extremely prematurely Black and Hispanic infants had a narrow survival advantage (IMR rate ratio, 0.87; 95% CI, 0.84 to 0.91, in 2018-2020). The rate of decrease in preterm IMR was higher in Black infants (-0.015) than in White (-0.013) and Hispanic infants (-0.010); however, the relative risk of preterm IMR among Black infants compared with White infants remained the same between 1995-1997 vs 2018-2020 (relative risk, 1.40; 95% CI, 1.38 to 1.44, vs 1.43; 95% CI, 1.39 to 1.46). The rate of decrease in preterm IMR was higher in nonsmokers compared with smokers (-0.015 vs -0.010, respectively), in those with high levels of education compared with those with intermediate or low (-0.016 vs - 0.010 or -0.011, respectively), and in those who had received adequate antenatal care compared with those who did not (-0.014 vs -0.012 for intermediate and -0.013 for inadequate antenatal care). Over time, the relative risk of preterm mortality widened within each of these subgroups.

Conclusions and Relevance

This study found that between 1995 and 2020, US preterm infant mortality improved among all categories of prematurity. Inequalities in preterm infant mortality based on maternal race and ethnicity have remained constant while socioeconomic disparities have widened over time.

Child mortality of twins and singletons among late preterm and term birth: a study of national linked birth and under-five mortality data of Korea

Twins involve a higher risk of perinatal complications compared to singletons. We compared the risk of under five mortality between twins and singletons among late preterm and term births. The national birth data of South Korea pertaining to the years 2010-2014 linked with the mortality record of children aged under 5 years in 2010-2019 was analyzed. The final study population was 2,199,632 singletons and 62,351 twins. We conducted a survival analysis of under-five mortality with adjustment for neonatal and familial factors. Overall under-five mortality rates during the study period were 3.6 and 2.0 for twins and singletons, respectively. Although the unadjusted overall under-five mortality was higher in twins (hazard ratio [HR] = 1.80, 95% confidence interval [CI]: 1.57, 2.06, overall risk), twin birth was associated with comparable or lower risk (HR = 0.70, 95% CI: 0.58, 0.85, overall; 0.70, 95% CI: 0.56, 0.87, excluding neonatal mortality; 0.59, 95% CI: 0.40, 0.86, excluding infant mortality) after controlling for both neonatal and familial factors. Twins born at a gestational age of 34-35 weeks showed a generally lower risk of under-five mortality than their singleton counterparts, regardless of model specification.Conclusion: Among late preterm and term birth, under-5-year mortalities for twins were lower than singleton births when adjusted for neonatal and familial risk factors. This highlights the differential implication of gestational age at birth between twin and singleton in the child mortality.

Late preterm births: neonatal mortality and morbidity in twins vs. singletons

OBJECTIVE

To examine the outcomes of twins and singletons in the late preterm period.

MATERIALS AND METHODS

This is a retrospective cohort study of data obtained for 165,894 births in California who delivered between 34 + 0 and 36 + 6 weeks. The primary outcome was neonatal and infant mortality. The secondary outcomes included the following neonatal morbidities: respiratory distress syndrome (RDS), intraventricular hemorrhage (IVH), necrotizing enterocolitis (NEC), seizure, and sepsis. Univariate analysis was performed using chi-square test and multivariable logistic regression was used to adjust for potential confounders.

RESULTS

There were 143,891 singleton and 22,003 twin gestations included in the study. There was no difference in the primary outcome, neonatal and infant mortality between twins and singletons delivered at 34 and 36 weeks. After controlling for multiple potential confounders, significant differences in secondary outcomes of neonatal morbidity were identified. At 34 weeks, twins had significantly higher rates of IVH (aOR 2.47 (95%CI 1.08-5.64)), NEC (aOR 2.46 (95%CI 1.42-4.29)), RDS (aOR 1.60 (95%CI 1.45-1.77)), and sepsis (aOR 1.19 (95%CI 1.05-1.34)) compared to singletons. By 36 weeks, only an increased risk of RDS persisted among twins.

CONCLUSIONS

While there was no difference in mortality among twins and singletons in the late preterm period, twins may have significantly increased neonatal morbidity compared to singletons delivered between 34 + 0 and 36 + 6 weeks.

