Economic stress or random variation? Revisiting German reunification as a natural experiment to investigate the effect of economic contraction on sex ratios at birth

Schnettler, Sebastian; Klüsener, Sebastian

doi:10.1186/1476-069x-13-117

Cited by 16 publications

(13 citation statements)

References 58 publications

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“…Decreased male survival in utero in the context of poor maternal conditions has been observed in other mammals (64), and population-level data suggest that the relative number of male births tends to decrease in the context of maternal exposure to earthquakes and social upheaval, including President Kennedy's assassination and the 9/11 terrorist attacks in New York (31)(32)(33)(34)(35)(36). Diminished male fetal survival is poorly understood (59) and not without controversy (38,39). SSR stress-related effects are frequently interpreted via evolutionary models as a process of "culling the weak" so that the fittest procreate (37) as well as supported by DOHaD research on prenatal programming which shows early male vulnerability proximal to the in utero exposure (65).…”

Section: Discussionmentioning

confidence: 99%

“…in the SSR is debated (38,39), most agree that a dynamic expression of the SSR allows for evolutionary response to natural selection pressures (6) and that males are more vulnerable to in utero perturbations (40). The tendency for more PTBs among males (41,42), and males' increased risk for early neurodevelopmental disorders such as intellectual disability, autism, dyslexia, and ADHD (37,40) and greater likelihood of telomere shortening (43) support this assertion.…”

Section: Significancementioning

confidence: 99%

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Maternal prenatal stress phenotypes associate with fetal neurodevelopment and birth outcomes

Walsh

McCormack

Webster

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

169

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Maternal prenatal stress influences offspring neurodevelopment and birth outcomes including the ratio of males to females born; however, there is limited understanding of what types of stress matter, and for whom. Using a data-driven approach with 27 variables from questionnaires, ambulatory diaries, and physical assessments collected early in the singleton pregnancies of 187 women, 3 latent profiles of maternal prenatal stress emerged that were differentially associated with sex at birth, birth outcomes, and fetal neurodevelopment. Most women (66.8%) were in the healthy group (HG); 17.1% were in the psychologically stressed group (PSYG), evidencing clinically meaningful elevations in perceived stress, depression, and anxiety; and 16% were in the physically stressed group (PHSG) with relatively higher ambulatory blood pressure and increased caloric intake. The population normative male:female secondary sex ratio (105:100) was lower in the PSYG (2:3) and PHSG (4:9), and higher in the HG (23:18), consistent with research showing diminished male births in maternal stress contexts. PHSG versus HG infants were born 1.5 wk earlier (P < 0.05) with 22% compared to 5% born preterm. PHSG versus HG fetuses had decreased fetal heart rate–movement coupling (P < 0.05), which may indicate slower central nervous system development, and PSYG versus PHSG fetuses had more birth complications, consistent with previous findings among offspring of women with psychiatric illness. Social support most strongly differentiated the HG, PSYG, and PHSG groups, and higher social support was associated with increased odds of male versus female births. Stress phenotypes in pregnant women are associated with male vulnerability and poor fetal outcomes.

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Section: Discussionmentioning

confidence: 99%

Section: Significancementioning

confidence: 99%

Maternal prenatal stress phenotypes associate with fetal neurodevelopment and birth outcomes

Walsh

McCormack

Webster

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

169

View full text Add to dashboard Cite

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“…With German reunification in 1990, the West German institutional model was installed in the East and set the former GDR on a difficult path of transition to a democratic market economy. The reunification is often framed as a quasi-experiment (e.g., Fasang 2014; Schnettler and Klüsener 2014; Struffolino et al 2016). This is problematic for several reasons.…”

Section: Example Application To Employment Life-courses In East Germamentioning

confidence: 99%

Comparing Groups of Life-Course Sequences Using the Bayesian Information Criterion and the Likelihood-Ratio Test

Liao

Fasang

2020

Sociological Methodology

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How can we statistically assess differences in groups of life-course trajectories? The authors address a long-standing inadequacy of social sequence analysis by proposing an adaption of the Bayesian information criterion (BIC) and the likelihood-ratio test (LRT) for assessing differences in groups of sequence data. Unlike previous methods, this adaption provides a useful measure for degrees of difference, that is, the substantive significance, and the statistical significance of differences between predefined groups of life-course trajectories. The authors present a simulation study and an empirical application on whether employment life-courses converged after reunification in the former East Germany and West Germany, using data for six birth-cohort groups ages 15 to 40 years from the German National Education Panel Study. The new methods allow the authors to show that convergence of employment life-courses around reunification was stronger for men than for women and that it was most pronounced in terms of the duration of employment states but weaker for their order and timing in the life-course. Convergence of East German and West German women’s employment lives set in earlier and reflects a secular trend toward a more gender-egalitarian division of labor in West Germany that is unrelated to reunification. The simulation study and the substantive application demonstrate the usefulness of the proposed BIC and LRT methods for assessing group differences in sequence data.

