Educational inequalities in preterm and term small-for-gestational-age birth over time

Social inequalities in the provision of obstetric services in Norway 1967-2009: a population-based cohort study

Background

Socioeconomic (SE) inequalities have been observed in a number of adverse outcomes of pregnancy and many of the risk factors for such outcomes are associated with a low SE level. However, SE inequalities persist even after adjustment for these risk factors. Less well-off women are more vulnerable, but may also get less adequate health services. The objective of the present study was to assess possible associations between SE conditions in terms of maternal education as well as ethnic background and obstetric care.

Methods

A population-based national cohort study from the Medical Birth Registry of Norway. The study population comprised 2 305 780 births from the observation period 1967–2009. Multilevel analysis was used because of the hierarchical structure of the data. Outcome variables included induction of labour, epidural analgesia, caesarean section, neonatal intensive care and perinatal death.

Results

While medical interventions in the 1970s were employed less frequently in women of short education and non-western immigrants, this difference was eliminated or even reversed towards the end of the observation period. However, an excess perinatal mortality in both the short-educated [adjusted relative risk (aRR) = 2.49] and the non-western immigrant groups (aRR = 1.75) remained and may indicate increasing health problems in these groups.

Conclusion

Even though our study suggests a fair and favourable development during the last decades in the distribution across SE groups of obstetric health services, the results suggest that the needs for obstetric care have increased in vulnerable groups, requiring a closer follow-up.

Whether weather matters: Evidence of association between in utero meteorological exposures and foetal growth among Indigenous and non-Indigenous mothers in rural Uganda

Pregnancy and birth outcomes have been found to be sensitive to meteorological variation, yet few studies explore this relationship in sub-Saharan Africa where infant mortality rates are the highest in the world. We address this research gap by examining the association between meteorological factors and birth weight in a rural population in southwestern Uganda. Our study included hospital birth records (n = 3197) from 2012 to 2015, for which we extracted meteorological exposure data for the three trimesters preceding each birth. We used linear regression, controlling for key covariates, to estimate the timing, strength, and direction of meteorological effects on birth weight. Our results indicated that precipitation during the third trimester had a positive association with birth weight, with more frequent days of precipitation associated with higher birth weight: we observed a 3.1g (95% CI: 1.0–5.3g) increase in birth weight per additional day of exposure to rainfall over 5mm. Increases in average daily temperature during the third trimester were also associated with birth weight, with an increase of 41.8g (95% CI: 0.6–82.9g) per additional degree Celsius. When the sample was stratified by season of birth, only infants born between June and November experienced a significant associated between meteorological exposures and birth weight. The association of meteorological variation with foetal growth seemed to differ by ethnicity; effect sizes of meteorological were greater among an Indigenous subset of the population, in particular for variation in temperature. Effects in all populations in this study are higher than estimates of the African continental average, highlighting the heterogeneity in the vulnerability of infant health to meteorological variation in different contexts. Our results indicate that while there is an association between meteorological variation and birth weight, the magnitude of these associations may vary across ethnic groups with differential socioeconomic resources, with implications for interventions to reduce these gradients and offset the health impacts predicted under climate change.

Incidence of infants born small- and large-for-gestational-age in an Italian cohort over a 20-year period and associated risk factors

BACKGROUND

We assessed the incidence of infants born small-for-gestational-age (SGA) and large-for-gestational-age (LGA) in an Italian cohort over 20 years (1993-2013). Furthermore, we investigated maternal factors associated with SGA and LGA births.

METHODS

A retrospective review of obstetric records was performed on infants born in Chieti (Italy) covering every 5(th) year over a 20-year period, specifically examining data for 1993, 1998, 2003, 2008, and 2013. Infants with birthweight <10(th) percentile were defined as SGA, and those with birthweight >90(th) percentile as LGA. Data collected included newborn anthropometry, birth (multiple vs singleton), maternal anthropometry, previous miscarriage, gestational diabetes, hypertension, and smoking during pregnancy.

RESULTS

There were a pooled total of 5896 live births recorded across the 5 selected years. The number of SGA (+60.6 %) and LGA (+90.2 %) births increased considerably between 1993 and 2013. However, there were no marked changes in the incidence of SGA or LGA births (8.3 % and 10.8 % in 1993 versus 7.6 % and 11.7 % in 2013, respectively). Maternal factors associated with increased risk of SGA infants included hypertension, smoking, and previous miscarriage (all p < 0.05), while greater pre-pregnancy BMI and gestational diabetes were risk factors for LGA births (all p < 0.05).

