Baby bump
Financial Incentives and Fertility
Alma Cohen, Rajeev Dehejia & Dmitri Romanov
Review of Economics and Statistics, March 2013, Pages 1-20
Abstract:
Using panel data on over 300,000 Israeli women from 1999 to 2005, we exploit variation in Israel's child subsidy to identify the impact of changes in the price of a marginal child on fertility. We find a positive, statistically significant, and economically meaningful price effect on overall fertility and, consistent with Becker (1960) and Becker and Tomes (1976), a small effect of income on fertility, which is negative at low and positive at high income levels. We also find a price effect on fertility among older women, suggesting that part of the overall effect is due to a reduction in total fertility.
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The Effect of Abortion Legalization on Childbearing by Unwed Teenagers in Future Cohorts
Serkan Ozbeklik
Economic Inquiry, forthcoming
Abstract:
This article examines the long-term impact of legalized abortion on childbearing by unwed teenagers in the United States. I find that the 1970 legalization of abortion in the repeal states led to about a 6% reduction in unwed childbearing rates for white women aged 15-20 who were born in these states immediately after abortion became legal. I find a larger long-term impact for African-American women of the same ages: a 7.5%-13% reduction in unwed childbearing. My estimates are smaller and not as precise for the effect of Roe v. Wade. This outcome is not surprising given that I am able to estimate only a potential lower bound of the effect on unwed childbearing rates. On the other hand, when I estimated a Difference-in-Difference regression for the non-repeal states assuming that there was no national trend that affected the childbearing behavior of the treatment age groups and their respective control age groups separately, I found that the true effect of Roe v. Wade on childbearing by unwed teenagers was about an 11% and 3% reductions for white and African-American teenagers, respectively.
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New Cohort Fertility Forecasts for the Developed World: Rises, Falls, and Reversals
Mikko Myrskylä, Joshua Goldstein & Yen-hsin Alice Cheng
Population and Development Review, March 2013, Pages 31-56
Abstract:
With period fertility having risen in many low-fertility countries, an important emerging question is whether cohort fertility trends are also reversing. We produce new estimates of cohort fertility for 37 developed countries using a new, simple method that avoids the underestimation typical of previous approaches. Consistent with the idea that timing changes were largely responsible for the last decades' low period fertility, we find that family size has remained considerably higher than the period rates of 1.5 in many "low-fertility" countries, averaging about 1.8 children. Our forecasts suggest that the long-term decline in cohort fertility is flattening or reversing in many world regions previously characterized by low fertility. We document the marked increase of cohort fertility in the English-speaking world and in Scandinavia; signs of an upward reversal in many low-fertility countries, including Japan and Germany; and continued declines in countries such as Taiwan and Portugal. We include in our forecasts estimates of statistical uncertainty and the possible effects of the recent economic recession.
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Reyn van Ewijk, Rebecca Painter & Tessa Roseboom
American Journal of Epidemiology, forthcoming
Abstract:
A growing body of evidence suggests that maternal diet during pregnancy can lead to permanent alterations to the physiology of the fetus. It is unknown whether intermittent maternal fasting during Ramadan has long-term associations with the offspring's body composition. By using data from the third wave of the Indonesian Family Life Survey (2000), we compared the body mass indices (weight (kg)/height (m)2) of Muslims who had been in utero during Ramadan with those of Muslims who had not been in utero during Ramadan. Adult Muslims who had been in utero during Ramadan were slightly thinner than Muslims who had not been in utero during Ramadan (adjusted adult body mass index: -0.32, 95% confidence interval: -0.57, -0.06). Those who were conceived during Ramadan also had smaller stature, being on average 0.80 cm shorter than those who were not exposed to Ramadan prenatally. Among non-Muslims, no such associations were found. This study suggests that exposure to Ramadan during pregnancy may have lasting consequences for adult body size of the offspring.
