Saturday, November 24, 2012
Tim Bruckner & Jenna Nobles
Social Science & Medicine, forthcoming
Empirical research and the theory of natural selection assert that male mortality more than female mortality responds to ambient stressors in utero. Although population stressors may adversely damage males that survive to birth, the rival culled cohort hypothesis contends that males born during stressful times may exhibit better health than males in other cohorts because fetal loss has "culled" the frailest males. We tested these hypotheses by examining child developmental outcomes in a U.S. birth cohort reportedly affected in utero by the September 11, 2001 attacks. We used as outcomes the Bayley cognitive score and child height-for-age from the Early Childhood Longitudinal Study-Birth Cohort. Previous research demonstrates a male-specific effect of 9/11 on California infants born in December 2001. We, therefore, compared cognition and height of this cohort with males born prior to the 9/11 attacks. We controlled for unobserved confounding across gender, season, and region by using triple-difference regression models (N=6,950). At 24 months, California males born in December scored greater than expected in cognitive ability (coef= 9.55, standard error = 3.37; p = .004). We observed no relation with height. Results remained robust to alternative specifications. Findings offer partial support for the culled cohort hypothesis in that we observed greater than expected cognitive scores at two years of age among a cohort of males affected by 9/11 in utero. Contemporary population stressors may induce male-specific culling, thereby resulting in relatively improved development among males that survive to birth.
Dierk Herzer, Holger Strulik & Sebastian Vollmer
Journal of Economic Growth, December 2012, Pages 357-385
We examine the long-run relationship between fertility, mortality, and income using panel cointegration techniques and the available data for the last century. Our main result is that mortality changes and growth of income contributed to the fertility transition. The fertility reduction triggered by falling mortality, however, is not enough to overcompensate the positive effect of falling mortality on population growth. This means that growth of income per capita is essential to explain the observed secular decline of population growth. These results are robust to alternative estimation methods, potential outliers, sample selection, different measures of mortality, the sample period, the inclusion of education as an explanatory variable, and the use of different data sets. In addition, our causality tests suggest that fertility changes are both cause and consequence of economic development.
Julia Steinberg & Jeanne Tschann
Social Science & Medicine, forthcoming
Although many studies have found an association between childhood adversities and mental health problems, few have examined whether childhood adversities are linked to having abortions. This research investigates the association between a range of childhood adversities and risk of abortion in part to identify which adversities should be considered when examining the association between abortion and subsequent mental health. Using the U.S. National Comorbidity Survey-Replication (NCS-R), we tested the association between 10 childhood adversities and risk of 0, 1, or multiple abortions among 1,511 U.S. women ages 18 to 41. We employed multinomial logistic regression to also examine the independent association between each childhood adversity and number of subsequent abortions, controlling for sociodemographic factors, total number of pregnancies, end each adversity. Women who had experienced two or more personal safety threats, one parental mental illness, or two or more parental mental illnesses were more likely to have multiple versus no abortions [OR = 9.87, 95% CI: 2.45-39.72; OR = 2.81, 95% CI: 1.27-6.21; OR = 5.28, 95% CI: 1.60-17.38, respectively], and multiple versus one abortion [OR = 13.33, 95% CI: 2.48-71.68; OR = 2.17, 95% CI: 1.03-4.56; OR = 3.67, 95% CI: 1.15-11.76, respectively]. Women who had experienced childhood physical abuse were more likely to have one compared to no abortions [OR = 2.00; 1.19-3.34]. These results suggest that some childhood adversities may partially explain the association between abortion and mental health. Accordingly, they should be considered in future research examining the link between abortion and mental health.
Katherine Legare et al.
American Journal of Public Health, November 2012, Pages e45-e47
We conducted a telephone survey of pharmacies in 2 New York City neighborhoods on same-day availability, type, and cost of over-the-counter emergency contraception. There was no difference in availability of over-the-counter emergency contraception between Upper East Side and East Harlem pharmacies (93% vs 94%; P = .71). Average cost of medication was less in East Harlem than in the Upper East Side ($45.16 vs $51.64; P < .001). Efforts should accentuate overcoming cost and knowledge barriers associated with the use of emergency contraception.
Joseph Potter et al.
Perspectives on Sexual and Reproductive Health, forthcoming
Context: Sterilization is the most commonly used contraceptive in the United States, yet access to this method is limited for some.
Methods: A 2006-2008 prospective study of low-income pill users in El Paso, Texas, assessed unmet demand for sterilization among 801 women with at least one child. Multivariable logistic regression analysis identified characteristics associated with wanting sterilization. In 2010, at an 18-month follow-up, women who had wanted sterilization were recontacted; 120 semistructured and seven in-depth interviews were conducted to assess motivations for undergoing the procedure and the barriers faced in trying to obtain it.