CONCLUSIONS

There was an increase in the number of SGA and LGA births in Chieti over the last two decades, but there was little change in incidence over time. Most maternal factors associated with increased odds of SGA and LGA births were modifiable, thus incidence could be reduced by targeted interventions.

Temporal trends in social disparities in maternal smoking and breastfeeding in Canada, 1992-2008

A steady decrease in maternal smoking during pregnancy and a steady increase in breastfeeding rates have been observed in Canada in the past two decades. However, the extent to which all socioeconomic classes have benefited from this progress is unknown. Therefore, this study was undertaken to determine: (1) whether progress achieved benefited the entire population or was limited to specific strata; and (2) whether disparities among strata decreased, stayed the same, or increased over time. We used data from the National Longitudinal Survey of Children and Youth, which enrolled children aged 0-3 years between 1994 and 2008. Data collected at entry was analyzed in a cross-sectional manner. Between birth years 1992-1996 and 2005-2008, smoking during pregnancy decreased from 11.5 % (95 % CI 10.0-13.0 %) to 5.2 % (95 % CI 4.1-6.3 %) among mothers with a college or university degree and from 43.0 % (95 % CI 38.8-47.2 %) to 38.6 % (95 % CI 32.9-44.2 %) among those with less than secondary education. During the same period, the rate of breastfeeding initiation increased from 83.8 % (95 % CI 81.9-85.6 %) to 91.5 % (95 % CI 90.2-92.8 %) among mothers with a college or university degree and from 63.1 % (95 % CI 58.9-67.4 %) to 74.7 % (95 % CI 69.8-79.7 %) among those with less than secondary education. The risks of smoking and of not breastfeeding remained significantly higher in the least educated category than in the most educated throughout the study period, and these associations remained statistically significant after controlling for maternal age. Gaps between the least and the most educated mothers narrowed for breastfeeding but widened for smoking during pregnancy.

Fetuses-at-risk, to avoid paradoxical associations at early gestational ages: extension to preterm infant mortality

BACKGROUND

Fetuses-at-risk denominators are commonly used in research on preterm stillbirth, but applications to postnatal outcomes such as preterm infant mortality are controversial. We evaluated whether biased associations between maternal risk factors and preterm infant mortality caused by stratification by preterm birth could be avoided using fetuses-at-risk risk ratios.

METHODS

Data included 3 277 570 births drawn from the linked live birth-death file for Canada from 1990 through 2005. We used maternal age as the risk factor, and estimated the association with stillbirth, early neonatal, late neonatal and postneonatal mortality by gestational interval (22-24, 25-27, 28-31, 32-36, ≥37 weeks). Models were run using (i) log-binomial regression stratified by preterm gestational age, and (ii) unstratified log-binomial regression using fetuses-at-risk denominators.

RESULTS

Extremes of maternal age were associated with higher mortality among term births. Among preterm births, the stratified model suggested a protective, null or attenuated association of extremes of maternal age with stillbirth, early, late and post neonatal mortality. The unstratified fetuses-at-risk model, however, resulted in the expected higher risk of mortality at extremes of maternal age for all outcomes.

CONCLUSIONS

Fetuses-at-risk regression can avoid paradoxical associations between maternal exposures and mortality of infants born early in gestation, caused by preterm birth stratification bias. The fetuses-at-risk approach can be extended through the first year of life, or potentially beyond, depending on the outcome and presence of unmeasured confounders associated with preterm birth.

Applying measures of discriminatory accuracy to revisit traditional risk factors for being small for gestational age in Sweden: a national cross-sectional study

OBJECTIVES

Small for gestational age (SGA) is considered as an indicator of intrauterine growth restriction, and multiple maternal and newborn characteristics have been identified as risk factors for SGA. This knowledge is mainly based on measures of average association (ie, OR) that quantify differences in average risk between exposed and unexposed groups. Nevertheless, average associations do not assess the discriminatory accuracy of the risk factors (ie, its ability to discriminate the babies who will develop SGA from those that will not). Therefore, applying measures of discriminatory accuracy rather than measures of association only, our study revisits known risk factors of SGA and discusses their role from a public health perspective.

DESIGN

Cross-sectional study. We measured maternal (ie, smoking, hypertension, age, marital status, education) and delivery (ie, sex, gestational age, birth order) characteristics and performed logistic regression models to estimate both ORs and measures of discriminatory accuracy, like the area under the receiver operating characteristic curve (AU-ROC) and the net reclassification improvement.

SETTING

Data were obtained from the Swedish Medical Birth Registry.

PARTICIPANTS

Our sample included 731 989 babies born during 1987-1993.

