Fertile crescent
Birthing a Nation: The Effect of Fertility Control Access on the 19th Century Demographic Transition
Joanna Lahey
NBER Working Paper, January 2013
Abstract:
During the 19th century, the US birthrate fell by half. While previous economic literature has emphasized demand-side explanations for this decline - that rising land prices and literacy caused a decrease in demand for children - historians and others have emphasized changes in the supply of technologies to control fertility, including abortion and birth control. In this paper I exploit the introduction during the 19th century of state laws governing American women's access to abortion to measure the effect of changes in the supply of fertility technologies on the number of children born. I estimate an increase in the birthrate of 4 to 12% when abortion is restricted, which lies within the ranges of estimates found for the effect of fertility control supply restrictions on birthrates today. The importance of legal abortion in reducing 19th-century birthrates helps to account for a previously unexplained portion of the demographic transition. This paper posits that there has long been a demand, often unmet, for fertility control that should be considered in future demographic research as well as in policy formulation.
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Daniel Kruger, Jillian Clark & Sarah Vanas
American Journal of Human Biology, forthcoming
Objectives: Modern adverse birth outcomes may partially result from mechanisms evolved to evaluate environmental conditions and regulate maternal investment trade-offs. Male scarcity in a population is associated with a cluster of characteristics related to higher mating effort and lower paternal investment. We predicted that modern populations with male scarcity would have shorter gestational times and lower birth weights on average.
Methods: We compared US Centers for Disease Control and Prevention county-aggregated year 2000 birth records with US Decennial Census data. We combined these data in a path model with the degree of male scarcity and known socio-economic predictors of birth outcomes as exogenous predictors of prematurity and low birth weight, with single mother households as a proportion of families with children as a mediator (N = 450).
Results: Male scarcity was directly associated with higher rates of low birth weight. Male scarcity made significant indirect predictions of rates of prematurity and low birth weight, as mediated by the proportion of families headed by single mothers. Aggregate socio-economic status also indirectly predicted birth outcomes, as mediated by the proportion of families headed by single mothers, whereas the proportion African American retained both direct and indirect predictions of adverse birth outcomes.
Conclusions: Male scarcity influences life history tradeoffs, with consequences for important social and public health issues such as adverse birth outcomes.
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Sebastian Schnettler
PLoS ONE, February 2013
Abstract:
Based on evolutionary theory, Trivers & Willard (TW) predicted the existence of mechanisms that lead parents with high levels of resources to bias offspring sex composition to favor sons and parents with low levels of resources to favor daughters. This hypothesis has been tested in samples of wealthy individuals but with mixed results. Here, I argue that both sample selection due to a high number of missing cases and a lacking specification of the timing of wealth accumulation contribute to this equivocal pattern. This study improves on both issues: First, analyses are based on a data set of U.S. billionaires with near-complete information on the sex of offspring. Second, subgroups of billionaires are distinguished according to the timing when they acquired their wealth. Informed by recent insights on the timing of a potential TW effect in animal studies, I state two hypotheses. First, billionaires have a higher share of male offspring than the general population. Second, this effect is larger for heirs and heiresses who are wealthy at the time of conception of all of their children than for self-made billionaires who acquired their wealth during their adult lives, that is, after some or all of their children have already been conceived. Results do not support the first hypothesis for all subgroups of billionaires. But for males, results are weakly consistent with the second hypothesis: Heirs but not self-made billionaires have a higher share of male offspring than the U.S. population. Heiresses, on the other hand, have a much lower share of male offspring than the U.S. average. This hints to a possible interplay of at least two mechanisms affecting sex composition. Implications for future research that would allow disentangling the distinct mechanisms are discussed.
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Yuyu Chen, Hongbin Li & Lingsheng Meng
Journal of Human Resources, Winter 2013, Pages 36-70
Abstract:
How much of the increase in sex ratio (male to female) at birth since the early 1980s in China is attributed to increased prenatal sex selection? This question is addressed by exploiting the differential introduction of diagnostic ultrasound in the country during the 1980s, which significantly reduced the cost of prenatal sex selection. We find that the improved local access to ultrasound technology has resulted in a substantial increase in sex ratio at birth. Our estimates indicate that roughly 40 to 50 percent of the increase in sex imbalance at birth can be explained by local access to ultrasound examinations.
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Intergenerational effects of in utero exposure to Ramadan in Tunisia
S.H. Alwasel et al.
