Does smoking during pregnancy mediate educational disparities in preterm delivery? Findings from three large birth cohorts

Mediating role of gestational weight gain in the relationship between socioeconomic status and preterm birth: a Chinese population-based study

BACKGROUND

The modifiable mechanisms underlying the association between socioeconomic status (SES) and preterm birth remain unclear. This study aimed to investigate the relationship between preterm birth and maternal SES or gestational weight gain (GWG), as well as the role of GWG in mediating SES disparities in preterm birth.

METHODS

Data was from a hospital-based sub-study of physical growth and development survey for Chinese newborns with various gestational ages. Singleton newborns aged from 24 to 42weeks' gestation and their mothers were included. Using information from maternal questionnaire, a composite SES was constructed with parental education and family annual income. GWG as mediator was calculated by deducting pre-pregnancy weight from maternal weight at delivery. Logistic regression model was adopted to investigate the association of preterm birth with SES or GWG. Causal mediation analysis was performed to measure mediating effect of GWG on the pathway from SES to preterm birth.

RESULTS

After controlling for potential confounders, risk of preterm birth was reduced by 12.4% (OR = 0.876, 95%CI:0.855-0.879) for per one-kilogram increase of GWG, and risk of preterm birth was reduced by 24% (OR = 0.760, 95%CI: 0.717-0.806) for per one-unit increase of SES score. Mediation analysis supported a significant association between higher SES and decreased risk of preterm partly through higher GWG, in which estimated proportion mediated by GWG was 13.04% (95%CI: 11.89-16.25). GWG also played a significant role as a mediator when socioeconomic status was indicated by maternal education, paternal education or family income. GWG mediated approximately 11.03% (95% CI: 8.56-18.25) of the total effect of SES on very preterm birth, which was greater than that for moderate preterm birth (6.72%, 95%CI: 2.72-31.52) and late preterm birth (9.04%, 95%CI: 5.24-24.04). A series of sensitive analysis confirmed the robustness of association of interest.

CONCLUSION

Increased GWG and higher socioeconomic status are strongly associated with a lower risk of preterm birth. GWG mediates socioeconomic disparities in preterm birth, most notably in very preterm birth. Understanding this mechanism will aid in the development of interventions and policy for maternal and child health care.

How are socioeconomic inequalities in preterm birth explained by maternal smoking and maternal body mass index: A mediation analysis

BACKGROUND

Preterm birth affects between 7% and 8% of births in the UK and is a leading cause of infant mortality and childhood disability. Prevalence of preterm birth has been shown to have significant and consistent socioeconomic inequalities.

OBJECTIVE

To estimate how much of the association between socioeconomic status (SES) and gestational age at birth is mediated by maternal smoking status and maternal body mass index (BMI).

METHODS

Retrospective cohort study of a maternity hospital in the UK. The analysis included all singleton live births between April 2009 and March 2020 to mothers 18 years old and over, between 22 weeks and 43 weeks gestation. We estimate two measures of mediation for four low gestational age categories: (i) The proportion eliminated the percentage of the effect of SES on low gestational age at birth that would be eliminated by removing the mediators, through the Controlled Direct Effects estimated using serial log-binomial regressions; and (ii) The proportion mediated is the percentage of the effect removed by equalising the distribution of the mediators across socioeconomic groups, estimated using Interventional Disparity Measures calculated through Monte Carlo simulations.

RESULTS

Overall, 81,219 births were included, with 63.7% low SES. The risk of extremely (0.3% of all births), very (0.7%) and moderately preterm birth (6.3%) was 1.71 (95% Confidence Interval [CI] 1.29, 2.31), 1.43 (95% CI 1.18, 1.73) and 1.26 (95% CI 1.19, 1.34) times higher in the low SES, compared to higher SES respectively. The proportion of this inequality eliminated by removing both maternal smoking and BMI was 43.4% for moderately preterm births. The proportion mediated for smoking was 33.9%, 43.0% and 48.4% respectively.

CONCLUSIONS

Smoking during pregnancy is a key mediator of inequalities in preterm birth, representing an area for local action to reduce social inequalities in preterm birth.