RESULTS

We replicated the expected associations. For instance, smoking (OR=2.57), having had a previous SGA baby (OR=5.48) and hypertension (OR=4.02) were strongly associated with SGA. However, they show a very small discriminatory accuracy (AU-ROC≈0.5). The discriminatory accuracy increased, but remained unsatisfactorily low (AU-ROC=0.6), when including all variables studied in the same model.

CONCLUSIONS

Traditional risk factors for SGA alone or in combination have a low accuracy for discriminating babies with SGA from those without SGA. A proper understanding of these findings is of fundamental relevance to address future research and to design policymaking recommendations in a more informed way.

Patient versus professional based psychosocial risk factor screening for adverse pregnancy outcomes

To identify Psychopathology, Psychosocial problems and substance use (PPS) as predictors of adverse pregnancy outcomes, two screen-and-advice instruments were developed: Mind2Care (M2C, self-report) and Rotterdam Reproductive Risk Reduction (R4U, professional's checklist). To decide on the best clinical approach of these risks, the performance of both instruments was compared. Observational study of 164 pregnant women who booked at two midwifery practices in Rotterdam. Women were consecutively screened with M2C and R4U. For referral to tailored care based on specific PPS risks, inter-test agreement of single risks was performed in terms of overall accuracy and positive accuracy (risk present according to both instruments). With univariate regression analysis we explored determinants of poor agreement (<90 %). For triage based on risk accumulation and for detecting women-at-risk for adverse birth outcomes, M2C and R4U sum scores were compared. Overall accuracy of single risks was high (mean 93 %). Positive accuracy was lower (mean 46 %) with poorest accuracy for current psychiatric symptoms. Educational level and ethnicity partly explained poor accuracy (p < 0.05). Overall low PPS prevalence decreased the statistical power. For triage, M2C and R4U sum scores were interchangeable from sum scores of five or more (difference <1 %). The probability of adverse birth outcomes similarly increased with risk accumulation for both instruments, identifying 55-75 % of women-at-risk. The self-report M2C and the professional's R4U checklist seem interchangeable for triage of women-at-risk for PPS or adverse birth outcomes. However, the instruments seem to provide complementary information if used as a guidance to tailored risk-specific care.

Contribution of local area deprivation to cultural-linguistic inequalities in foetal growth restriction: trends over time in a Canadian metropolitan centre

This study investigated temporal trends in heterogeneity of foetal growth restriction across neighbourhood deprivation levels for two culturally distinct communities (Anglophones and Francophones) in a North American metropolitan centre. Inequalities in foetal growth restriction related to deprivation fell from 1989 to 2008 for Francophones, but initial improvements for Anglophones later reversed with a rise in poor foetal growth in the most materially disadvantaged and, unexpectedly, advantaged areas as well. Inequalities in foetal growth restriction related to neighbourhood material deprivation may be emerging in this minority Anglophone population. Potential mechanisms underlying these trends are discussed, as well as implications for perinatal health policy.

Neighbourhood income and neonatal, postneonatal and sudden infant death syndrome (SIDS) mortality in Canada, 1991-2005

BACKGROUND

Rates of infant mortality declined in Canada in the 1990s and 2000s, but the extent to which all socio-economic levels benefitted from this progress is unknown.

OBJECTIVES

This study investigated differences and time trends in neonatal, postneonatal and sudden infant death syndrome (SIDS) mortality across neighbourhood income quintiles among live births in Canada from 1991 through 2005.

METHODS

The Canadian linked live birth and infant death file was used, excluding births from Ontario, Yukon, Northwest Territories and Nunavut. Mortality rates for neonatal, postneonatal and sudden infant death syndrome (SIDS) were calculated by neighbourhood income quintile and period (1991-1995, 1996-2000, 2001-2005). Hazard ratios (HR) for neighbourhood income quintile and period were computed, adjusting for province of residence, maternal age, parity, infant sex and multiple birth.

RESULTS

In urban areas, for the entire study period (1991-2005), the poorest neighbourhood income quintile had a higher hazard of neonatal death (adjusted HR 1.24, 95% CI 1.15-1.34), postneonatal death (adjusted HR 1.58, 95% CI 1.41-1.76) and SIDS (adjusted HR 1.83, 95% CI 1.49-2.26) compared to the richest quintile. Postneonatal and SIDS mortality rates declined by 37% and 57%, respectively, between 1991-1995 and 2001-2005 whereas no significant change was observed in neonatal mortality. The decrease in postneonatal and SIDS mortality rates occurred across all income quintiles.

CONCLUSION

This study shows that despite a decrease in infant mortality and SIDS across all neighbourhood income quintiles over time in Canada, socio-economic inequalities persist. This finding highlights the need for effective infant health promotion strategies in vulnerable populations.