Vaccination, immunity, and the changing impact of COVID-19 on infant health.

In utero exposure to COVID-19 infection may lead to large intergenerational health effects. The impact of infection exposure has likely evolved since the onset of the pandemic as new variants emerge, immunity from prior infection increases, vaccines become available, and vaccine hesitancy persists, such that when infection is experienced is as important as whether it is experienced. We examine the changing impact of COVID-19 infection on preterm birth and the moderating role of vaccination. We offer the first plausibly causal estimate of the impact of maternal COVID-19 infection by using population data with no selectivity, universal information on maternal COVID-19 infection, and linked sibling data. We then assess change in this impact from 2020 to 2023 and evaluate the protective role of COVID-19 vaccination on infant health. We find a substantial adverse effect of prenatal COVID-19 infection on the probability of preterm birth. The impact was large during the first 2 y of the pandemic but had fully disappeared by 2022. The harmful impact of COVID-19 infection disappeared almost a year earlier in zip codes with high vaccination rates, suggesting that vaccines might have prevented thousands of preterm births. The findings highlight the need to monitor the changing consequences of emerging infectious diseases over time and the importance of mitigation strategies to reduce the burden of infection on vulnerable populations.

Menstrual irregularity as a biological limit to early pregnancy awareness.

US state legislatures have proposed laws to prohibit abortion once the earliest embryonic electrical activity is detectable (fetal "heartbeat"). On average, this occurs roughly 6 wk after the last menstrual period. To be eligible for abortion, people must recognize pregnancy very early in gestation. The earliest symptom of pregnancy is a missed period, and irregular menstrual cycles-which occur frequently-can delay pregnancy detection past the point of fetal cardiac activity. In our analysis of 1.6 million prospectively recorded menstrual cycles, cycle irregularity was more common among young women, Hispanic women, and women with common health conditions, such as diabetes and polycystic ovary syndrome. These groups face physiological limitations in detecting pregnancy before fetal cardiac activity. Restriction of abortion this early in gestation differentially affects specific population subgroups, for reasons outside of individual control.

GWAS on birth year infant mortality rates provides evidence of recent natural selection.

Following more than a century of phenotypic measurement of natural selection processes, much recent work explores relationships between molecular genetic measurements and realized fitness in the next generation. We take an innovative approach to the study of contemporary selective pressure by examining which genetic variants are "sustained" in populations as mortality exposure increases. Specifically, we deploy a so-called "regional GWAS" (genome-wide association study) that links the infant mortality rate (IMR) by place and year in the United Kingdom with common genetic variants among birth cohorts in the UK Biobank. These cohorts (born between 1936 and 1970) saw a decline in IMR from above 65 to under 20 deaths per 1,000 live births, with substantial subnational variations and spikes alongside wartime exposures. Our results show several genome-wide significant loci, including LCT and TLR10/1/6, related to area-level cohort IMR exposure during gestation and infancy. Genetic correlations are found across multiple domains, including fertility, cognition, health behaviors, and health outcomes, suggesting an important role for cohort selection in modern populations.

The Unequal Impact of the COVID-19 Pandemic on Infant Health.

The COVID-19 pandemic has taken a large toll on population health and well-being. We examine the consequences of prenatal exposure for infant health, through which the pandemic may have lasting intergenerational effects. We examine multiple pathways by which the pandemic shaped birth outcomes and socioeconomic disparities in these consequences. Analysis of more than 3.5 million birth records in California with universal information on COVID infection among persons giving birth at the time of delivery reveals deep inequalities in infection by education, race/ethnicity, and place-based socioeconomic disadvantage. COVID infection during pregnancy, in turn, predicts a large increase in the probability of preterm birth, by approximately one third. At the population level, a surprising reduction in preterm births during the first months of the pandemic was followed by an increase in preterm births during the surge in COVID infections in the winter of 2021. Whereas the early-pandemic reduction in preterm births benefited primarily highly educated mothers, the increase in preterm births during the winter infection surge was entirely concentrated among mothers with low levels of schooling. The COVID-19 pandemic is expected to exacerbate U.S. inequality in multiple ways. Our findings highlight a particularly enduring pathway: the long-term legacy of prenatal exposure to an unequal pandemic environment.