Racial and geographic variation in effects of maternal education and neighborhood-level measures of socioeconomic status on gestational age at birth: Findings from the ECHO cohorts

Preterm birth occurs at excessively high and disparate rates in the United States. In 2016, the National Institutes of Health (NIH) launched the Environmental influences on Child Health Outcomes (ECHO) program to investigate the influence of early life exposures on child health. Extant data from the ECHO cohorts provides the opportunity to examine racial and geographic variation in effects of individual- and neighborhood-level markers of socioeconomic status (SES) on gestational age at birth. The objective of this study was to examine the association between individual-level (maternal education) and neighborhood-level markers of SES and gestational age at birth, stratifying by maternal race/ethnicity, and whether any such associations are modified by US geographic region. Twenty-six ECHO cohorts representing 25,526 mother-infant pairs contributed to this disseminated meta-analysis that investigated the effect of maternal prenatal level of education (high school diploma, GED, or less; some college, associate's degree, vocational or technical training [reference category]; bachelor's degree, graduate school, or professional degree) and neighborhood-level markers of SES (census tract [CT] urbanicity, percentage of black population in CT, percentage of population below the federal poverty level in CT) on gestational age at birth (categorized as preterm, early term, full term [the reference category], late, and post term) according to maternal race/ethnicity and US region. Multinomial logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (CIs). Cohort-specific results were meta-analyzed using a random effects model. For women overall, a bachelor's degree or above, compared with some college, was associated with a significantly decreased odds of preterm birth (aOR 0.72; 95% CI: 0.61-0.86), whereas a high school education or less was associated with an increased odds of early term birth (aOR 1.10, 95% CI: 1.00-1.21). When stratifying by maternal race/ethnicity, there were no significant associations between maternal education and gestational age at birth among women of racial/ethnic groups other than non-Hispanic white. Among non-Hispanic white women, a bachelor's degree or above was likewise associated with a significantly decreased odds of preterm birth (aOR 0.74 (95% CI: 0.58, 0.94) as well as a decreased odds of early term birth (aOR 0.84 (95% CI: 0.74, 0.95). The association between maternal education and gestational age at birth varied according to US region, with higher levels of maternal education associated with a significantly decreased odds of preterm birth in the Midwest and South but not in the Northeast and West. Non-Hispanic white women residing in rural compared to urban CTs had an increased odds of preterm birth; the ability to detect associations between neighborhood-level measures of SES and gestational age for other race/ethnic groups was limited due to small sample sizes within select strata. Interventions that promote higher educational attainment among women of reproductive age could contribute to a reduction in preterm birth, particularly in the US South and Midwest. Further individual-level analyses engaging a diverse set of cohorts are needed to disentangle the complex interrelationships among maternal education, neighborhood-level factors, exposures across the life course, and gestational age at birth outcomes by maternal race/ethnicity and US geography.

[Effect of breastfeeding on the development of infection-related diseases during hospitalization in late preterm infants in 25 hospitals in Beijing, China]

OBJECTIVE

To investigate the incidence rate of infectious diseases during hospitalization in late preterm infants in Beijing, China, as well as the risk factors for infectious diseases and the effect of breastfeeding on the development of infectious diseases.

METHODS

Related data were collected from the late preterm infants who were hospitalized in the neonatal wards of 25 hospitals in Beijing, China, from October 23, 2015 to October 30, 2017. According to the feeding pattern, they were divided into a breastfeeding group and a formula feeding group. The two groups were compared in terms of general status and incidence rate of infectious diseases. A multivariate logistic regression analysis was used to investigate the risk factors for infectious diseases.

RESULTS

A total of 1 576 late preterm infants were enrolled, with 153 infants in the breastfeeding group and 1 423 in the formula feeding group. Of all infants, 484 (30.71%) experienced infectious diseases. The breastfeeding group had a significantly lower incidence rate of infectious diseases than the formula feeding group (22.88% vs 31.55%, P=0.033). The multivariate logistic regression analysis showed that breastfeeding was an independent protective factor against infectious diseases (OR=0.534, P=0.004), while male sex, premature rupture of membranes, gestational diabetes mellitus, and asphyxia were risk factors for infectious diseases (OR=1.328, 5.386, 1.535, and 2.353 respectively, P < 0.05).