Results: At baseline, 56% of women wanted no more children; at nine months, 65% wanted no more children, and of these, 72% wanted sterilization. Only five of the women interviewed at 18 months had undergone sterilization; two said their partners had obtained a vasectomy. Women who had not undergone sterilization were still strongly motivated to do so, mainly because they wanted no more children and were concerned about long-term pill use. Among women's reasons for not having undergone sterilization after their last pregnancy were not having signed the Medicaid consent form in time and having been told that they were too young or there was no funding for the procedure.
Conclusions: Because access to a full range of contraceptive methods is limited for low-income women, researchers and providers should not assume a woman's current method is her method of choice.
Journal of Public Health, December 2012, Pages 609-614
Background: In 1999, the UK Government launched a strategy to reduce teenage pregnancy and geographical inequalities in teenage conception rates. This study investigates how associations between deprivation and under-18 conceptions, along with subsequent abortions, since changed as teenage pregnancy rates fell.
Methods: A data set was constructed from local authority Indices of Multiple Deprivation (IMD) scores and routine data on under-18 conception rates and the proportion of under-18 conceptions leading to abortion from 1998 to 2010. Correlation analysis (Pearson's r) was used to measure the association between each period of conception and abortion data and the relevant version of the IMD. Changes in these correlations over the period were tested for statistical significance.
Results: There remained a strong association between IMD and under-18 conception rates from 1998 (r = 0.782, P< 0.0001) to 2010 (r = 0.817, P< 0.0001) with no statistically significant change. A statistically significant decrease occurred in the inverse association between IMD and the proportion of under-18 conceptions leading to abortion from 1998 (r = -0.501, P< 0.0001) to 2010 (r = -0.332, P< 0.0001)
Conclusions: While under-18 conceptions fell from 1998 to 2010, inequalities in rates between the most and least deprived local authorities remained undiminished. At the same time, abortion became an increasingly common outcome of under-18 conceptions.
Paola Bressan & Stefania Dal Pos
Archives of Sexual Behavior, December 2012, Pages 1423-1430
Even after they have taken all reasonable measures to decrease the probability that their spouses cheat on them, men still face paternal uncertainty. Such uncertainty can lead to paternal disinvestment, which reduces the children's probability to survive and reproduce, and thus the reproductive success of the fathers themselves. A theoretical model shows that, other things being equal, men who feel confident that they have fathered their spouses' offspring tend to enjoy greater fitness (i.e., leave a larger number of surviving progeny) than men who do not. This implies that fathers should benefit from exaggerating paternal resemblance. We argue that the self-deceiving component of this bias could be concealed by generalizing this resemblance estimation boost to (1) family pairs other than father-child and (2) strangers. Here, we tested the prediction that fathers may see, in unrelated children's faces, stronger family resemblances than non-fathers. In Study 1, 70 men and 70 women estimated facial resemblances between children paired, at three different ages (as infants, children, and adolescents), either to themselves or to their parents. In Study 2, 70 men and 70 women guessed the true parents of the same children among a set of adults. Men who were fathers reported stronger similarities between faces than non-fathers, mothers, and non-mothers did, but were no better at identifying childrens' real parents. We suggest that, in fathers, processing of facial resemblances is biased in a manner that reflects their (adaptive) wishful thinking that fathers and children are related.
Kristjana Einarsdóttir et al.
PLoS ONE, November 2012
Background: The Australian baby bonus maternity payment introduced in 2004 has been reported to have successfully increased fertility rates in Australia. We aimed to investigate the influence of the baby bonus on maternal demographics and birth characteristics in Western Australia (WA).
Methods and Findings: This study included 200,659 birth admissions from WA during 2001-2008, identified from administrative birth and hospital data-systems held by the WA Department of Health. We estimated average quarterly birth rates after the baby bonus introduction and compared them with expected rates had the policy not occurred. Rate and percentage differences (including 95% confidence intervals) were estimated separately by maternal demographics and birth characteristics. WA birth rates increased by 12.8% following the baby bonus implementation with the greatest increase being in mothers aged 20-24 years (26.3%, 95%CI = 22.0,30.6), mothers having their third (1.6%, 95%CI = 0.9,2.4) or fourth child (2.2%, 95%CI = 2.1,2.4), mothers living in outer regional and remote areas (32.4%, 95%CI = 30.2,34.6), mothers giving birth as public patients (1.5%, 95%CI = 1.3,1.8), and mothers giving birth in public hospitals (3.5%, 95%CI = 2.6,4.5). Interestingly, births to private patients (-4.3%, 95%CI = -4.8,-3.7) and births in private hospitals (-6.3%, 95%CI = -6.8,-5.8) decreased following the policy implementation.