Network resources and educational outcomes among Mexican-origin youth.

Despite schooling gains over the last two decades, Mexican-origin adults complete fewer years of schooling than adults from other ethnic backgrounds. Explanations emphasizing network resources suggest Mexican-origin adolescents have social ties that are more likely to be "closed" from adults with experience in higher education-and this, in turn, inhibits the transition to college. In this study, we draw on unusual network data measuring characteristics of students' peers and friends, as well as the socioeconomic background of peers' and friends' parents. We demonstrate that Mexican-origin adolescents are much less likely to have friends whose parents have college educations. 83% of non-Hispanic Asian students and 72% of non-Hispanic white students have nominated friends with college-educated mothers; about half of Mexican-origin students do. These patterns are the result of socioeconomic segregation in social networks both across and within schools. Within schools, we observe that the educational background of friends is predictive of schooling outcomes for non-Mexican students. We find evidence that this network resource shapes non-Mexican students' educational expectations in high school and longer-run completed schooling as adults more so than it shapes the outcomes among Mexican-origin students.

Brazil's Missing Infants: Zika Risk Changes Reproductive Behavior.

Zika virus epidemics have potential large-scale population effects. Controlled studies of mice and nonhuman primates indicate that Zika affects fecundity, raising concerns about miscarriage in human populations. In regions of Brazil, Zika risk peaked months before residents learned about the epidemic and its relation to congenital anomalies. This spatiotemporal variation supports analysis of both biological effects of Zika infection on fertility and the effects of learning about Zika risk on reproductive behavior. Causal inference techniques used with vital statistics indicate that the epidemic caused reductions in birth cohort size of approximately one-quarter 18 months after Zika infection risk peaked but 10 months after public health messages advocated childbearing delay. The evidence is consistent with small but not statistically detectable biological reductions in fecundity, as well as large strategic changes in reproductive behavior to temporally align childbearing with reduced risk to infant health. The behavioral effects are larger for more-educated and older women, which may reflect facilitated access to information and to family planning services within high-risk, mosquito-infested urban locations as well as perceptions about the opportunity costs of risks to pregnancy and infant survival.

Meeting the Institute of Medicine's 2030 US Life Expectancy Target.

OBJECTIVES: To quantify the improvement in US life expectancy required to reach parity with high-resource nations by 2030, to document historical precedent of this rate, and to discuss the plausibility of achieving this rate in the United States. METHODS: We performed a demographic analysis of secondary data in 5-year periods from 1985 to 2015. RESULTS: To achieve the United Nations projected mortality estimates for Western Europe in 2030, the US life expectancy must grow at 0.32% a year between 2016 and 2030. This rate has precedent, even in low-mortality populations. Over 204 country-periods examined, nearly half exhibited life-expectancy growth greater than 0.32%. Of the 51 US states observed, 8.2% of state-periods demonstrated life-expectancy growth that exceeded the 0.32% target. CONCLUSIONS: Achieving necessary growth in life expectancy over the next 15 years despite historical precedent will be challenging. Much all-cause mortality is structured decades earlier and, at present, older-age mortality reductions in the United States are decelerating. Addressing mortality decline at all ages will require enhanced political will and a strong commitment to equity improvement in the US population.

Migration and Parental Absence: A Comparative Assessment of Transnational Families in Latin America.

Despite growing research on transnational families and children's welfare in migrant-sending countries, there is a dearth of information about the prevalence of, what we call, parental absence via migration, especially relative to other sources of parental absence, and a lack of estimates that are comparable across populations and places. This makes it difficult to determine the scale for policy interventions, and to justify future research on transnational families and children's welfare. Using harmonized surveys covering eight Latin American countries and Puerto Rico, validated by nationally representative census and survey data, we provide the first estimates of the prevalence parental absence via migration that are comparable across populations in contemporary Latin America. We show that between 7 and 21 percent of children live in transnational families where parents are absent because of migration. We compare our estimates to similar estimates of parental absence from other sources, and show that, in several populations, more children are experiencing parental absence due to migration than to union dissolution or parental mortality. Finally, we link our descriptive work to children's welfare by examining the characteristics of children's home environments when parents migrate. Children living in families with absent parents due to migration are less likely to coreside with extended family members, and to fare better in terms of household assets, relative to children living in other family forms. We conclude by highlighting the limitations of the data, and underscore the value of attempts to estimate the prevalence of parental absence via migration.