CONCLUSIONS

Breastfeeding can significantly reduce the incidence of infectious diseases and is a protective factor against infectious diseases in late preterm infants. Breastfeeding should therefore be actively promoted for late preterm infants during hospitalization.

Ethnic and socioeconomic variation in cause-specific preterm infant mortality by gestational age at birth: national cohort study

OBJECTIVE

To describe ethnic and socioeconomic variation in cause-specific infant mortality of preterm babies by gestational age at birth.

DESIGN

National birth cohort study.

SETTING

England and Wales 2006-2012.

SUBJECTS

Singleton live births at 24-36 completed weeks' gestation (n=256 142).

OUTCOME MEASURES

Adjusted rate ratios for death in infancy by cause (three groups), within categories of gestational age at birth (24-27, 28-31, 32-36 weeks), by baby's ethnicity (nine groups) or area deprivation score (Index of Multiple Deprivation quintiles).

RESULTS

Among 24-27 week births (5% of subjects; 47% of those who died in infancy), all minority ethnic groups had lower risk of immaturity-related death than White British, the lowest rate ratios being 0.63 (95% CI 0.49 to 0.80) for Black Caribbean, 0.74 (0.64 to 0.85) for Black African and 0.75 (0.60 to 0.94) for Indian. Among 32-36 week births, all minority groups had higher risk of death from congenital anomalies than White British, the highest rate ratios being 4.50 (3.78 to 5.37) for Pakistani, 2.89 (2.10 to 3.97) for Bangladeshi and 2.06 (1.59 to 2.68) for Black African; risks of death from congenital anomalies and combined rarer causes (infection, intrapartum conditions, SIDS and unclassified) increased with deprivation, the rate ratios comparing the most with the least deprived quintile being, respectively, 1.54 (1.22 to 1.93) and 2.05 (1.55 to 2.72). There was no evidence of socioeconomic variation in deaths from immaturity-related conditions.

CONCLUSIONS

Gestation-specific preterm infant mortality shows contrasting ethnic patterns of death from immaturity-related conditions in extremely-preterm babies, and congenital anomalies in moderate/late-preterm babies. Socioeconomic variation derives from congenital anomalies and rarer causes in moderate/late-preterm babies. Future research should examine biological origins of extremely preterm birth.

A Program Model Describing a Community-Based Mother and Infant Health Program

BACKGROUND AND PURPOSE

The objective of this study was to formulate a MOMS Orange County program model to describe the components and function of a successful community-based maternal and infant health program.

METHODS

A logic framework was used to guide the development of the MOMS program model. Twenty-five MOMS staff members were interviewed; MOMS documents and existing research literature were reviewed. Content analyses were used to identify themes of interviews and the review guide was used to summarize the documents.

RESULTS

The key components of the MOMS program were identified to formulate a narrative and graphic model. The main elements of this model included: target population (underserved women who have low socioeconomic status and have limited access to healthcare in Orange County); theoretical assumptions (social determinants of health, human ecology, self-efficacy); goals (empower women, enhance health of infants, strengthen families); inputs (funded by public and private sources; 50 staff members); activities (care-coordination home visitation community-center group health education); outputs (the number of home visitations, referrals to medical and/or psychological services, and group health education classes); and outcomes (short-term: healthy pregnancy, birth outcomes, family support; medium-term: postpartum well-being, infant development, family functioning; long-term: women's well-being, children's development, family relationships. Future research should test how this model functions to empirically improve maternal, newborn, child, and family health.

IMPLICATIONS FOR PRACTICE

The MOMS program provides a new approach to community-based maternal and infant health interventions focusing on health promotion and disease prevention for underserved families in socioeconomically disadvantaged communities.

Early childhood health and morbidity, including respiratory function in late preterm and early term births

Late preterm (LP) and early term (ET) infants have generally been considered in the same way as their healthy full term (FT) counterparts. It is only in the last decade that an increased risk of later poor health in children born LP has been recognised; evidence for health outcomes following ET birth is still emerging. However, reports are largely consistent in highlighting an increased risk, which lessens approaching FT but is measurable and persists into adolescence and beyond. The most thoroughly explored area to date is respiratory morbidity. This article reviews the body of available evidence for effects of LP birth on pulmonary function and ongoing morbidity, and other areas where an increased risk of health problems has been identified in this population. Implications for delivery of health care are considered and areas for further research are highlighted.

