Fertilized
Maternal Stress and Child Outcomes: Evidence from Siblings
Anna Aizer, Laura Stroud & Stephen Buka
NBER Working Paper, September 2012
Abstract:
We study how maternal stress affects offspring outcomes. We find that in-utero exposure to elevated levels of the stress hormone cortisol negatively affects offspring cognition, health and educational attainment. These findings are based on comparisons between siblings which limits variation to short-lived shocks and controls for unobserved differences between mothers that could bias estimates. Our results are consistent with recent experimental results in the neurobiological literature linking exogenous exposure to stress hormones in-utero with declines in offspring cognitive, behavioral and motor development. Moreover, we find that not only are mothers with low levels of human capital characterized by higher and more variable cortisol levels, but that the negative impact of elevated cortisol is greater for them. These results suggest that prenatal stress may play a role in the intergenerational persistence of poverty.
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His and Her Job: What Matters Most for Fertility Plans and Actual Childbearing?
Gayle Kaufman & Eva Bernhardt
Family Relations, October 2012, Pages 686-697
Abstract:
This study examines workplace culture and fertility plans and transitions in Sweden. This study goes beyond previous research in examining the effect of particular job characteristics as well as the influence of a partner's job characteristics on women's and men's birth plans and transitions. We use data from the 1999 and 2003 Swedish Young Adult Panel Study. Results indicate that men are more likely to intend to have a child if their partner's job makes it easy to take parental leave or work part-time. Women are more likely to intend to have a child if their partner's job pays well. In addition, men whose job pays well are more likely to have a child. This research suggests that family-friendly policies may enhance fertility indirectly through men's fertility decision making.
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Ernest Onyishi et al.
Evolution and Human Behavior, forthcoming
Abstract:
Previous research has demonstrated that having more children decreases marital satisfaction among parents. However, the universality of these findings is limited since the vast majority of the studies have been conducted in Western countries. In the present study, 374 people from the Igbo ethnic group (Nigeria) were assessed for levels of marital satisfaction and the number of children. In contrast to almost all previous findings, we found a positive relationship between the number of children and marital satisfaction among parents. Number of children was the strongest predictor of marital satisfaction even when compared to other variables like wealth and education. Our results suggest that the negative relationship between the number of children and marital satisfaction is not culturally universal and probably only characterizes developed, individualistic Western countries. We discuss our findings from a sociocultural and evolutionary perspective.
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The one-child policy: A macroeconomic analysis
Pei-Ju Liao
Journal of Development Economics, forthcoming
Abstract:
This paper studies the effects of China's one-child policy. Using a calibrated general-equilibrium model, a benchmark with a fertility constraint in place is compared to a counterfactual experiment without the fertility constraint. The results indicate that the implementation of the one-child policy promotes the accumulation of human capital and increases per capita output. In addition, the policy leads to different welfare effects across generations and skill groups. The initial generation would benefit from relaxing the one-child policy, but the following generations would be hurt. A redistribution effect between skilled and unskilled workers is also observed. These findings demonstrate that focusing solely on GDP per capita as a measure of economic well-being paints an incomplete picture of the welfare consequences of population policies.
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Fertility Regulation in an Economic Crisis
Christopher McKelvey, Duncan Thomas & Elizabeth Frankenberg
Economic Development and Cultural Change, October 2012, Pages 7-38
Abstract:
Substantial international aid is spent reducing the cost of contraception in developing countries as part of a larger effort to reduce global fertility and increase investment per child worldwide. The importance for fertility behaviors of keeping contraceptive prices low, however, remains unclear. Targeting of subsidies and insufficient price variation have hindered prior attempts to estimate the effect of monetary and nonmonetary contraceptive costs on fertility behavior. Using longitudinal survey data from the Indonesia Family Life Survey, we exploit dramatic variation in prices and incomes that was induced by the economic crisis in the late 1990s to pin down the effect of contraceptive availability and costs as well as household resources on contraceptive use and method choice. The results are unambiguous: monetary costs of contraceptives and levels of family economic resources have a very small (and well-determined) impact on contraceptive use and choice of method.
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Relationship of Fertility with Intelligence and Education in Taiwan: A Brief Report
Hsin-Yi Chen et al.
Journal of Biosocial Science, forthcoming
Abstract:
This study estimates the effect of dysgenic trends in Taiwan by exploring the relationships among intelligence, education and fertility. Based on a representative adult sample, education and intelligence were negatively correlated with the number of children born. These correlations were stronger for females. The decline of genotypic intelligence was estimated as 0.82 to 1.33 IQ points per generation for the Taiwanese population.