Conclusions: The introduction of the baby bonus maternity payment may have served as an incentive for women in their early twenties and mothers having their third or fourth child and may have contributed to the ongoing pressure and staff shortages in Australian public hospitals, particularly those in outer regional and remote areas.
Michael Neugart & Henry Ohlsson
Journal of Population Economics, January 2013, Pages 87-108
Economic theory suggests that incentives matter for people's decisions. This paper investigates whether this also holds for less self-evident areas of life such as the timing of births. We use a natural experiment when the German government changed its parental benefit system on January 1, 2007. The policy change strongly increased economic incentives for women to postpone delivery provided that they were employed. Applying a difference-in-difference-in-difference approach, we find very strong evidence that women with an employment history near to the end of their term indeed succeeded to shift births to the New Year and, therefore, could benefit from the new and more generous parental benefit system. Suggesting a model of chain reactions, we also report evidence that some women with due dates earlier in December tried but did not succeed to shift births to the New Year.
David Lawson, Alexandra Alvergne & Mhairi Gibson
Proceedings of the Royal Society: Biological Sciences, 7 December 2012, Pages 4755-4764
Evolutionary models of human reproduction argue that variation in fertility can be understood as the local optimization of a life-history trade-off between offspring quantity and ‘quality'. Child survival is a fundamental dimension of quality in these models as early-life mortality represents a crucial selective bottleneck in human evolution. This perspective is well-rehearsed, but current literature presents mixed evidence for a trade-off between fertility and child survival, and little empirical ground to evaluate how socioecological and individual characteristics influence the benefits of fertility limitation. By compiling demographic survey data, we demonstrate robust negative relationships between fertility and child survival across 27 sub-Saharan African countries. Our analyses suggest this relationship is primarily accounted for by offspring competition for parental investment, rather than by reverse causal mechanisms. We also find that the trade-off increases in relative magnitude as national mortality declines and maternal somatic (height) and extrasomatic (education) capital increase. This supports the idea that socioeconomic development, and associated reductions in extrinsic child mortality, favour reduced fertility by increasing the relative returns to parental investment. Observed fertility, however, falls considerably short of predicted optima for maximizing total offspring survivorship, strongly suggesting that additional unmeasured costs of reproduction ultimately constrain the evolution of human family size.
Eva Mörk, Anna Sjögren & Helena Svaleryd
Journal of Population Economics, January 2013, Pages 33-65
Exploiting the exogenous variation in user fees caused by a Swedish childcare reform, we are able to identify the causal effect of childcare costs on fertility in a context in which childcare enrollment is almost universal, user fees are low, and labor force participation of mothers is very high. Anticipation of a reduction in childcare costs increased the number of first and higher-order births, but only seemed to affect the timing of second births. For families with many children we also find a marginally significant negative income effect on fertility.
Abigail Aiken, Jacqueline Angel & Toni Miles
American Journal of Public Health, December 2012, Pages 2330-2335
Objectives: We investigated the relationship between the number of times a woman has been pregnant and walking difficulty in later life.
Methods: With data from the Hispanic Established Populations for Epidemiologic Studies of the Elderly, a representative population-based cohort of Mexican Americans aged 65 years and older residing in 5 Southwestern states, we measured walking difficulty using 2 items from the performance-oriented mobility assessments: the timed walk and seated chair rise.
Results: We observed significantly higher rates of ambulatory limitation among women with 6 or more pregnancies than among women with 4 or fewer pregnancies: 44.9% and 27.0%, respectively, were unable to perform or performed poorly in the seated chair rise and timed walk. Ordinal logistic regression models show that gravidity predicts level of performance in both mobility tasks and that higher gravidity is associated with worse performance, even after adjustment for both age and chronic disease.
Conclusions: Gravidity is a risk factor for ambulatory limitation in old age. A life course approach to reproduction in public health research and practice is warranted.