Evaluation of an intervention supporting breastfeeding among late-preterm infants during in-hospital stay

BACKGROUND

Late-preterm infants show lower breastfeeding rates when compared with term infants. Current practice is to keep them in low-risk wards where clinical guidelines to support breastfeeding are well established for term infants but can be insufficient for late-preterm.

OBJECTIVE

The aim of this study was to evaluate an intervention supporting breastfeeding among late-preterm infants in a maternity service in the Basque Country, Spain.

METHODS

The intervention was designed to promote parents' education and involvement, provide a multidisciplinary approach and decision-making, and avoid separation of the mother-infant dyad. A quasi-experimental study was conducted with a control (n=212) and an intervention group (n=161). Data was collected from clinical records from November 2012 to January 2015. Feeding rate at discharge, breast-pump use, incidence of morbidities, infant weight loss and hospital stay length were compared between the two groups.

RESULTS

Infants in the control group were 50.7% exclusive breastfeeding, 37.8% breastfeeding, and, 11.5% formula feeding at discharge, whereas in the intervention group, frequencies were 68.4%, 25.9%, and 5.7%, respectively (p=0.002). Mothers in the intervention group were 2.66 times more likely to use the breast-pump after almost all or all feeds and 2.09 times more likely to exclusively breastfeed at discharge. There were no significant differences in morbidities and infant weight loss between groups. Hospital stay was longer for infants who required phototherapy in the intervention group (p=0.009).

CONCLUSION

The intervention resulted in a higher breastfeeding rate at discharge. Interventions aimed to provide specific support among late-pretem infants in maternity services are effective.

Gestational age and 1-year hospital admission or mortality: a nation-wide population-based study

Background

Describe the 1-year hospitalization and in-hospital mortality rates, in infants born after 31 weeks of gestational age (GA).

Methods

This nation-wide population-based study used the French medico-administrative database to assess the following outcomes in singleton live-born infants (32–43 weeks) without congenital anomalies (year 2011): neonatal hospitalization (day of life 1 – 28), post-neonatal hospitalization (day of life 29 – 365), and 1-year in-hospital mortality rates. Marginal models and negative binomial regressions were used.

Results

The study included 696,698 live-born babies. The neonatal hospitalization rate was 9.8%. Up to 40 weeks, the lower the GA, the higher the hospitalization rate and the greater the likelihood of requiring the highest level of neonatal care (both p < 0.001). The relative risk adjusted for sex and pregnancy-related diseases (aRR) reached 21.1 (95% confidence interval [CI]: 19.2-23.3) at 32 weeks. The post-neonatal hospitalization rate was 12.1%. The raw rates for post-neonatal hospitalization fell significantly from 32 – 40 and increased at 43 weeks and this persisted after adjustment (aRR = 3.6 [95% CI: 3.3–3.9] at 32 and 1.5 [95% CI: 1.1–1.9] at 43 compared to 40 weeks). The main causes of post-neonatal hospitalization were bronchiolitis (17.2%), gastroenteritis (10.4%) ENT diseases (5.4%) and accidents (6.2%). The in-hospital mortality rate was 0.85‰, with a significant decrease (p < 0.001) according to GA at birth (aRR = 3.8 [95% CI: 2.4–5.8] at 32 and 6.6 [95% CI: 2.1–20.9] at 43, compared to 40 weeks.

Conclusion

There’s a continuous change in outcome in hospitalized infants born above 31 weeks. Birth at 40 weeks gestation is associated with the lowest 1-year morbidity and mortality.

Safe Sleep Infant Care Practices Reported by Mothers of Twins

BACKGROUND

The high prevalence of prematurity and low birth-weight places twin infants at increased risk for sudden unexpected infant death (SUID) and/or sudden infant death syndrome (SIDS). Risk for these SUID and SIDS is affected by a combination of nonmodifiable intrinsic risk factors and modifiable extrinsic stressors including infant care practices related to sleep. Although adherence to the full scope of American Academy of Pediatrics (AAP) 2011 recommendations is intended to decrease risk, these recommendations are aimed at singleton infants and may require tailoring for families with multiple infants.

PURPOSE

The study describes infant care practices reported by mothers of twins in the first 6 months postpartum.