American Journal of Human Biology, forthcoming
Objectives: We have reported that changes in the lifestyle of pregnant women during Ramadan affect more than one generation. In a series of newborn babies in Saudi Arabia, those whose mothers had been in utero during Ramadan differed from those whose mothers had not been in utero during Ramadan. These were unexpected findings and require replication.
Methods: We examined body size at birth in 1,321 babies (682 boys and 639 girls) born in Gafsa, a small city in Tunisia.
Results: Babies whose mothers had been in utero during Ramadan were smaller and thinner, and had smaller placentas, than those whose mothers had not been in utero during Ramadan. After adjustment for sex, the babies were 93 g lighter (95% confidence interval, 32-153, P=0.003) than those whose mother had not been in utero during Ramadan, their mean ponderal index was 0.52 kg/m3 lower (0.24-0.79, P<0.001) and their placental weight was 21 g lower (5-37, P=0.01). The findings did not differ by trimester of maternal exposure to Ramadan. They were similar in boys and girls and in primiparous and multiparous mothers
Conclusion: This study provides further evidence that changes in lifestyle during Ramadan have intergenerational effects.
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Jeffrey Winking et al.
Proceedings of the Royal Society: Biological Sciences, 7 April 2013
Abstract:
The polygyny-fertility hypothesis states that polygyny is associated with reduced fertility for women and is supported by a large body of literature. This finding is important, because theoretical models of polygyny often differentiate systems based on the degree to which women are forced or willingly choose to enter polygynous marriages. The fact that polygyny tends to be associated with reduced fertility has been presented as evidence that polygyny is often less favourable for women, and that women must, therefore, be pressured into accepting such arrangements. Previous studies, however, have been hampered by the non-random assignment of women into monogamous and polygynous unions (i.e. self-selection), as differences between these groups of women might explain some of the effects. Furthermore, the vast majority of such studies focus on sub-Saharan populations. We address these problems in our analysis of women's fertility in polygynous marriages among the Tsimane of Bolivia. We offer a more robust method for assessing the impact of polygynous marriage on reproductive outcomes by testing for intra-individual fertility effects among first wives as they transition from monogamous to polygynous marriage. We report a significant link between polygyny and reduced fertility when including all cases of polygyny; however, this association disappears when testing only for intra-individual effects.
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DHA supplementation and pregnancy outcomes
Susan Carlson et al.
American Journal of Clinical Nutrition, forthcoming
Background: Observational studies associate higher intakes of n-3 (omega-3) long-chain PUFAs (LCPUFAs) during pregnancy with higher gestation duration and birth size. The results of randomized supplementation trials using various n-3 LCPUFA sources and amounts are mixed.
Objective: We tested the hypothesis that 600 mg/d of the n-3 LCPUFA DHA can increase maternal and newborn DHA status, gestation duration, birth weight, and length. Safety was assessed.
Design: This phase III, double-blind, randomized controlled trial was conducted between January 2006 and October 2011. Women (n = 350) consumed capsules (placebo, DHA) from <20 wk of gestation to birth. Blood (enrollment, birth, and cord) was analyzed for red blood cell (RBC) phospholipid DHA. The statistical analysis was intent-to-treat.
Results: Most of the capsules were consumed (76% placebo; 78% DHA); the mean DHA intake for the treated group was 469 mg/d. In comparison with placebo, DHA supplementation resulted in higher maternal and cord RBC-phospholipid-DHA (2.6%; P < 0.001), longer gestation duration (2.9 d; P = 0.041), and greater birth weight (172 g; P = 0.004), length (0.7 cm; P = 0.022), and head circumference (0.5 cm; P = 0.012). In addition, the DHA group had fewer infants born at <34 wk of gestation (P = 0.025) and shorter hospital stays for infants born preterm (40.8 compared with 8.9 d; P = 0.026) than did the placebo group. No safety concerns were identified.
Conclusions: A supplement of 600 mg DHA/d in the last half of gestation resulted in overall greater gestation duration and infant size. A reduction in early preterm and very-low birth weight could be important clinical and public health outcomes of DHA supplementation.
