Fertility and Childbearing
Socioeconomic status, education, and reproduction in modern women: An evolutionary perspective
Susanne Huber, Fred Bookstein & Martin Fieder
American Journal of Human Biology, forthcoming
Abstract:
Although associations between status or resources and reproduction are positive in premodern societies and also in men in modern societies, in modern women the associations are typically negative. We investigated how the association between socioeconomic status and reproductive output varies with the source of status and resources, the woman's education, and her age at reproductive onset (proxied by age at marriage). By using a large sample of US women, we examined the association between a woman's reproductive output and her own and her husband's income and education. Education, income, and age at marriage are negatively associated with a woman's number of children and increase her chances of childlessness. Among the most highly educated two-thirds of the sample of women, husband's income predicts the number of children. The association between a woman's number of children and her husband's income turns from positive to negative when her education and age at marriage is low (even though her mean offspring number rises at the same time). The association between a woman's own income and her number of children is negative, regardless of education. Rather than maximizing the offspring number, these modern women seem to adjust investment in children based on their family size and resource availability. Striving for resources seems to be part of a modern female reproductive strategy - but, owing to costs of resource acquisition, especially higher education, it may lead to lower birthrates: a possible evolutionary explanation of the demographic transition, and a complement to the human capital theory of net reproductive output.
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Work-Family Conflict and Fertility Intentions: Does Gender Matter?
Karina Shreffler, Amy Pirretti & Robert Drago
Journal of Family and Economic Issues, June 2010, Pages 228-240
Abstract:
Fertility among employed women remains far below their desired preferences. Although research has shown that fertility intentions significantly predict subsequent behavior, little is known about the factors that contribute to intentions. We assess the impacts of perceived self and partner work-to-family and family-to-work conflict on the fertility intentions of both women and men. Using a national probability sample of men and women in dual-earner families (N = 630), we find that men's perceptions of their wives' work-family conflict significantly predict men's fertility intentions, even though men's own work-family conflict does not. Neither women's own work-family conflict nor their perceptions of their husbands' work-family conflict predicts women's fertility intentions.
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Are Children Really Inferior Goods? Evidence from Displacement-Driven Income Shocks
Jason Lindo
Journal of Human Resources, March 2010, Pages 301-327
Abstract:
This paper explores the causal link between income and fertility by analyzing women's fertility response to the large and permanent income shock generated by a husband's job displacement. I find that the shock reduces total fertility, suggesting that the causal effect of income on fertility is positive. A model that incorporates the time cost of children and assortative matching of spouses can simultaneously explain this result and the negative cross-sectional relationship. I also find that a husband's displacement accelerates childbearing, which is consistent with lifecycle models of fertility in which the incentive to delay is driven by expected earnings growth.
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The Importance of Being Wanted
Quy-Toan Do Tung Duc Phung
American Economic Journal: Applied Economics, forthcoming
Abstract:
We identify birth wantedness as a source of better child outcomes. In Vietnam, the year of birth is widely believed to determine success. As a result, cohorts born in auspicious years are 12 percent larger. Comparing siblings with one another, those of auspicious cohorts are found to have 2 extra months of schooling. The Vietnamese horoscope being gender-specific, this difference will be shown to be driven by birth planning; children born in auspicious years are more likely to have been planned, thus benefitting from a more favorable growth environment.
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Wage Work for Women: The Menstrual Cycle and the Power of Water
Yasheng Maimaiti & Stanley Siebert
University of Birmingham Working Paper, February 2010
Abstract:
We hypothesise that women's participation in wage (off-farm) work is reduced when their greater water needs due to the menstrual cycle are not met because their household has poor access to water. For testing, we use the data from rural villages in China. Controlling for village fixed effects, poor access to water is found to decrease the probability of wage work participation of affected (pre-menopause) women by about 10 percentage points, a large effect. As expected, there is no adverse causal impact of poor household access to water for women post-menopause, or for men, ceteris paribus.
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Adult temperament and childbearing over the life course
Markus Jokela, Taina Hintsa, Mirka Hintsanen & Liisa Keltikangas-Järvinen
European Journal of Personality, March 2010, Pages 151-166
Abstract:
Emerging evidence suggests that temperament may predict childbearing. We examined the association between four temperament traits (novelty seeking, harm avoidance, reward dependence and persistence of the Temperament and Character Inventory) and childbearing over the life course in the population-based Cardiovascular Risk in Young Finns study (n = 1535; 985 women, 550 men). Temperament was assessed when the participants were aged 20-35 and fertility history from adolescence to adulthood was reported by the participants at age 30-45. Discrete-time survival analysis modelling indicated that high childbearing probability was predicted by low novelty seeking (standardized OR = 0.92; 95% confidence interval 0.88-0.97), low harm avoidance (OR = 0.90; 0.85-0.95), high reward dependence (OR = 1.09; 1.03-1.15) and low persistence (OR = 0.91; 0.87-0.96) with no sex differences or quadratic effects. These associations grew stronger with increase in numbers of children. The findings were substantially the same in a completely prospective analysis. Adjusting for education did not influence the associations. Despite its negative association with overall childbearing, high novelty seeking increased the probability of having children in participants who were not living with a partner (OR = 1.29; 1.12-1.49). These data provide novel evidence for the role of temperament in influencing childbearing, and suggest possible weak natural selection of temperament traits in contemporary humans.
