Sol Pia Juarez

Revisiting the Effect of Maternal Smoking during Pregnancy on Offspring Birthweight: A Quasi-Experimental Sibling Analysis in Sweden

Maternal smoking during pregnancy (SDP) seems associated with reduced birthweight in the offspring. This observation, however, is based on conventional epidemiological analyses, and it might be confounded by unobserved maternal characteristics related to both smoking habits and offspring birth weight. Therefore, we apply a quasi-experimental sibling analysis to revisit previous findings. Using the Swedish Medical Birth Register, we identified 677,922 singletons born between 2002 and 2010 from native Swedish mothers. From this population, we isolated 62,941 siblings from 28,768 mothers with discrepant habits of SDP. We applied conventional and mother-specific multilevel linear regression models to investigate the association between maternal SDP and offspring birthweight. Depending on the mother was light or heavy smoker and the timing of exposition during pregnancy (i.e., first or third trimester), the effect of smoking on birthweight reduction was between 6 and 78 g less marked in the sibling analysis than in the conventional analysis. Sibling analysis showed that continuous smoking reduces birthweight by 162 grams for mothers who were light smokers (1 to 9 cigarettes per day) and 226 g on average for those who were heavy smokers throughout the pregnancy in comparison to non-smoker mothers. Quitting smoking during pregnancy partly counteracted the smoking-related birthweight reduction by 1 to 29 g, and a subsequent smoking relapse during pregnancy reduced birthweight by 77 to 83 g. The sibling analysis provides strong evidence that maternal SDP reduces offspring birthweight, though this reduction was not as great as that observed in the conventional analysis. Our findings support public health interventions aimed to prevent SDP and to persuade those who already smoke to quit and not relapse throughout the pregnancy. Besides, further analyses are needed in order to explain the mechanisms through which smoking reduces birthweight and to identify other maternal characteristics that are common causes of both birthweight reduction and maternal smoking.

The Quality of Vital Statistics for Studying Perinatal Health: the Spanish Case

BACKGROUND Birthweight and gestational age are key indicators for perinatal health obtained through the birth certificate. Knowing the validity of birth certificate data is crucial when identifying needs and evaluating birth outcomes. In Spain, vital information is reported by parents and is not checked for consistency with any hospital document. Therefore, to perform a validation study and describe the variables associated with misreporting is essential to improve the quality of birth certificates. METHODS A database was created using birth information from hospital medical records that were individually linked with the Spanish National Institute of Statistics (INE) birth certificate files. Measures of reliability and validity were used to compare the data from the two sources. Logistic regression models were adjusted to model the odds of being misreported in birthweight and gestational age, controlling for relevant variables. RESULTS INE overestimated the prevalence of birthweight and gestational age. The degree of agreement between the two sources was good for most gestational age groups (Kappa = 0.74), very good for the very preterm (Kappa = 0.85) and very good also for all categories of birthweight (Kappa = 0.88). Misreporting was significantly higher among immigrants, unmarried mothers and girls. Being a preterm birth increased the odds of being declared with errors in gestational age; having low birthweight and missing information on gestational age were associated with misreporting birthweight. CONCLUSIONS The reliability of INE information could be greatly improved if hospitals included birthweight and gestational age on the document provided to parents for registering the 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.

Frecuencia de la cesárea en Andalucía: relación con factores sociales, clínicos y de los servicios sanitarios (2007-2009)

Background: Increasing trend and geographical variations in the use of caesarean section suggest the influence of non-clinical factors. The objective was to describe the use of caesarean section in the Andalusian region in Spain by exploring the role of social, clinical, and health services variables. Methods: A cross-sectional study was carried out using vital statistics. It involves all births occurred in Andalusia during the period of 2007-2009. The dependent variable was the use of caesarean section and the set of covariates were classified into three groups: those with a clinical meaning, those related to the health services organization, and those with a social significance. Multivariate logistic regressions were used. Results: In the data set of 293,558 births, the prevalence of caesarean delivery was 24.8%. The multivariate analysis highlights the labour complications as the clinical variable with the highest odds ratio (OR=19.36). Regarding the health services variables, the odds of experiencing a caesarean delivery were 55% higher on weekdays than on weekends. Cadiz was the province with the highest OR for caesarean section (comparison between Cadiz and Almeria: OR=1,21) where the ratio between births in public and private hospitals was 3.7. The frequency of caesarean section was 34% higher in women with third level education than those with no education. Conclusions: Labour complication is the most influential variable for caesarean section. Caesarean birth rate is above the accepted standards for all social classes and increases with educational level. Inter-provincial differences reflect different patterns with regard to the use of private medicine.