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High School Dropout and Teen Childbearing
Dave Marcotte
Economics of Education Review, forthcoming
Abstract:
Understanding the relationship between high school dropout and teen childbearing is complicated because both are affected by a variety of difficult to control factors. In this paper, I use panel data on aggregate dropout and fertility rates by age for all fifty states to develop insight by instrumenting for dropout using information on state policies on mandatory high school graduation exams. I then make use of these exit exam instruments in tandem with an instrument used previously in the literature to identify the impact of education on various outcomes: Compulsory schooling laws. Because these instruments operate at different margins, comparing effects provides insight into whether local average treatment effects are informative about average treatment effects relevant for a broader population than those complying with either instrument. The findings suggest that the elasticity of teen pregnancy with respect to high school dropout is 0.082 overall, with larger effects for black teens.
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C. Moreau et al.
Human Reproduction, March 2013, Pages 642-650
Study question: What is the predictive value of pregnancy intentions on contraceptive behaviours among women aged 18-19?
Summary answer: Women aged 18-19 have high levels of inconsistent use of contraception, which mostly occur at times when women strongly wish to avoid a pregnancy.
Study design, size, duration: In this study, data are drawn from a population-based survey of 992 women of ages 18-19 years in Michigan, who completed weekly journals assessing contraceptive use, pregnancy intentions and reproductive outcomes during 2.5 years of follow-up. The response rate was 86% for the baseline interview and 65% after 2.5 years of follow-up.
Participants/materials, setting, methods: We examined 15 446 pairs of journal entries. We used logistic regression with random effects to assess the predictive effect of women's desire to become pregnant and to avoid a pregnancy, measured each week, on consistency of use of contraception the following week.
Main results and the role of chance: Women reported inconsistent use of contraception in more than a quarter of weekly journals (28.3%). Consistent use of contraception increased from 22 to 78% as women s intentions to become pregnant decreased and increased from 23 to 78% as motivations to avoid pregnancy increased. The combination of scores of the pregnancy desire and avoidance scales shows indifferent or ambivalent pregnancy attitudes in 8.6% of weekly records. These women were more likely to report inconsistent contraceptive use compared with women who expressed anti-conception attitudes [OR = 2.8 (2.2-3.5)]. However, 23% of women who had unequivocal anti-conception feelings did not use contraception consistently, contributing to 72% of the weeks of inconsistent use in our population.
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Legal Abortion Levels and Trends By Woman's Age at Termination
Gilda Sedgh et al.
Perspectives on Sexual and Reproductive Health, forthcoming
Context: Assessments of abortion levels and trends by women's age at termination can be used to monitor trends in unintended pregnancy by age and can inform relevant programs and policies.
Methods: Legal abortion incidence data were compiled from national statistical offices and nationally representative surveys of more than 40 countries where legal abortion is generally available. Age-specific abortion rates and percentage distributions of abortions by age were computed, and trends since 1996 and 2003 were examined. Subregional and regional estimates were developed for geographic areas where the majority of the population was represented by the data.
Results: The median year for the most recent estimates of abortions by woman's age was 2009. Adolescents accounted for a smaller share of abortions than their share of the population in the majority of eligible countries with data. In most countries, the highest age-specific abortion rates and proportions of abortions were among women aged 20-29. Since 1996, adolescent abortion rates have increased the most in Belgium, the Netherlands and Scotland (22-42%), and have decreased the most in Estonia, Hungary, Iceland, Slovakia and Slovenia (40-55%). The proportion of abortions obtained by adolescents was higher in North America (18%) than in Europe overall (11%), although the proportion in Northern Europe (18%) was the same as that in North America.
Conclusions: Higher abortion rates in particular age-groups probably reflect higher-than-average levels of unmet need for contraception or difficulty using methods consistently and effectively, and a stronger desire to avoid childbearing. Each of the patterns observed has implications for service and information needs within countries.
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Does women's education affect fertility? Evidence from pre-demographic transition Prussia
Sascha Becker, Francesco Cinnirella & Ludger Woessmann
European Review of Economic History, Fenruary 2013, Pages 24-44
Abstract:
While women's employment opportunities, relative wages, and the child quantity-quality trade-off have been studied as factors underlying historical fertility limitation, the role of women's education has received little attention. We combine Prussian county data from three censuses - 1816, 1849, and 1867 - to estimate the relationship between women's education and their fertility before the demographic transition. Despite controlling for several demand and supply factors, we find a negative residual effect of women's education on fertility. Instrumental-variable estimates using educational variation deriving from landownership concentration, as well as panel estimates controlling for fixed effects of counties, suggest that the effect of women's education on fertility is causal.