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Female-to-Male Breeding Ratio in Modern Humans - an Analysis Based on Historical Recombinations
Damian Labuda, Jean-François Lefebvre, Philippe Nadeau & Marie-Hélène Roy-Gagnon
American Journal of Human Genetics, 12 March 2010, Pages 353-363
Abstract:
Was the past genetic contribution of women and men to the current human population equal? Was polygyny (excess of breeding women) present among hominid lineages? We addressed these questions by measuring the ratio of population recombination rates between the X chromosome and the autosomes, ρX/ρA. The X chromosome recombines only in female meiosis, whereas autosomes undergo crossovers in both sexes; thus, ρX/ρA reflects the female-to-male breeding ratio, β. We estimated β from ρX/ρA inferred from genomic diversity data and calibrated with recombination rates derived from pedigree data. For the HapMap populations, we obtained β of 1.4 in the Yoruba from West Africa, 1.3 in Europeans, and 1.1 in East Asian samples. These values are consistent with a high prevalence of monogamy and limited polygyny in human populations. More mutations occur during male meiosis as compared to female meiosis at the rate ratio referred to as α. We show that at α ≠ 1, the divergence rates and genetic diversities of the X chromosome relative to the autosomes are complex functions of both α and β, making their independent estimation difficult. Because our estimator of β does not require any knowledge of the mutation rates, our approach should allow us to dissociate the effects of α and β on the genetic diversity and divergence rate ratios of the sex chromosomes to the autosomes.
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Missing Women: Age and Disease
Siwan Anderson & Debraj Ray
Review of Economic Studies, forthcoming
Abstract:
Relative to developed countries and some parts of the developing world, most notably sub-Saharan Africa, there are far less women than men in India and China. It has been argued that as many as a hundred million women could be missing. The possibility of gender bias at birth and the mistreatment of young girls are widely regarded as key explanations. We provide a decomposition of these missing women by age and cause of death. While we do not dispute the existence of severe gender bias at young ages, our computations yield some striking new findings: (1) The vast majority of missing women in India and a significant proportion of those in China are of adult age; (2) As a proportion of the total female population, the number of missing women is largest in sub-Saharan Africa, and the absolute numbers are comparable to those for India and China; and (3) Almost all the missing women stem from disease-by-disease comparisons and not from the changing composition of disease, as described by the epidemiological transition. Finally, using historical data, we argue that a comparable proportion of women was missing at the start of the 20th century in the United States, just as they are in India, China, and sub-Saharan Africa today.
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State Abortion Policy and the Long-Term Impact of Parental Involvement Laws
Marshall Medoff
Politics & Policy, April 2010, Pages 193-221
Abstract:
This paper presents empirical evidence that the enactment of parental involvement laws by states is a major reason for the steady decline in the incidence of abortion that has occurred in the United States since 1981. Parental involvement laws reduced the likelihood of teen minor females (under 18 years of age) having unwanted pregnancies by altering their frequency of unprotected sexual activity or contraceptive use. This change in teen minors' pregnancy avoidance behavior is found to be perpetuated over adult women's childbearing span of 18-44 years of age. Parental involvement laws are estimated to account for approximately one-third of the decline in the abortion rates of adult women of childbearing age over the period 1982-2000. The empirical results remain robust even after controlling for outliers, interstate migration, regional effects, and the presence of a waiting period.
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"Three thousand five hundred, 20- to 24-year-old women from Tromsø and Hamar in Norway were offered free hormonal contraception for a year. The result was that the abortion rate in the trial cities was halved." [Science Daily]
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Teen Fertility in Transition: Recent and Historic Trends in the United States
John Santelli & Andrea Melnikas
Annual Review of Public Health, 2010, Pages 371-383
Abstract:
After considerable declines in teen birth and pregnancy rates between 1991 and 2005, teen birth rates rose unexpectedly in 2006 and 2007. To understand these recent trends, we examined historical changes in fertility, trends in sexual behaviors, social forces, and public policies that may influence teen fertility. Although social forces such as poverty are critical in shaping adolescent reproductive choices, these do not explain rapid change in teen pregnancy risk since 1991. These recent changes, including increases in teen births since 2005, follow closely changes in teen contraceptive use. Likewise, contraceptive use is critical in explaining differences between U.S. and European fertility patterns. Public policies related to HIV prevention and sexuality education may have played a critical role in influencing teen pregnancy risk.