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Arindam Nandi & Anil Deolalikar
Journal of Development Economics, July 2013, Pages 216-228
Abstract:
Despite strong recent economic growth, gender inequality remains a major concern for India. This paper examines the effectiveness of a public policy geared towards the reduction of gender inequality. The national Pre-Conception and Pre-Natal Diagnostics Techniques (PNDT) Act of 1994, implemented in 1996, banned sex-selective abortions in India. Although demographers frequently mention the futility of the Act, we are among the first to evaluate the law using a treatment-effect analysis framework. Using village and town level longitudinal data from the 1991 and 2001 censuses, we find a significantly positive impact of the PNDT Act on female-to-male child sex ratio. Given the almost ubiquitous decline in the observed child sex ratio during this period, we argue that the law was successful in preventing any further worsening of the gender imbalance. We find that a possible absence of the law would have led to at least 106,000 fewer female children.
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Thomas Pollet, Kelly Cobey & Leander van der Meij
PLoS ONE, April 2013
Abstract:
Variation in testosterone (T) is thought to affect the allocation of effort between reproductive and parenting strategies. Here, using a large sample of elderly American men (n = 754) and women (n = 669) we examined the relationship between T and self-reported parenthood, as well as the relationship between T and number of reported children. Results supported previous findings from the literature, showing that fathers had lower T levels than men who report no children. Furthermore, we found that among fathers T levels were positively associated with the number of children a man reports close to the end of his lifespan. Results were maintained when controlling for a number of relevant factors such as time of T sampling, participant age, educational attainment, BMI, marital status and reported number of sex partners. In contrast, T was not associated with either motherhood or the number of children women had, suggesting that, at least in this sample, T does not influence the allocation of effort between reproductive and parenting strategies among women. Findings from this study contribute to the growing body of literature suggesting that, among men, pair bonding and paternal care are associated with lower T levels, while searching and acquiring sex partners is associated with higher T levels.
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Contraceptive use and unmet need for family planning in Iran
Mohammad Motlaq et al.
International Journal of Gynecology & Obstetrics, May 2013, Pages 157-161
Objective: To determine the prevalence of contraceptive use and unmet need for family planning in Iran and to explore the public-health implications.
Methods: A nationwide cross-sectional study was conducted by interviewing 2120 married women aged 15-49 years. The sample population was enrolled in 6 large Iranian cities (Tehran, Mashhad, Tabriz, Isfahan, Shiraz, and Ahvaz) and 2 small cities (Zahedan and Kerman) from September 22 to December 20, 2011.
Results: The overall contraceptive prevalence rate was 81.5% and the unmet need for any method of contraception was 2.6% (95% confidence interval, 2.0%-3.3%). Given the frequency of women who used traditional contraceptive methods (22.3%), the unmet need for modern methods was estimated as 17.4%. The main reasons given for unmet need for family planning were low perceived risk of pregnancy (41.8%) and family opposition (21.8%). Unwanted pregnancy was reported by 30.7% of the participants.
Conclusion: A high rate of unmet need for modern contraceptive methods might potentially lead to increased rates of unwanted pregnancies and induced abortions. Healthcare policymakers should, therefore, be warned against a sense of complacency that family planning in Iran does not need their support.
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Douglas Almond, Lena Edlund & Kevin Milligan
Population and Development Review, March 2013, Pages 75-95
Abstract:
Preference for sons over daughters, evident in China's and South Asia's male sex ratios, is commonly rationalized by poverty and the need for old-age support. In this article we study South and East Asian immigrants to Canada, a group for whom the economic imperative to select sons is largely absent. Analyzing the 2001 and 2006 censuses, 20 percent samples, we find clear evidence of extensive sex selection in favor of boys at higher parities among South and East Asian immigrants unless they are Christian or Muslim. The latter finding accords with the explicit prohibition against (female) infanticide - traditionally the main sex-selection method - in these religions. Our findings point to a strong cultural component to both the preference for sons and the willingness to resort to induced abortion based on sex.
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Autism Risk Across Generations: A Population-Based Study of Advancing Grandpaternal and Paternal Age
Emma Frans et al.
JAMA Psychiatry, forthcoming
Objective: To further expand knowledge about the association between paternal age and autism by studying the effect of grandfathers' age on childhood autism.
Design: Population-based, multigenerational, case-control study.
Setting: Nationwide multigeneration and patient registers in Sweden.