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Parasite Stress Predicts Offspring Sex Ratio
Madhukar Shivajirao Dama
PLoS ONE, September 2012
Abstract:
In this study, I predict that the global variation of offspring sex ratio might be influenced in part by the level of parasite stress. From an energetic standpoint, higher gestational costs of producing a male offspring could decrease male births in a population with limited resources. This implies that, any factor that limits the parental resources could be expected to favor female offspring production. Human sex ratio at birth (SRB) is believed to be influenced by numerous socioeconomic, biological, and environmental factors. Here, I test a prediction that parasite stress, by virtue of its effects on the general health condition, may limit the parental investment ability and therefore could influence the SRB at the population level. The statistical analysis supports this prediction, and show that the level of parasite stress has a significant inverse relation with population SRB across the world. Further, this relation is many-folds stronger than the association of SRB with other factors, like; polygyny, fertility, latitude, and son-preference. Hence, I propose that condition affecting ability of parasites (but not adaptive significance) could be a likely causal basis for the striking variation of SRB across populations.
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Preventing Unintended Pregnancies by Providing No-Cost Contraception
Jeffrey Peipert et al.
Obstetrics & Gynecology, forthcoming
Objective: To promote the use of long-acting reversible contraceptive (LARC) methods (intrauterine devices [IUDs] and implants) and provide contraception at no cost to a large cohort of participants in an effort to reduce unintended pregnancies in our region.
Methods: We enrolled 9,256 adolescents and women at risk for unintended pregnancy into the Contraceptive CHOICE Project, a prospective cohort study of adolescents and women desiring reversible contraceptive methods. Participants were recruited from the two abortion facilities in the St. Louis region and through provider referral, advertisements, and word of mouth. Contraceptive counseling included all reversible methods but emphasized the superior effectiveness of LARC methods (IUDs and implants). All participants received the reversible contraceptive method of their choice at no cost. We analyzed abortion rates, the percentage of abortions that were repeat abortions, and teenage births.
Results: We observed a significant reduction in the percentage of abortions that were repeat abortions in the St. Louis region compared with Kansas City and nonmetropolitan Missouri (P<.001). Abortion rates in the CHOICE cohort were less than half the regional and national rates (P<.001). The rate of teenage birth within the CHOICE cohort was 6.3 per 1,000, compared with the U.S. rate of 34.3 per 1,000.
Conclusion: We noted a clinically and statistically significant reduction in abortion rates, repeat abortions, and teenage birth rates. Unintended pregnancies may be reduced by providing no-cost contraception and promoting the most effective contraceptive methods.
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Schools, Their Spatial Distribution and Characteristics, and Fertility Limitation
Sarah Brauner-Otto
Rural Sociology, September 2012, Pages 321-354
Abstract:
This article investigates the complex relationship between various dimensions of women's educational context and their contraceptive use later in life. Using data from rural Nepal on all the schools that ever existed in one community, I create geographically weighted measures of school characteristics - specifically teacher and student characteristics - that capture exposure to the complete array of schools and investigate the direct relationship between these dimensions of school characteristics and contraceptive use. These analyses provide new information on the broader issue of how social context influences the adoption of innovative behaviors by exploring the wide-reaching effects of school characteristics on individuals. Findings show that the gender of teachers, the gender of other students, and the level of teacher education are all related to women's use of contraception; that increased exposure to these school characteristics throughout the study area, but not necessarily at the closest school, is related to higher rates of contraceptive use; and that school characteristics early in the life course can have long-term consequences for individual behavior.
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Cohabiting Men's Preferences for and Roles in Determining the Outcomes of Unexpected Pregnancies
Amanda Miller
Sociological Forum, September 2012, Pages 708-731
Abstract:
Growing numbers of men are fathering children within cohabiting unions. However, we know little about their desires for and preferred roles in making fertility decisions. To address this gap, I use data from 61 in-depth interviews with working- and middle-class cohabiting men to examine their stated preferences should their partners experience an unplanned pregnancy. For some men, the decision appears to be a relatively stable personal or political one, but most draw on their current relationships and/or financial or maturational situations when noting their desires. A subsample of 22 men from this group who have experienced pregnancies is used to explore men's actual roles in negotiating whether a conception was terminated or carried to term. Despite the fact that most men would like to have input into decisions to abort or carry a pregnancy to term, the majority were not actually involved in making decisions with their partners (especially the decision to abort) when pregnancies occurred. Results are interpreted in light of social class differences in family formation processes.
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Birth outcomes after induced abortion: A nationwide register-based study of first births in Finland
R. Klemetti et al.
Human Reproduction, forthcoming
Study question: Is the perinatal health of first-born children affected by the mother's previous induced abortion(s) (IAs)?
Summary answer: Prior IAs, particularly repeat IAs, are correlated with an increased risk of some health problems at first birth; even in a country with good health care quality.