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Character as a Predictor of Reproductive Health Outcomes for Youth: A Systematic Review
Lawrence Duane House, Trisha Mueller, Belinda Reininger, Kathryn Brown & Christine Markham
Journal of Adolescent Health, March 2010, Pages S59-S74
Abstract:
To review research examining the influence of character on adolescent sexual and reproductive health (ASRH). We defined character as comprising two positive youth development constructs: prosocial norms and spirituality. We conducted a systematic review of behavioral research published from 1985 through 2007 that examined the association between two character constructs (prosocial norms and spirituality) and ASRH outcomes. We coded results as showing a protective association, risk association, or no association, and as longitudinal, or cross-sectional. We considered consistent associations from at least two longitudinal studies for a given outcome to be sufficient evidence for a protective or risk association. There is sufficient evidence to indicate that prosocial norms and spirituality can be protective factors for some ASRH outcomes including intention to have sex, early sex or ever having sex, contraceptive and condom use, frequency of sex, and pregnancy. The generalizability of findings by age, race/ethnicity, and gender was unclear. Findings suggest that some character sub-constructs are associated with a reduced likelihood of several adverse ASRH outcomes and with an increased likelihood of using contraceptives and intending to use condoms. Further research is needed to better understand mixed results and results showing some character sub-constructs, such as religious affiliation, to be associated with adverse ASRH outcomes.
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Jonathan Wells, Lewis Griffin & Philip Treleaven
American Journal of Human Biology, forthcoming
Abstract:
Both aging and reproduction have been shown to influence female body shape in industrialized populations, involving redistribution of fat from lower to upper body regions. However, the extent to which effects of parity vary by age and the extent to which age affects shape independent of parity remain unclear. We studied shape variability in relation to age and parity in a cross-sectional survey of 4,130 white British women, using three-dimensional photonic scanning. In women 40 years, bearing children was associated with increased abdominal and reduced thigh girths, independent of age and BMI. Very few such differences were statistically significant in women >40 years, suggesting the effects of parity on shape wash out over time. In nulliparous women, aging was associated with shape variability, independent of BMI, with a similar pattern of associations evident in women both 40 and >40 years. Our data support previous findings of covert maternal depletion in relation to parity, but show that this is merely a more pronounced component of a general strategic shift of fat from lower to upper body with age. These findings are consistent with a life-history model of female energy stores being allocated to competing reproduction and maintenance depots, with the optimal trade-off strategy changing with age and with that strategic shift accelerated by bearing children. This model is relevant to the grandmother hypothesis. The dual effects of age and parity on fat distribution substantially resolve by old age the profound sexual dimorphism in adiposity present at the start of adult life.
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Gijs Teklenburg et al.
PLoS ONE, April 2010, e10258
Background: Pregnancy is widely viewed as dependent upon an intimate dialogue, mediated by locally secreted factors between a developmentally competent embryo and a receptive endometrium. Reproductive success in humans is however limited, largely because of the high prevalence of chromosomally abnormal preimplantation embryos. Moreover, the transient period of endometrial receptivity in humans uniquely coincides with differentiation of endometrial stromal cells (ESCs) into highly specialized decidual cells, which in the absence of pregnancy invariably triggers menstruation. The role of cyclic decidualization of the endometrium in the implantation process and the nature of the decidual cytokines and growth factors that mediate the crosstalk with the embryo are unknown.
Methodology/Principal Findings: We employed a human co-culture model, consisting of decidualizing ESCs and single hatched blastocysts, to identify the soluble factors involved in implantation. Over the 3-day co-culture period, approximately 75% of embryos arrested whereas the remainder showed normal development. The levels of 14 implantation factors secreted by the stromal cells were determined by multiplex immunoassay. Surprisingly, the presence of a developing embryo had no significant effect on decidual secretions, apart from a modest reduction in IL-5 levels. In contrast, arresting embryos triggered a strong response, characterized by selective inhibition of IL-1β, -6, -10, -17, -18, eotaxin, and HB-EGF secretion. Co-cultures were repeated with undifferentiated ESCs but none of the secreted cytokines were affected by the presence of a developing or arresting embryo.
Conclusions: Human ESCs become biosensors of embryo quality upon differentiation into decidual cells. In view of the high incidence of gross chromosomal errors in human preimplantation embryos, cyclic decidualization followed by menstrual shedding may represent a mechanism of natural embryo selection that limits maternal investment in developmentally impaired pregnancies.