Participants: We conducted a study of individuals born in Sweden since 1932. Parental age at birth was obtained for more than 90% of the cohort. Grandparental age at the time of birth of the parent was obtained for a smaller subset (5936 cases and 30 923 controls).
Main Outcome and Measure: International Classification of Diseases diagnosis of childhood autism in the patient registry.
Results: A statistically significant monotonic association was found between advancing grandpaternal age at the time of birth of the parent and risk of autism in grandchildren. Men who had fathered a daughter when they were 50 years or older were 1.79 times (95% CI, 1.35-2.37; P < .001) more likely to have a grandchild with autism, and men who had fathered a son when they were 50 years or older were 1.67 times (95% CI, 1.35-2.37; P < .001) more likely to have a grandchild with autism, compared with men who had fathered children when they were 20 to 24 years old, after controlling for birth year and sex of the child, age of the spouse, family history of psychiatric disorders, highest family educational level, and residential county. A statistically significant monotonic association was also found between advancing paternal age and risk of autism in the offspring. Sensitivity analyses indicated that these findings were not the result of bias due to missing data on grandparental age.
Conclusions and Relevance: Advanced grandparental age was associated with increased risk of autism, suggesting that risk of autism could develop over generations. The results are consistent with mutations and/or epigenetic alterations associated with advancing paternal age.
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Tim Savage et al.
PLoS ONE, March 2013
Background: Maternal age at childbirth continues to increase worldwide. We aimed to assess whether increasing maternal age is associated with changes in childhood height, body composition, and metabolism.
Methods: 277 healthy pre-pubertal children, born 37-41 weeks gestation were studied. Assessments included: height and weight corrected for parental measurements, DEXA-derived body composition, fasting lipids, glucose, insulin, and hormonal profiles. Subjects were separated according to maternal age at childbirth: <30, 30-35, and >35 years.
Results: Our cohort consisted of 126 girls and 151 boys, aged 7.4±2.2 years (range 3-10); maternal age at childbirth was 33.3±4.7 years (range 19-44). Children of mothers aged >35 and 30-35 years at childbirth were taller than children of mothers aged <30 years by 0.26 (p = 0.002) and 0.23 (p = 0.042) SDS, respectively. There was a reduction in childhood BMISDS with increasing maternal age at childbirth, and children of mothers aged >35 years at childbirth were 0.61 SDS slimmer than those of mothers <30 years (p = 0.049). Children of mothers aged 30-35 (p = 0.022) and >35 (p = 0.036) years at childbirth had abdominal adiposity reduced by 10% and 13%, respectively, compared to those in the <30 group. Children of mothers aged 30-35 years at childbirth displayed a 19% increase in IGF-I concentrations compared to offspring in <30 group (p = 0.042). Conversely, IGF-II concentrations were lower among the children born to mothers aged 30-35 (6.5%; p = 0.004) and >35 (8.1%; p = 0.005) compared to those of mothers aged <30 years. Girls of mothers aged 30-35 years at childbirth also displayed improved HOMA-IR insulin sensitivity (p = 0.010) compared to girls born to mothers aged <30 years.
Conclusions: Increasing maternal age at childbirth is associated with a more favourable phenotype (taller stature and reduced abdominal fat) in their children, as well as improved insulin sensitivity in girls.
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Roland Pongou
Demography, April 2013, Pages 421-444
Abstract:
Infant mortality is higher in boys than girls in most parts of the world. This has been explained by sex differences in genetic and biological makeup, with boys being biologically weaker and more susceptible to diseases and premature death. At the same time, recent studies have found that numerous preconception or prenatal environmental factors affect the probability of a baby being conceived male or female. I propose that these environmental factors also explain sex differences in mortality. I contribute a new methodology of distinguishing between child biology and preconception environment by comparing male-female differences in mortality across opposite-sex twins, same-sex twins, and all twins. Using a large sample of twins from sub-Saharan Africa, I find that both preconception environment and child biology increase the mortality of male infants, but the effect of biology is substantially smaller than the literature suggests. I also estimate the interacting effects of biology with some intrauterine and external environmental factors, including birth order within a twin pair, social status, and climate. I find that a twin is more likely to be male if he is the firstborn, born to an educated mother, or born in certain climatic conditions. Male firstborns are more likely to survive than female firstborns, but only during the neonatal period. Finally, mortality is not affected by the interactions between biology and climate or between biology and social status.