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“…Not all existing research, however, provides supporting evidence for the hypothesis. A number of studies have questioned the previous findings of SRB declines during times of wars ( Graffelman and Hoekstra, 2000 ; Polasek et al , 2005 ; Polasek, 2006 ), political upheavals ( Schnettler and Klüsener, 2014 ) and famines ( Zhao et al , 2013 ). These equivocal results indicate that the relationship between SRB changes and idiosyncratic shocks is sensitive to data and the context under study ( James, 2009 ).…”

Section: Introductionmentioning

confidence: 97%

Maternal stress and sex ratio at birth in Sweden over two and a half centuries: a retest of the Trivers–Willard hypothesis

2021

Human Reproduction

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STUDY QUESTION Is there a negative relationship, as predicted in the Trivers–Willard hypothesis (TWH), between the intensity of maternal stress and sex ratio at birth (SRB)? SUMMARY ANSWER Using a comprehensive data set with multiple indicators of maternal stress, most measures of stress show no statistically significant association with SRB over a period spanning 243 years, indicating no support for the TWH. WHAT IS KNOWN ALREADY Evolutionary biologists have proposed a widely discussed hypothesis that women in poor and stressful conditions during pregnancy are more likely to give birth to girls, and exposure to stressful events may therefore lead to a reduction in sex (male-to-female) ratio at birth. The empirical evidence so far is mixed. STUDY DESIGN, SIZE, DURATION Annual time series data, spanning 243 years between 1749 and 1991 for Sweden at the national level, were drawn from multiple sources. The outcome is defined as the percentage of male births relative to all births in Sweden in a given year. The covariates include a set of economic and climatic variables as proxies for maternal stress. PARTICIPANTS/MATERIALS, SETTING, METHODS We conduct a series of ARIMA (autoregressive integrated moving average) models to examine the relationship between maternal stress and SRB during three periods: 1749–1991, 1749–1861 and 1862–1991. MAIN RESULTS AND THE ROLE OF CHANCE In 1749–1991, economic proxies for maternal stress showed no statistically significant association with SRB. In 1749–1861, two indicators were significantly associated with SRB, but the coefficients were opposite in direction to the TWH. In 1862–1991, five out of six covariates showed no significant association with SRB. An additional analysis found no significant correlation between sex ratio of stillbirths and all covariates in 1862–1991. Our results are incompatible with the TWH and suggest that previous findings in support of the TWH are not robust. LIMITATIONS, REASONS FOR CAUTION This study provides population-level evidence that may not necessarily reflect the nature of all individuals due to the ecological fallacy. The time series analysed in this study are annual data, and we cannot examine the potential seasonality due to the lack of disaggregated monthly data. Our findings may not be generalised to the contexts of extreme maternal stress conditions such as famine and war. WIDER IMPLICATIONS OF THE FINDINGS The results from existing studies in this topic may be speculative, and additional research with more comprehensive design, data and covariates is needed to reconsider the robustness of previous findings. STUDY FUNDING/COMPETING INTEREST(S) The author receives no external funding and has no conflict of interest to declare. TRIAL REGISTRATION NUMBER N/A.

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Economic stress or random variation? Revisiting German reunification as a natural experiment to investigate the effect of economic contraction on sex ratios at birth

Cited by 16 publications

References 58 publications

Maternal prenatal stress phenotypes associate with fetal neurodevelopment and birth outcomes

Maternal prenatal stress phenotypes associate with fetal neurodevelopment and birth outcomes

Comparing Groups of Life-Course Sequences Using the Bayesian Information Criterion and the Likelihood-Ratio Test

Maternal stress and sex ratio at birth in Sweden over two and a half centuries: a retest of the Trivers–Willard hypothesis

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