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Discrimination Begins in the Womb: Evidence of Sex-Selective Prenatal Investments
Prashant Bharadwaj & Leah Lakdawala
Journal of Human Resources, Winter 2013, Pages 71-113
Abstract:
This paper investigates whether boys receive preferential prenatal treatment in a setting where son preference is present. Using micro health data from India, we highlight sex-selective prenatal investments as a new channel via which parents practice discriminatory behavior. We find that mothers visit antenatal clinics and receive tetanus shots more frequently when pregnant with a boy. Preferential prenatal treatment of males is greater in regions known to have strong son preference and among women whose previous children are female. We address other mechanisms such as selective recall, medical complications that might cause male fetuses to receive greater prenatal care in general, son preference-based fertility stopping rules and biases due to sex-selective abortions. Our calculations suggest that sex-selective prenatal care in maternal tetanus vaccination explains between 2.6-7.2 percent of excess female neonatal mortality in India.
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Personality is differentially associated with planned and non-planned pregnancies
Venla Berg et al.
Journal of Research in Personality, forthcoming
Abstract:
Recent studies have linked personality with family formation and having children. We studied whether personality traits are differentially associated with planned versus non-planned pregnancies. The participants were 8,336 men and women from the 1958 British birth cohort study, with personality assessed in adulthood using the Five Factor Model. Planned pregnancies were more likely in women with high agreeableness and low openness to experience, and in men with high extraversion, high emotional stability, high conscientiousness, and low openness to experience. Non-planned pregnancies were more likely in women with high extraversion, low emotional stability, and low conscientiousness, and in men with high extraversion and low agreeableness. These results indicate that personality is associated with fertility differences via different pathways of fertility planning.
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U. Shukla et al.
Human Reproduction, March 2013, Pages 676-682
Study question: Has the change in donor anonymity legislation in UK affected the recruitment of men wanting to be sperm donors and also affected the attitudes of the practitioners who provide donor sperm treatment?
Summary answer: We have performed fewer IUI and IVF treatments using donor sperm following the change in legislation in April 2005 than before. However, we have seen an overall increase in men wanting to donate their sperm, including a small increase in men from ethnic minorities.
Study design, size, duration: This was a retrospective descriptive study that looked at all men who approached the clinic between the years 2000 and 2010, i.e. 5 years either side of the change in legislation (April 2005). Overall, we had 24 men wanting to be donors prior to the rule change and 65 men after the rule change. We also investigated the total number of all treatments with donor sperm, and this included a total of 1004 donor sperm treatments prior to the change in legislation and 403 donor sperm treatments after the change in legislation.
Participants, setting, methods: The study was set in an NHS IVF clinic in South East London. We compared the indicators of service provision, provider practices and donor attitudes, in the period between April 2000 and March 2005 (Group A) with those between April 2005 and March 2010 (Group B), i.e. 5 years either side of the change in legislation.
Main results: There were 875 IUI treatments and 129 IVF or ICSI treatments in Group A and 325 IUI and 78 IVF/ICSI treatments in Group B with the use of donor sperm, of which, 11.9% (119 out of 1004) in Group A and 39.5% (159 out of 403) in Group B were with donor sperm recruited by our unit. The clinical pregnancy rate per cycle of treatment in Group A was (86 out of 875) 9.8% for IUI and (27 out of 129) 20.9% for IVF/ICSI and in Group B (32/325) 9.8% and (28 out of 78) 35.9%, respectively. There was a sharp yearly fall in donor sperm treatments from 2004. Twenty-four men were screened in Group A, of which 18 (75.0%) were recruited for long-term storage and 12 (50%) were registered as donors with the HFEA when the sperm was used, whereas in Group B, 65 men were screened, 53 (82.0%) were recruited and 24 (36.92%) were registered as donors. Six (24.0%) men in Group A failed in screening because of poor semen analysis when compared with 9 (13.8%) men in Group B. The majority of post-recruitment dropouts were because of loss of follow-up or withdrawal of consent. More donors in Group A were white (92.0 versus 77.0%) and born in UK (92.0 versus 68.0%) when compared with those in Group B. Donors in Group B were more likely to be single (46.0 versus 4.0%) and to have informed their relevant partner of donation (71.0 versus 54.0%) when compared with those in Group A. 83.0% of donors in Group A were heterosexual when compared with 69.0% in Group B. The primary reason for donating in both groups of potential donors was ‘wanting to help' (46.0% ‘altruistic donors' in Group A versus 72.0% in Group B). Fewer donors in Group B (37%) had specific restrictions about the use of their sperm when compared with 46.0% in Group A.