Does Maternal Country of Birth Matter for Understanding Offspring’s Birthweight? A Multilevel Analysis of Individual Heterogeneity in Sweden

Background Many public health and epidemiological studies have found differences between populations (e.g. maternal countries of birth) in average values of a health indicator (e.g. mean offspring birthweight). However, the approach based solely on population-level averages compromises our understanding of variability in individuals’ health around the averages. If this variability is high, the exclusive study of averages may give misleading information. This idea is relevant when investigating country of birth differences in health. Methods and Results To exemplify this concept, we use information from the Swedish Medical Birth Register (2002–2010) and apply multilevel regression analysis of birthweight, with babies (n = 811,329) at the first, mothers (n = 571,876) at the second, and maternal countries of birth (n = 109) at the third level. We disentangle offspring, maternal and maternal country of birth components of the total offspring heterogeneity in birthweight for babies born within the normal timespan (37–42 weeks). We found that of such birthweight variation about 50% was at the baby level, 47% at the maternal level and only 3% at the maternal countries of birth level. Conclusion In spite of seemingly large differences in average birthweight among maternal countries of birth (range 3290–3677g), knowledge of the maternal country of birth does not provide accurate information for ascertaining individual offspring birthweight because of the high inter-offspring heterogeneity around country averages. Our study exemplifies the need for a better understanding of individual health diversity for which group averages may provide insufficient and even misleading information. The analytical approach we outline is therefore relevant to investigations of country of birth (and ethnic) differences in health in general.

Too heavy, too late: investigating perinatal health outcomes in immigrants residing in Spain. A cross-sectional study (2009–2011)

Background Studies have shown that immigrants residing in Spain have lower risks of delivering low birthweight (LBW) and preterm babies despite their socioeconomic disadvantages (the healthy migrant paradox). However, less is known about other important perinatal outcomes derived from birth weight and gestational age such as macrosomia and post-term birth. This paper aims to compare the main indicators related to birth weight and gestational age (LBW, macrosomia, preterm and post-term) for immigrants and Spaniards. Methods Cross-sectional study based on the Spanish vital statistics for years 2009–2011. Multinomial regression models were performed to obtain crude and adjusted ORs and their 95% CIs. Results After adjusting for known confounders, compared with Spaniards, most immigrant groups show lower or not significantly different risks of delivering LBW (OR between 0.65 and 0.87) or, more exceptionally, preterm babies (between 0.75 and 0.93). However, most of them also show higher risks of delivering macrosomic (OR between 1.21 and 2.58) and post-term babies (OR between 1.11 and 1.50). Mothers from sub-Saharan Africa show a higher risk in all perinatal outcomes studied. Conclusions The immigrant health paradox should be carefully assessed in comprehensive terms. Together with a predominantly lower risk of LBW, most immigrants have a higher risk of macrosomia, post-term and preterm births. These results have policy-making implications since studying the right tail of the birth weight and gestational age distributions implies considering a different set of risk factors.

The Effect of Swedish Snuff (Snus) on Offspring Birthweight: A Sibling Analysis

Current observational evidence indicates that maternal smoking during pregnancy is associated with reduced birthweight in offspring. However, less is known about the effect of smokeless tobacco on birthweight and about the possible mechanisms involved in this relationship. This paper studies the effect of Swedish smokeless tobacco (snus) on offspring birthweight comparing the results obtained from a conventional linear regression analysis and from a quasi-experimental sibling design using a multilevel linear regression analysis. From the Swedish Medical Birth Register, we investigated 604,804 singletons born between 2002 and 2010. From them, we isolated 8,861 siblings from 4,104 mothers with discrepant snus-use habits (i.e., women who had at least one pregnancy during which they used snus and at least one other pregnancy in which they did not). The conventional analysis shows that continuous snus use throughout the pregnancy reduces birthweight in 47 g while quitting or relapsing snus has a minor and statistically non-significant effect (−6 g and −4 g, respectively). However, using a sibling analysis the effect observed for mothers who continue to use snus during pregnancy is less intense than that observed with previous conventional analyses (−20 g), and this effect is not statistically significant. Sibling analysis shows that quitting or relapsing snus use after the first trimester slightly reduces birthweight (14 g).However, this small change is not statistically significant. The sibling analysis provides strong causal evidence indicating that exposure to snus during pregnancy has a minor effect on birthweight reduction. Our findings provide a new piece of causal evidence concerning the effect of tobacco on birthweight and support the hypothesis that the harmful effect of smoking on birthweight is not mainly due to nicotine.