What is known already: A positive association between IA and risk of preterm birth or a dose-response effect has been found in some previous studies. Limited information and conflicting results on other infant outcomes are available.
Study design, size and duration: Nationwide register-based study including 300 858 first-time mothers during 1996-2008 in Finland.
Participants/materials, setting and methods: All the first-time mothers with a singleton birth (obtained from the Medical Birth Register) in the period 1996-2008 (n = 300 858) were linked to the Abortion Register for the period 1983-2008.
Main results and the role of chance: Of the first-time mothers, 10.3% (n = 31 083) had one, 1.5% had two and 0.3% had three or more IAs. Most IAs were surgical (88%) performed before 12 weeks (91%) and carried out for social reasons (97%). After adjustment, perinatal deaths and very preterm birth (<28 gestational week) suggested worse outcomes after IA. Increased odds for very preterm birth were seen in all the subgroups and exhibited a dose-response relationship: 1.19 [95% confidence interval (CI) 0.98-1.44] after one IA, 1.69 (1.14-2.51) after two and 2.78 (1.48-5.24) after three IAs. Increased odds for preterm birth (<37 weeks) and low birthweight (<2500 g and <1500 g) were seen only among mothers with three or more IAs: 1.35 (1.07-1.71), 1.43 (1.12-1.84) and 2.25 (1.43-3.52), respectively.
Limitations, reasons for caution: Observational studies like ours, however large and well-controlled, will not prove causality.
Wider implications of the findings: In terms of public health and practical implications, health education should contain information of the potential health hazards of repeat IAs, including very preterm birth and low birthweight in subsequent pregnancies. Health care professionals should be informed about the potential risks of repeat IAs on infant outcomes in subsequent pregnancy.
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Has Divorce Become a Pro-Natal Force in Europe at the Turn of the 21st Century?
Jan Van Bavel, Mieke Jansen & Belinda Wijckmans
Population Research and Policy Review, October 2012, Pages 751-775
Abstract:
Since the 1990s, the correlation between divorce and total fertility has turned positive on the country level in Europe. This paper investigates whether this positive association also holds on the individual level. To this end, it uses micro-level data from the third round of the European Social Survey about 23 countries. We introduce location-scale models to analyze both the average number of children and the dispersion around this number. Particular attention goes to the role played by repartnering. We find that a past divorce experience is generally negatively associated with the number of children ever born for both men and women, even for people who are in a new post-divorce union. So, contrary to what is suggested by aggregate level correlations, divorce has not become a pro-natal force in Europe. The only exception may be remarried men, who are somewhat more likely to have three or more children in our sample. Whereas the difference in average number of children born between divorced and never divorced people is small, divorce is associated with much greater heterogeneity in childbearing.
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Lisa Mcallister et al.
American Journal of Human Biology, forthcoming
Objectives: We develop and test a conceptual model of factors influencing women's ideal family size (IFS) in a natural fertility population, the Tsimane of Bolivia. The model posits affects of socioecology, reproductive history, maternal condition, and men's IFS. We test three hypotheses for why women may exceed their IFS despite experiencing socioeconomic development: (H1) limited autonomy; (H2) improved maternal condition; and (H3) low returns on investments in embodied capital.
Methods: Women's reproductive histories and prospective fertility data were collected from 2002 to 2008 (n = 305 women). Semistructured interviews were conducted with Tsimane women to study the perceived value of parental investment (n = 76). Multiple regression, t-tests, and analysis of variance (ANOVA) are used to test model predictions.
Results: Women's IFS is predicted by their socioecology, reproductive history, maternal condition, and husband's IFS. Hypotheses 2 and 3 are supported. Couples residing near town have smaller IFS (women = 3.75 ± 1.64; men = 3.87 ± 2.64) and less variance in IFS. However, the degree fertility exceeds IFS is inversely correlated with distance to town (Partial r = -0.189, df = 156, P = 0.018). Women living near town have greater maternal condition but 64% value traditional skills over formal schooling and 88% believe living in town is unfeasible.
Conclusions: While reduced IFS is evident with socioeconomic development, fertility decline may not immediately follow. When perceived benefits of investment in novel forms of embodied capital are low, and somatic wealth and large kin networks persist as important components of fitness, fertility may remain high and increase if maternal condition improves.
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Martin Kolk & Sebastian Schnettler
Journal of Biosocial Science, forthcoming
Abstract:
Based on evolutionary reasoning, Trivers & Willard (1973) predicted status-biased sex composition and parental investment with son-preferencing effects in higher, and daughter-preferencing effects in lower status groups. Previous research shows mixed results. This study uses event-history methods and Swedish register data to study one possible mechanism in isolation: do parents in different status groups vary in their proclivities to continue fertility based on the sex composition of previous offspring? The results show no support for the Trivers-Willard hypothesis on a wide range of different status indicators. Future research on the stated hypothesis should focus on physiological rather than behavioural mechanisms.