Prevalence of preterm birth in Scandinavian countries: a systematic review and meta-analysis

OBJECTIVES

As welfare societies, Scandinavian countries share characteristics of equality related to healthcare access, gender, and social services. However, cultural and lifestyle variations create country-specific health differences. This meta-analysis assessed the prevalence of preterm birth (PTB) and its categories in Scandinavian countries.

METHODS

A systematic search in key databases of literature published between 1990 and 2021 identified studies of the prevalence of PTB and its categories. Following the use of the Freeman-Tukey double arcsine transformation, a meta-analysis of weighted data was performed using the random-effects model and meta-prop method.

RESULTS

We identified 109 observational studies that involved 86,420,188 live births. The overall pooled prevalence (PP) of PTB was 5.3% (PP = 5.3%, 95% confidence interval [CI] 5.1%, 5.5%). The highest prevalence was in Norway (PP = 6.2%, 95% CI 5.3%, 7.0%), followed by Sweden (PP = 5.3%, 95% CI 5.1%, 5.4%), Denmark (PP = 5.2%, 95% CI 4.9%, 5.3%), and Iceland (PP = 5.0%, 95% CI 4.4%, 5.7%). Finland had the lowest PTB rate (PP = 4.9%, 95% CI 4.7%, 5.1%).

CONCLUSIONS

The overall PP of PTB was 5.3%, with small variations among countries (4.9%-6.2%). The highest and lowest PPs of PTB were in Norway and Finland, respectively.

Childhood Socioeconomic Characteristics and Risk of Inflammatory Bowel Disease: A Scandinavian Birth Cohort Study

BACKGROUND

Ecological observations suggest a negative relationship between childhood socioeconomic status (SES) and inflammatory bowel disease (IBD) risk. Individual-level analyses have been inconsistent and mostly lacked refined assessments of SES. We aimed to comprehensively study the association between early-life SES and later IBD.

METHODS

This study included 117 493 participants from the Norwegian Mother, Father and Child cohort and Swedish All Babies in Southeast Sweden cohorts. Participants were followed from birth (1997-2009) through 2021. IBD was identified through national patient registers. Questionnaire and register data were used to define parental educational level, employment, and household income level. Cox regression estimated adjusted hazard ratios (aHRs), accounting for other SES exposures and covariates (eg, parental IBD). Cohort-specific estimates were pooled using a random-effects model.

RESULTS

During 2 024 299 person-years of follow-up, 451 participants were diagnosed with IBD (All Babies in Southeast Sweden cohort, n = 113 and Norwegian Mother, Father and Child cohort, n = 338). Early-life maternal, but not paternal, educational level was associated with later IBD (low vs high educational level; pooled aHR, 1.81; 95% confidence interval [CI], 1.16-2.82; and pooled aHR, 1.20; 95% CI, 0.80-1.80; respectively). Having a nonworking mother or father was not significantly associated with IBD (pooled aHR, 0.69; 95% CI, 0.47-1.02; pooled aHR, 0.79; 95% CI, 0.45-1.37). High vs low household income level yielded a pooled aHR of 1.33 (95% CI, 0.94-1.89). Overall, results were largely consistent across cohorts.

CONCLUSIONS

In this prospective Scandinavian cohort study, low maternal educational level was, independent of other SES and covariates, significantly associated with later IBD in her child. Further research is needed to elucidate factors that may mediate this relationship.

Deficits in neural encoding of speech in preterm infants

Preterm children show developmental cognitive and language deficits that can be subtle and sometimes undetectable until later in life. Studies of brain development in children who are born preterm have largely focused on vascular and gross anatomical characteristics rather than pathophysiological processes that may contribute to these developmental deficits. Neural encoding of speech as reflected in EEG recordings is predictive of future language development and could provide insights into those pathophysiological processes. We recorded EEG from 45 preterm (≤ 34 weeks of gestation) and 45 term (≥ 38 weeks) Chinese-learning infants 0-12 months of (corrected) age during natural sleep. Each child listened to three speech stimuli that differed in lexically meaningful pitch (2 native and 1 non-native speech categories). EEG measures associated with synchronization and gross power of the frequency following response (FFR) were examined. ANCOVAs revealed no main effect of stimulus nativeness but main effects of age, consistent with earlier studies. A main effect of prematurity also emerged, with synchronization measures showing stronger group differences than power. By detailing differences in FFR measures related to synchronization and power, this study brings us closer to identifying the pathophysiological pathway to often subtle language problems experienced by preterm children.