Questioning the Causal Link between Maternal Smoking during Pregnancy and Offspring Use of Psychotropic Medication: A Sibling Design Analysis.

A recent population-based, longitudinal study from Finland observed a dose-response association between smoking during pregnancy (SDP) and use of psychotropic medications in exposed children and young adults. However, this association may be confounded by unmeasured familial characteristics related to both SDP and offspring mental health. Consequently, we aim to investigate the effect of SDP by means of a sibling design that to some extent allows controlling for unknown environmental and genetic confounders. Using the Swedish Medical Birth Register (1987–1993), which was linked to the Swedish Prescribed Drugs Register (July 2005–December 2008), we investigated 579,543 children and among them 39, 007 were discordant for use of psychotropic medication and 4,021 siblings discordant for both use of psychotropic medication and for smoking exposure. Replicating the Finnish study using traditional logistic regression methods we found an association between exposure to ≥10 cigarettes per day during pregnancy and psychotropic drug use (odds ratio = 1.61, 95% confidence interval 1.56, 1.66). Similar in size to the association reported from Finland (odds ratio = 1.63; 95% confidence interval 1.53, 1.74). However, in the adjusted sibling analysis using conditional logistic regression, the association was considerably reduced (odds ratio 1.22; 95% confidence interval 1.08, 1.38). Preventing smoking is of major public health importance. However, SDP per se appears to have less influence on offspring psychotropic drug use than previously suggested.

From cradle to grave: tracking socioeconomic inequalities in mortality in a cohort of 11 868 men and women born in Uppsala, Sweden, 1915–1929

Background Ample evidence has shown that early-life social conditions are associated with mortality later in life. However, little attention has been given to the strength of these effects across specific age intervals from birth to old age. In this paper, we study the effect of the familys socioeconomic position and mothers marital status at birth on all-cause mortality at different age intervals in a Swedish cohort of 11 868 individuals followed across their lifespan. Methods Using the Uppsala Birth Cohort Multigenerational Study, we fitted Cox regression models to estimate age-varying HRs of all-cause mortality according to mothers marital status and familys socioeconomic position. Results Mothers marital status and familys socioeconomic position at birth were associated with higher mortality rates throughout life (HR 1.18 (95% CI 1.12 to 1.26) for unmarried mothers; 1.19 (95% CI 1.12 to 1.25) for low socioeconomic position). While the effect of familys socioeconomic position showed little variation across different age groups, the effect of marital status was stronger for infant mortality (HR 1.47 (95% CI 1.23 to 1.76); p=0.04 for heterogeneity). The results remained robust when early life and adult mediator variables were included. Conclusions Familys socioeconomic position and mothers marital status involve different dimensions of social stratification with independent effects on mortality throughout life. Our findings support the importance of improving early-life conditions in order to enhance healthy ageing.

Crisis económica al inicio del siglo xxi y mortalidad en España. Tendencia e impacto sobre las desigualdades sociales. Informe SESPAS 2014

This study aimed to assess the impact of the current economic crisis on mortality trends in Spain and its effect on social inequalities in mortality in Andalusia. We used data from vital statistics and the Population Register for 1999 to 2011, as provided by the Spanish Institute of Statistics, to estimate general and sex- and age-specific mortality rates. The Longitudinal Database of the Andalusian Population (2001 census cohort) was used to estimate general mortality rates and ratios by educational level. The annual percentages of change and trends were calculated using Joinpoint regressions. No significant change in the mortality trend was observed in Spain from 2008 onward. A downward trend after 1999 was confirmed for all causes and both sexes, with the exception of nervous system-related diseases. The reduction in mortality due to traffic accidents accelerated after 2003, while the negative trend in suicide was unchanged throughout the period studied. In Andalusia, social inequalities in mortality have increased among men since the beginning of the crisis, mainly due to a more intense reduction in mortality among persons with a higher educational level. Among women, no changes were observed in the pattern of inequality.