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Dietary patterns and semen quality in young men
Audrey Gaskins et al.
Human Reproduction, October 2012, Pages 2899-2907
Study question: Are different dietary patterns associated with semen parameters in young men?
Study answer: The consumption of a Prudent dietary pattern was significantly associated with higher progressive sperm motility and unrelated to sperm concentration and morphology. The consumption of a Western dietary pattern was unrelated to conventional semen quality parameters.
What is known already: Over the past decades there has been evidence of a concomitant decline in sperm and diet quality. Yet whether diet composition influences semen quality remains largely unexplored.
Study design, size, duration: The Rochester Young Men's Study (n= 188) was a cross-sectional study conducted between 2009 and 2010 at the University of Rochester.
Participants, setting, methods: Men aged 18-22 years were included in this analysis. Diet was assessed via food frequency questionnaire and dietary patterns were identified by factor analysis. Linear regression was used to analyze the relation between diet patterns and conventional semen quality parameters (sperm concentration, progressive motility and morphology) adjusting for abstinence time, multivitamin use, race, smoking status, BMI, recruitment period, moderate-to-intense exercise and total calorie intake.
Results: Two dietary patterns were identified by factor analysis. The ‘Western' pattern was characterized by high intake of red and processed meat, refined grains, pizza, snacks, high-energy drinks and sweets. The ‘Prudent' pattern was characterized by high intake of fish, chicken, fruit, vegetables, legumes and whole grains. The Prudent pattern was positively associated with percent progressively motile sperm in multivariate models (P-trend = 0.04). Men in the highest quartile of the Prudent diet had 11.3% (95% CI 1.3, 21.3) higher % progressively motile sperm compared with men in the lowest quartile. The Prudent pattern was unrelated to sperm concentration and morphology. The Western pattern was not associated with any semen parameter.
Limitations: This was a cross-sectional and observational study, which limited our ability to determine causality of diet on semen quality parameters.
Wider implications of the findings: Our findings support the suggestion that a diet rich in fruits, vegetables, chicken, fish and whole grains may be an inexpensive and safe way to improve at least one measure of semen quality.
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Paternal Age and Risk of Autism in an Ethnically Diverse, Non-Industrialized Setting: Aruba
Ingrid van Balkom et al.
PLoS ONE, September 2012
Objective: The aim of this study was to examine paternal age in relation to risk of autism spectrum disorders (ASDs) in a setting other than the industrialized west.
Design: A case-control study of Aruban-born children (1990-2003). Cases (N = 95) were identified at the Child and Adolescent Psychiatry Clinic, the only such clinic in Aruba; gender and age matched controls (N = 347) were gathered from public health records. Parental age was defined categorically (≤29, 30-39, 40-49, ≥50y). The analysis was made, using conditional logistic regression.
Results: Advanced paternal age was associated with increased risk of ASDs in offspring. In comparison to the youngest paternal age group (≤29y), risk of autism increased 2.18 times for children born from fathers in their thirties, 2.71 times for fathers in their forties, and 3.22 thereafter.
Conclusion: This study, part of the first epidemiologic study of autism in the Caribbean, contributes additional evidence, from a distinctive sociocultural setting, of the risk of ASD associated with increased paternal age.
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Johannes Johow & Eckart Voland
Human Nature, September 2012, Pages 341-359
Abstract:
Based on historical data pertaining to the Krummhörn population (eighteenth and nineteenth centuries, Germany), we compared reproductive histories of mothers according to whether the maternal grandmother (MGM) or the paternal grandmother (PGM) or neither of them was resident in the parents' parish at the time of the mother's first birth. In contrast to effects of PGMs, we discovered conditional differences in the MGM's effects between landless people and wealthier, commercial farmers. Our data indicate that the presence of the MGM only lowers the woman's age at marriage (AAM) and her age at the birth of her first child (AFB) in the case of landless families. However, among commercial farmers, who can generally be characterized by a lower AAM and AFB, we found opposite tendencies for the MGM's effect leading to a relatively small delay in AAM and AFB. Moreover, we also analyzed differences in the completed fertility (i.e., children ever born: CEB). Results indicate that landless families in general do have fewer CEB compared with commercial farmers except for those families in which the MGM has been present. Emphasizing that the adaptiveness of investment decisions should depend on the interaction of genetic, lineage-specific (intrinsic) and ecologically imposed (extrinsic) constraints, we conclude that kin strategies consequently address different fitness components under different conditions.