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Geographical Mobility and Reproductive Choices of Italian Men
Raffaele Guetto & Nazareno Panichella
European Sociological Review, April 2013, Pages 302-315
Abstract:
In addition to women's increased educational attainment and institutional settings, also changed orientations toward family to achieve full life-satisfaction have been underlined to explain low fertility rates. Since Southern and Northern Italy differ for the institutional and economic setting, cultural orientations regarding the importance of family as well as fertility rates, also for Italy it seems reasonable to suppose that the latter are caused by both ‘structural' and ‘cultural' factors. We argue that South-to-North migrations could be an interpretative key of geographical differences in the timing and number of childbirths. In fact, migrants are socialized to different familiar behaviours, although they share with Northerners the same institutional and economic setting. We use data from the Italian Households Longitudinal Survey and apply event history models to Italian men's transition to parenthood. Our results show that North-South differences in the transition to the first child are largely explained by different levels and patterns of female labour market participation, while preferences could have a crucial impact in the transition to the second child, where migrants and Southerners are equally much faster than Northerners. We think that these results contribute to both the literature about fertility determinants and long-term consequences of migrations.
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The Effect of Fertility Reduction on Economic Growth
Quamrul Ashraf, David Weil & Joshua Wilde
Population and Development Review, March 2013, Pages 97-130
Abstract:
We assess quantitatively the effect of exogenous reductions in fertility on output per capita. Our simulation model allows for effects that run through schooling, the size and age structure of the population, capital accumulation, parental time input into childrearing, and crowding of fixed natural resources. The model is parameterized using a combination of microeconomic estimates and standard components of quantitative macroeconomic theory. We apply the model to examine the effect of a change in fertility from the UN medium-variant to the UN low-variant projection in Nigeria. For a base case set of parameters, we find that such a change would raise output per capita by 5.6 percent at a horizon of 20 years and by 11.9 percent at a horizon of 50 years. We conclude with a discussion of the quantitative significance of these results.
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Laure Dossus et al.
International Journal of Epidemiology, April 2013, Pages 590-600
Background: Age at menarche is an important determinant of hormonal-related neoplasia and other chronic diseases. Spatial and temporal variations in age at menarche have been observed in industrialised countries and several environmental factors were reported to have an influence.
Method: We examined geographical variations in self-reported age at menarche and explored the effects of both latitude and ultraviolet radiation (UVR) dose on the onset of menarche in 88 278 women from the French E3N cohort (aged 40-65 years at inclusion).
Results: The mean age at menarche was 12.8 years. After adjustment for potential confounders (birth cohort, prematurity, birth weight and length, father's income index, body silhouette in childhood, food deprivation during World War II, population of birthplace, number of siblings, breastfeeding exposure and indoor exposure to passive smoking during childhood), latitude and UVR dose (annual or spring/summer) in county of birth were significantly associated with age at menarche (Ptrend < 0.0001). Women born at lower latitudes or in regions with higher annual or spring/summer UVR dose had a 3- to 4-month earlier menarche than women born at higher latitudes or in regions with lower UVR. On a continuous scale, a 1° increment in latitude resulted in a 0.04-year older age at menarche [95% confidence interval (CI): 0.03, 0.05], whereas a 1-kJ/m2 increment in annual UVR dose resulted in a 0.42-year younger age at menarche (95% CI: -0.55, -0.29).
Conclusion: These data further suggest that light exposure in childhood may influence sexual maturation in women.