Factores sociodemográficos en el riesgo de parto prematuro en gestantes del hospital Sergio Bernales en el período de 2019-2020

Objetivo. Determinar la relación de los factores sociodemográficos y el riesgo de parto prematuro en gestantes del hospital Sergio Bernales en el periodo de 2019-2020. Materiales y métodos. Estudio observacional, analítico, retrospectivo, y de casos-control, se buscará cuantificar la relación entre los factores sociodemográficos y el riesgo de parto prematuro. Se usará una revisión de historias clínicas correspondientes al servicio de Ginecología-Obstetricia del hospital Sergio Bernales. Los datos obtenidos se estudiarán mediante el programa SPSS y se buscará una asociación mediante análisis bivariado. Resultados. Del estudio de 300 gestantes, se realizó el análisis para 100 gestantes con diagnóstico de parto pretérmino que constituyeron los casos y 200 gestantes como grupo control. En el análisis bivariado se obtuvo que el parto pretérmino estuvo asociado a procedencia rural o extranjera (p<0.01); OR: 3.51 IC 95% = [ 2.03-6.06], edades extremas (p<0.01); OR: 2.72 con un IC 95% = [ 1.53-4.85], y no afiliada al SIS (p<0.03); OR: 2.59 con un IC 95% = [ 1.07-6.21]. Conclusiones. La procedencia rural o extranjera, edades extremas y no afiliada al SIS son factores asociados al riesgo de parto pretérmino.

Efectividad de un programa breve para la reducción de estrés en personal de salud durante el contexto de la pandemia COVID-19: Un estudio piloto

Objetivo. Determinar la influencia de un programa breve de reducción del estrés en trabajadores de salud del Instituto Nacional Materno perinatal durante la pandemia COVID-19. Materiales y Métodos. Esta investigación corresponde a un estudio cuasi experimental, que consiste en la elaboración y aplicación de un programa breve de reducción del estrés en trabajadores del área de Puericultura del INMP. La población estuvo conformada por 45 trabajadores, 30 de ellas cumplieron con los criterios de inclusión para el estudio piloto, de las cuales se distribuyó, por conveniencia, una muestra de 15 participantes para el grupo experimental y 15 para el grupo control. Se aplicó la Escala de Depresión, ansiedad y estrés (Dass21) al inicio de la investigación y luego de concluir con el programa. Se realizó el análisis de frecuencias y porcentajes de la variable, análisis de ajuste de bondad a la curva normal, y pruebas T Student para muestras relacionadas (p<0.05) pre y post test intragrupo con un nivel de confianza al 95%. Resultados.  Se encontró diferencias significativas en el grupo experimental en sus medidas pre y post tratamiento respectivamente en las variables Estrés (T=5.20, p<0.001, D=0.742, Dif medias=3.00); Ansiedad (T=3.15, p<0.007, D=0.414, Dif medias=2.20) y Depresión (T=3.97, p<0.001, D=0.426, Dif medias=3.97) reduciéndose las medias de dichas variables post aplicación del programa piloto. Conclusión. El programa breve para la reducción del estrés es efectivo para la reducción del estrés, a su vez debido a que en sus sesiones se entrenaron estrategias cognitivas conductuales para la mejora de la salud mental, se redujo, de forma secundaria, indicadores de ansiedad y depresión presentes en la muestra.

Mediators of socioeconomic inequalities in preterm birth: a systematic review

BACKGROUND

Rates of preterm birth are substantial with significant inequalities. Understanding the role of risk factors on the pathway from maternal socioeconomic status (SES) to preterm birth can help inform interventions and policy. This study therefore aimed to identify mediators of the relationship between maternal SES and preterm birth, assess the strength of evidence, and evaluate the quality of methods used to assess mediation.

METHODS

Using Scopus, Medline OVID, "Medline In Process & Other Non-Indexed Citation", PsycINFO, and Social Science Citation Index (via Web of Science), search terms combined variations on mediation, socioeconomic status, and preterm birth. Citation and advanced Google searches supplemented this. Inclusion criteria guided screening and selection of observational studies Jan-2000 to July-2020. The metric extracted was the proportion of socioeconomic inequality in preterm birth explained by each mediator (e.g. 'proportion eliminated'). Included studies were narratively synthesised.