Sociological Forum, December 2012, Pages 913-936
This article seeks to demonstrate and analyze the cultural and emotional work surrogate mothers collectively engage in on the largest surrogacy support website, http://www.surromomsonline.com . Surrogate mothers' online stories and discussions frame contract surrogacy as a "labor of love." Women often describe their surrogacy as a "journey" of shared love; they hope for a lasting relationship with the couple they carry for. This article explores how the language of love, learned and internalized through online communication with other surrogates, creates both a cultural conceptualization of surrogacy and a ground for action. Love and altruistic giving are consistent with close interpersonal rather than market relationships; surrogates hope for a long-term friendship with their couple. Surrogacy journeys, however, not infrequently end in disappointment; surrogates feel betrayed when couples cut ties. As a result of collective learning, surrogates' discussions increasingly articulate the position that love, even when unreciprocated, can lead to repeated giving; love is noble and ennobling. Surrogates find appreciation and support in their online surrogacy community where they agree that giving life is a moral good. This stance has contributed to a renewed enthusiasm to bear children for others.
Arthur Robson, Balazs Szentes & Emil Iantchev
American Economic Journal: Microeconomics, November 2012, Pages 172-201
We consider the evolutionary basis of time discounting with intergenerational transfers. We show that the notion of "reproductive value" from biology provides the utility criterion for a parent to optimize the allocation of resources between transfers to offspring and to promote her own survival. This optimization has a natural dynamic programming formulation. We show that younger individuals may well be "too impatient," but older individuals "too patient" in accordance with observations. We compare the allocation of resources under sexual reproduction to that where there is asexual reproduction. Sex distorts time discounting; under plausible conditions, sex increases patience.
J. Prescott et al.
Human Reproduction, December 2012, Pages 3622-3631
Study question: Is the association between paternal age at birth and offspring leukocyte telomere length (LTL) an artifact of early life socioeconomic status (SES)?
Summary answer: Indicators of early life SES did not alter the relationship between paternal age at birth and offspring LTL among a population of white female nurses.
Study design, size and duration: The Nurses' Health Study (NHS) is an ongoing prospective cohort study of 121 700 female registered nurses who were enrolled in 1976. Great effort goes into maintaining a high degree of follow-up among our cohort participants (>95% of potential person-years). In 1989-1990, a subset of 32 826 women provided blood samples from which we selected participants for several nested case-control studies of telomere length and incident chronic disease. We used existing LTL data on a total of 4250 disease-free women who also reported maternal and paternal age at birth for this study.
Participants/materials, setting and methods: Nested case-control studies of stroke, myocardial infarction, cancers of the breast, endometrium, skin, pancreas and colon, as well as colon adenoma, were conducted within the blood sub-cohort. Each study used the following study design: for each case of a disease diagnosed after blood collection, a risk-set sampling scheme was used to select from one to three controls from the remaining participants in the blood sub-cohort who were free of that disease when the case was diagnosed. Controls were matched to cases by age at blood collection (±1 year), date of blood collection (±3 months), menopausal status, recent postmenopausal hormone use at blood collection (within 3 months, except for the myocardial infarction case-control study), as well as other factors carefully chosen for each individual study. The current analysis was limited to healthy controls. We also included existing LTL data from a small random sample of women participating in a cognitive sub-study. LTL was measured using the quantitative PCR-based method. Exposure and covariate information are extracted from biennial questionnaires completed by the participants. Main results and the role of chance: We found a strong association between paternal age at birth and participant LTL (P = 1.6 × 10-5) that remained robust after controlling for indicators of early life SES. Maternal age at birth showed a weak inverse association with participant LTL after adjusting for age at blood collection and paternal age at birth (P = 0.01). We also noted a stronger association between paternal age at birth and participant LTL among premenopausal than among postmenopausal women (Pinteraction = 0.045). However, this observation may be due to chance as premenopausal women represented only 12.6% (N = 535) of the study population and LTL was not correlated with age at menopause, total or estrogen-only hormone therapy (HT) use suggesting that changes in in vivo estrogen exposure do not influence telomere length regulation.
Medical Anthropology Quarterly, September 2012, Pages 361-382
Even in a country with super-low fertility rates, at least one-quarter of all babies are unplanned. The finding puzzles policymakers. This article uses Italy's "curious case" as a jumping-off point to expose assumptions about rationality. It offers a model to dismantle the "conceit" of rationality, drawing on Max Weber's classic critique and Emily Martin's contemporary appraisal. It asks: (1) How do assumptions about rationality related to sexuality and reproduction manifest? (2) How do qualitative data challenge rationalist assumptions? and (3) How are cultural logics expressed and what do they reveal about the "problem" of low fertility? Methodologically, the article offers an innovative approach, juxtaposing ethnographic data derived from the author's fieldwork with startling findings from Italian researchers' multicity project. The analysis exposes the rationality trope as a technique of governance in a context in which policymakers yearn for social cohesion and population politics intensify around birthing, immigration, and aging.