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The Impact of Malaria Eradication on Fertility
Adrienne Lucas
Economic Development and Cultural Change, April 2013, Pages 607-631
Abstract:
The malaria eradication campaign that started in Sri Lanka in the late 1940s virtually eliminated malaria transmission on the island. I use the preeradication differences in malaria endemicity within Sri Lanka to identify the effect of malaria eradication on fertility and child survival. Malaria eradication increased the number of live births through increasing age-specific fertility and causing an earlier first birth. The effect of malaria on the transition time to higher-order births is inconclusive. Malaria could directly or indirectly affect survival probabilities of live births. I exploit the particular epidemiology of malaria that causes more severe sequelae during an initial pregnancy. I find differential changes in survival probabilities by birth order that are most likely due to the direct in utero effects of malaria. The increase in population growth after malaria eradication reconciles the contradictory findings in the macroeconomic and microeconomic literatures: the increased productivity and education from malaria eradication will only appear in aggregate measures like GDP per capita after a delay because of the initial increase in the population size.
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Parent-Offspring Conflict and the Persistence of Pregnancy-Induced Hypertension in Modern Humans
Birgitte Hollegaard et al.
PLoS ONE, February 2013
Abstract:
Preeclampsia is a major cause of perinatal mortality and disease affecting 5-10% of all pregnancies worldwide, but its etiology remains poorly understood despite considerable research effort. Parent-offspring conflict theory suggests that such hypertensive disorders of pregnancy may have evolved through the ability of fetal genes to increase maternal blood pressure as this enhances general nutrient supply. However, such mechanisms for inducing hypertension in pregnancy would need to incur sufficient offspring health benefits to compensate for the obvious risks for maternal and fetal health towards the end of pregnancy in order to explain why these disorders have not been removed by natural selection in our hunter-gatherer ancestors. We analyzed >750,000 live births in the Danish National Patient Registry and all registered medical diagnoses for up to 30 years after birth. We show that offspring exposed to pregnancy-induced hypertension (PIH) in trimester 1 had significantly reduced overall later-life disease risks, but increased risks when PIH exposure started or developed as preeclampsia in later trimesters. Similar patterns were found for first-year mortality. These results suggest that early PIH leading to improved postpartum survival and health represents a balanced compromise between the reproductive interests of parents and offspring, whereas later onset of PIH may reflect an unbalanced parent-offspring conflict at the detriment of maternal and offspring health.
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Seminal and molecular evidence that sauna exposure affects human spermatogenesis
Andrea Garolla et al.
Human Reproduction, April 2013, Pages 877-885
Study question: What are the effects of continuous sauna exposure on seminal parameters, sperm chromatin, sperm apoptosis and expression of genes involved in heat stress and hypoxia?
Summary answer: Scrotal hyperthermia by exposure to sauna can induce a significant alteration of spermatogenesis.
Study design, size and duration: A longitudinal time-course study. Data from 10 subjects exposed to Finnish sauna were collected before sauna (T0), after3 months of sauna sessions (T1) and after 3 (T2) and 6 months (T3) from the end of sauna exposure.
Participants/materials, setting and methods: Ten normozoospermic volunteers underwent two sauna sessions per week for 3 months, at 80-90°C, each lasting 15 min. Sex hormones, sperm parameters, sperm chromatin structure, sperm apoptosis and expression of genes involved in heat stress and hypoxia were evaluated at the start, at the end of sauna exposure and after 3 and 6 months from sauna discontinuation. Student's t-test for paired data was used for statistical analysis.
Main results and the role of chance: At the end of sauna exposure, we found a strong impairment of sperm count and motility (P < 0.001), while no significant change in sex hormones was present. Decreases in the percentage of sperm with normal histone-protamine substitution (78.7 ± 4.5 versus 69.0 ± 4.1), chromatin condensation (70.7 ± 4.7 versus 63.6 ± 3.3) and mitochondrial function (76.8 ± 4.9 versus 54.0 ± 6.1) were also evident at T1, and strong parallel up-regulation of genes involved in response to heat stress and hypoxia was found. All these effects were completely reversed at T3.
Wider implications of the findings: Our data demonstrated for the first time that in normozoospermic subjects, sauna exposure induces a significant but reversible impairment of spermatogenesis, including alteration of sperm parameters, mitochondrial function and sperm DNA packaging. The large use of Finnish sauna in Nordic countries and its growing use in other parts of the world make it important to consider the impact of this lifestyle choice on men's fertility.