RESULTS

Of 22 studies included, over one-half used cohort design. Most studies had potential measurement bias for mediators, and only two studies fully adjusted for key confounders. Eighteen studies found significant socioeconomic inequalities in preterm birth. Studies assessed six groups of potential mediators: maternal smoking; maternal mental health; maternal physical health (including body mass index (BMI)); maternal lifestyle (including alcohol consumption); healthcare; and working and environmental conditions. There was high confidence of smoking during pregnancy (most frequently examined mediator) and maternal physical health mediating inequalities in preterm birth. Significant residual inequalities frequently remained. Difference-of-coefficients between models was the most common mediation analysis approach, only six studies assessed exposure-mediator interaction, and only two considered causal assumptions.

CONCLUSIONS

The substantial socioeconomic inequalities in preterm birth are only partly explained by six groups of mediators that have been studied, particularly maternal smoking in pregnancy. There is, however, a large residual direct effect of SES evident in most studies. Despite the mediation analysis approaches used limiting our ability to make causal inference, these findings highlight potential ways of intervening to reduce such inequalities. A focus on modifiable socioeconomic determinants, such as reducing poverty and educational inequality, is probably necessary to address inequalities in preterm birth, alongside action on mediating pathways.

Inequalities in Birth Weight in Relation to Maternal Factors: A Population-Based Study of 3,813,757 Live Births

Background: Despite numerous studies of women having children later in life, evidence of the relationship between maternal factors and newborn outcomes in Central and Eastern European countries is limited. This study aimed to examine the association between maternal age, biological determinants, including parity and sex of the newborn, demographic and social background, and birth weight in 3.8 million singleton live births in Poland. Methods: The effect of maternal age on birth weight (in grams and Z-scores) adjusted for confounders was assessed using Generalized Linear Models. Results: The mean (±SD) birth weights of neonates born to primiparous women and multiparous women were 3356.3 ± 524.9 g and 3422.7 ± 538.6 g, respectively, which corresponded to a Z-score of −0.07 ± 0.96 and 0.14 ± 1.00, respectively (p ≤ 0.001). After controlling for biological, demographic, and social factors, a significant decrease in birth weight was found for primiparous women of the age group ≥30 years and multiparous women aged ≥35 years compared to the age group of 25–29 years. The lowest neonatal birth weight was observed in the case of women aged ≥45 years. Confounders did not affect birth weight Z-scores among primiparous women, whereas among multiparous women, together with educational factors, they reversed Z-scores from positive to negative values. The lower birth weight of neonates was overall associated with lower maternal education. Conclusions: Regardless of parity, advanced maternal age is strongly associated with a decreased neonatal birth weight, implying complications in early pregnancy and the antenatal period as well as obstetric complications. Counseling to support women’s family planning decisions and improving women’s education during their reproductive age may help to alleviate unfavorable newborn outcomes.

Maternal educational inequalities about adverse pregnancy outcomes observed in a rural area of a province of China during a time period (2010-2018)

BACKGROUND

The relationship between maternal education and adverse pregnancy outcomes is well documented. However, limited research has investigated maternal educational disparities in adverse pregnancy outcomes in China. This study examined maternal educational inequalities associated with adverse pregnancy outcomes in rural China.

METHODS

We conducted a population-based cohort study using participants enrolled in the National Free Preconception Health Examination Project in Yunnan province from 2010 to 2018. The primary outcome was stillbirth, and the secondary outcome was adverse pregnancy outcomes, defined as a composite event of stillbirth, preterm birth or low birth weight. The study was restricted to singleton births at 20-42 weeks' gestation. Univariate and multivariate log-binomial regression models were performed to estimate crude risk ratios (RRs) and confounding-adjusted RRs (ARRs) for stillbirth and adverse pregnancy outcomes according to maternal education level.