METHODS

Mothers caring for twin infants (N = 35) were surveyed online both longitudinally (at 2, 8, 16, and 24 weeks after infant hospital discharge) and cross-sectionally. AAP recommendations (2011) guided survey content.

RESULTS

The degree of adherence to AAP recommendations varied over time. For example, mothers of twins reported 100% adherence to placing twins supine for sleep initially, but many reported putting babies on their stomachs for naps as twins became older. Sharing a parent's bedroom decreased over time as did frequency of crib sharing. Fewer than half of mothers offered a pacifier most or all of the time for sleep.

IMPLICATIONS FOR PRACTICE

Opportunities exist for development of an educational program geared specifically for postpartum parents of twins.

IMPLICATIONS FOR RESEARCH

Barriers affecting adherence to AAP recommendations and effectiveness of educational programs addressing needs of this unique population need further exploration.

Time trends and risk factor associated with premature birth and infants deaths due to prematurity in Hubei Province, China from 2001 to 2012

Background

The nutrition and epidemiologic transition has been associated with an increasing incidence of preterm birth in developing countries, but data from large observational studies in China have been limited. Our study was to describe the trends and factors associated with the incidence of preterm birth and infant mortality due to prematurity in Hubei Province, China.

Methods

We conducted a population-based survey through the Maternal and Child Health Care Network in Hubei Province from January 2001 to December 2012. We used data from 16 monitoring sites to examine the trend and risk factors for premature birth as well as infant mortality associated with prematurity.

Results

A total of 818,481 live births were documented, including 76,923 preterm infants (94 preterm infants per 1,000 live births) and 2,248 deaths due to prematurity (2.75 preterm deaths per 1,000 live births). From 2001 to 2012, the incidence of preterm birth increased from 56.7 to 105.2 per 1,000 live births (P for trend < 0.05), while the infant mortality rate due to prematurity declined from 95.0 to 13.4 per 1,000 live births (P for trend < 0.05). Older maternal age, lower maternal education, use of assisted reproductive technology (ART), higher income, residence in urban areas, and infant male sex were independently associated with a higher incidence of preterm birth (all p values < 0.05). Shorter gestation, lower birth weight, and lower income were associated with a higher mortality rate, while use of newborn emergency transport services (NETS) was associated with a lower preterm mortality rate (all p values < 0.05).

Conclusion

An increasing incidence of preterm birth and a parallel reduction in infant mortality due to prematurity were observed in Hubei Province from 2001 to 2012. Our results provide important information for areas of improvements in reducing incidence and mortality of premature birth.

Electronic supplementary material

The online version of this article (doi:10.1186/s12884-015-0767-x) contains supplementary material, which is available to authorized users.

Role of stress in low birthweight disparities between black and white women: a population-based study

AIM

This study examines the role of stress in low birthweight (LBW) risk in Black and White women in the United States.

METHODS

Data from the 1998-2000 Fragile Family and Child Wellbeing Study were used (n = 3869). We included several self-reported conditions which we categorised as stressors (i.e. socio-economic conditions, health behaviours, access to quality care and cultural factors), then we used logistic regression models to analyse the role of stressors in explaining the health disparities in LBW.

RESULTS

Most women were unmarried (59% for White women and 87% for Black women). Among unmarried White women, the only stressor associated with a higher likelihood of LBW was smoking (odds ratio (OR) = 2.0, 95% confidence interval (CI) (1.2, 3.3)). Among unmarried Black women, smoking (OR = 1.7, 95% CI (1.2, 2.3)), drug use (OR = 1.7, 95% CI (1.0, 2.6)), paying for the baby's birth with government resources (OR = 1.6, 95% CI (1.1, 2.4)) and religious affiliation (OR = 1.6, 95% CI (1.0, 2.5)) were associated with higher likelihood of LBW. Among married White women, older age (OR = 1.1, 95% CI (1.0, 1.2)), smoking (OR = 5.2, 95% CI (1.7, 15.5)), using governmental resources to pay for birth (OR = 3.6, 95% CI (1.0, 12.4)) and living in governmental housing (OR = 9.1, 95% CI (2.0, 41.1)) were associated with higher likelihood of LBW. No stressors were statistically significant for married Black women.

CONCLUSION

We analysed a large number of stressors at the individual, household and societal levels and found differences on the stressors among Black and White women. However, the stressors included in the analyses did not fully explain the racial disparities in LBW.