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Jennifer Kane
Population Research and Policy Review, February 2013, Pages 47-80
Abstract:
Second demographic transition (SDT) theory posits that increased individualism and secularization have contributed to low fertility in Europe, but very little work has directly tested the salience of SDT theory to fertility trends in the US. Using longitudinal data from a nationally representative cohort of women who were followed throughout their reproductive years (National Longitudinal Survey of Youth 1979 cohort, NLSY79), this study examines the role of several key indicators of the SDT (secularization, egalitarianism, religious affiliation, and female participation in the labor market) on fertility behavior over time (1982-2006). Analyses employ Poisson estimation, logistic regression, and cross-lagged structural equation models to observe unidirectional and bidirectional relationships over the reproductive life course. Findings lend support to the relevance of SDT theory in the US but also provide evidence of "American bipolarity" which distinguishes the US from the European case. Furthermore, analyses document the reciprocal nature of these relationships over time which has implications for how we understand these associations at the individual-level.
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Tracy Weitz et al.
American Journal of Public Health, March 2013, Pages 454-461
Objectives: We examined the impact on patient safety if nurse practitioners (NPs), certified nurse midwives (CNMs), and physician assistants (PAs) were permitted to provide aspiration abortions in California.
Methods: In a prospective, observational study, we evaluated the outcomes of 11 487 early aspiration abortions completed by physicians (n = 5812) and newly trained NPs, CNMs, and PAs (n = 5675) from 4 Planned Parenthood affiliates and Kaiser Permanente of Northern California, by using a noninferiority design with a predetermined acceptable risk difference of 2%. All complications up to 4 weeks after the abortion were included.
Results: Of the 11 487 aspiration abortions analyzed, 1.3% (n = 152) resulted in a complication: 1.8% for NP-, CNM-, and PA-performed aspirations and 0.9% for physician-performed aspirations. The unadjusted risk difference for total complications between NP-CNM-PA and physician groups was 0.87 (95% confidence interval [CI] = 0.45, 1.29) and 0.83 (95% CI = 0.33, 1.33) in a propensity score-matched sample.
Conclusions: Abortion complications were clinically equivalent between newly trained NPs, CNMs, and PAs and physicians, supporting the adoption of policies to allow these providers to perform early aspirations to expand access to abortion care.
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Sperm counts may have declined in young university students in Southern Spain
Jaime Mendiola et al.
Andrology, forthcoming
Abstract:
Several studies have investigated temporal trends in semen quality in Northern Europe, but none has examined this question in Southern Europe. A prior study conducted in Almeria Province (Southern Spain) reported higher sperm count and concentration among Spanish young men recruited from 2001 to 2002 compared with young men from Northern Europe. The aim of this new study was to examine whether semen quality has changed among Spanish young men in the last decade. In this cross-sectional study, questionnaires and semen samples were collected from 215 healthy young university students from Murcia Region between 2010 and 2011. The 273 men from the Almeria study previously studied were included in a trend analysis of the two populations from Southern Spain. Descriptive statistics were calculated for the Murcia study population and these and semen variables for the Murcia and Almeria study populations were compared. Study methods and population characteristics were similar across the two studies. Therefore, we used multiple linear regression analyses on the combined population (controlling for study centre, age, ejaculation abstinence time, season, smoking, medication during the last 3 months, Body mass index (BMI), presence of varicocoele and prenatal exposure to tobacco) to look for a birth-cohort effect over the combined study period (2001-2011). Sperm concentration and total sperm count declined significantly with year of birth in the pooled analysis (β = -0.04 and β = -0.06, respectively, both p < 0.01). Sperm counts were significantly lower in Murcia study subjects than in the Almeria participants; sperm concentration median (5th-95th) = 44.0 (8.9-129) million/mL vs. 51.0 (5.0-206) million/mL; p < 0.01 and total sperm count = 121 (17.8-400) million vs. 149 (8.0-599) million; p < 0.01. Other semen variables did not differ significantly between the two studies. Our study suggests that total sperm count and sperm concentration may have declined in young Spanish men over the last decade.