RESULTS

A total of 197 722 singleton births were included in the study. Compared with mid-educated women, low-educated women were at a significantly increased risk of stillbirth (ARR, 1.20; 95% CI, 1.05 to 1.38) and adverse pregnancy outcomes (ARR, 1.11; 95% CI, 1.07 to 1.16). However, the risk of stillbirth (ARR, 1.16; 95% CI, 1.01 to 1.35) was significantly higher for high-educated women compared with mid-educated women.

CONCLUSION

Compared with women with medium education level, women with lower education level were more likely to experience adverse pregnancy outcomes, including stillbirth, and women with higher education level were more likely to experience stillbirth.

The risk of preterm birth in combinations of socioeconomic position and mental health conditions in different age groups: a Danish nationwide register-based cohort study

Background

Inequality in preterm birth is a world-wide challenge that has proved difficult for maternity care services to meet. Reducing the inequality requires identification of pregnant women at particularly high risk of preterm birth in order to target interventions. Therefore, the aim was to estimate the risk of preterm birth in women with different combinations of socioeconomic position, mental health conditions, and age.

Methods

In this nationwide register-based cohort study, we included all first-time mothers that gave birth to a singleton liveborn infant in Denmark between 2000 and 2016. The absolute and relative risk of preterm birth (< 37 weeks of gestation) was examined in different combinations of educational level (high, intermediate, and low) and mental health conditions (no, minor, and moderate/severe) in three age strata (≤23, 24–30, and ≥ 31 years). We estimated the relative risk using Poisson regression with a robust error variance. As additive interaction can help identify subgroups where limited resources can be of best use, we measured the attributable proportion to assess the risk that is due to interaction of the different exposures.

Results

Of the 415,523 included first-time mothers, 6.3% gave birth prematurely. The risk of preterm birth increased with decreasing educational level and increasing severity of mental health conditions in all age strata, but most in women aged ≥31 years. The highest absolute risk was 12.9% [95% CI: 11.2;14.8%] in women aged ≥31 years with low education and moderate/severe mental health conditions resulting in a relative risk of 2.23 [95% CI: 1.93–2.58] compared to the unexposed reference group in that age strata. We found positive additive interaction between low education and mental health conditions in women aged 24–30 and ≥ 31 years and between age ≥ 31 years and combinations of mental health conditions and educational levels.

Conclusion

The inequality in preterm birth increased with increasing age. To reduce inequality in preterm birth focused attention on women with higher age further combined with lower educational levels and mental health conditions is essential.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-021-04138-0.

Social Determinants of Cigarette Smoking among American Women during Pregnancy

Educational attainment is among the most substantial protective factors against cigarette smoking, including during pregnancy. Although Minorities’ Diminished Returns (MDRs) of educational attainment, defined as weaker protective effect of education for racial and ethnic minority groups compared to Non-Hispanic Whites, has been demonstrated in previous studies; such MDRs are not tested for cigarette smoking during pregnancy. To better understand the relevance of MDRs to tobacco use during pregnancy, this study had three aims: firstly, to investigate the association between educational attainment and cigarette smoking in pregnant women; secondly, to compare racial and ethnic groups for the association between educational attainment and cigarette smoking; and thirdly, to explore the mediating effect of poverty status on such MDRs, among American adults during pregnancy. This cross-sectional study explored a nationally representative sample of pregnant American women (n = 338), which was taken from the Population Assessment of Tobacco and Health (PATH; 2013). Current smoking was the outcome. Educational attainment was the independent variable. Region and age were the covariates. Poverty status was the mediator. Race and ethnicity were the effect modifiers. Overall, a higher level of educational attainment (OR = 0.54, p < 0.05) was associated with lower odds of current smoking among pregnant women. Race (OR = 2.04, p < 0.05) and ethnicity (OR = 2.12, p < 0.05) both showed significant interactions with educational attainment on smoking, suggesting that the protective effect of educational attainment against smoking during pregnancy is smaller for Blacks and Hispanics than Non-Hispanic Whites. Poverty status fully mediated the above interactions. In the United States, highly educated pregnant Black and Hispanic women remain at higher risk of smoking cigarettes, possibly because they are more likely to live in poverty, compared to their White counterparts. The results suggest the role that labor market discrimination has in explaining lower returns of educational attainment in terms of less cigarette smoking by racial and ethnic minority pregnant women.