Engaged parenting, gender, and children's time use in transnational families: An assessment spanning three global regions.

Global circuits of migration regularly separate parents from children. How families navigate this separation has changed markedly. The sharp decline in the cost of international communication makes possible new forms of transnational parenting. In many contexts, migrants are now actively engaged parents, involved in decisions, knowledgeable of children's schooling, employment, and activities, and in some cases, even conversant face-to-face with children via videoconferencing. These practices, however, are not universal. We use data from surveys in three countries to document the frequency and variability of intensive, engaged transnational parenting in the diverse global regions of Asia, Africa, and the Americas. We then ask whether the organisation of children's lives-specifically, time allocated to school homework, leisure, and household chores-varies by the degree to which migrant parents stay connected to sending homes. The gender of the migrant parent, stay-behind caregiver, and the gender of the child emerge as explanatory factors for engaged parenting and children's time use. However, and unexpectedly, in the Philippines, migrant mothers are less likely to practice engaged parenting. In sending households, girls in two of the three countries spend more time doing household chores than boys, but parental migration does not mitigate this difference. Although we find some evidence of more traditional gender practices, we also find exceptions that suggest potentially fruitful avenues for future research.

Post-Disaster Fertility: Hurricane Katrina and the Changing Racial Composition of New Orleans.

Large-scale climate events can have enduring effects on population size and composition. Natural disasters affect population fertility through multiple mechanisms, including displacement, demand for children, and reproductive care access. Fertility effects, in turn, influence the size and composition of new birth cohorts, extending the reach of climate events across generations. We study these processes in New Orleans during the decade spanning Hurricane Katrina. We combine census data, ACS data, and vital statistics data to describe fertility in New Orleans and seven comparison cities. Following Katrina, displacement contributed to a 30% decline in birth cohort size. Black fertility fell, and remained 4% below expected values through 2010. By contrast, white fertility increased by 5%. The largest share of births now occurs to white women. These fertility differences-beyond migration-driven population change-generate additional pressure on the renewal of New Orleans as a city in which the black population is substantially smaller in the disaster's wake.

Gender, Power, and Emigration From Mexico.

The prevailing model of migration in developing countries conceives of a risk-diversifying household in which members act as a single entity when making migration decisions. Ethnographic studies challenge this model by documenting gender hierarchy in family decisions and arguing that, in many contexts, men and women have differing views on the value of migration. We assess these perspectives using longitudinal survey data from Mexico. We show that Mexican households are heterogeneous in terms of women's decision-making authority and control over resources, and this variation predicts the subsequent emigration of their male partners to the United States. We then use data from a policy experiment to demonstrate that an exogenous increase in a woman's control over household resources decreases the probability that her spouse migrates. Our findings support the presence of important gender differences in how migration is valued. They also suggest that women's role in these decisions is inadvertently underrepresented in studies of migrant families. Staying is also a migration decision, and it is more likely in homes in which women have greater authority. From a policy perspective, the results suggest that Mexican migration is influenced not only by increases in household resources but also by which members of the household control them.

Fertility rates in women with intellectual and developmental disabilities in Wisconsin Medicaid.

BACKGROUND: Women with intellectual and developmental disabilities (IDD) face stigma and inequity surrounding opportunity and care during pregnancy. Little work has quantified fertility rates among women with IDD which prevents proper allocation of care. OBJECTIVE: Our objective was to cross-sectionally describe fertility patterns among women with and without intellectual and developmental disabilities (IDD) in 10-years of Medicaid-linked birth records. STUDY DESIGN: Our sample was Medicaid-enrolled women with live births in Wisconsin from 2007 to 2016. We identified IDD through prepregnancy Medicaid claims. We calculated general fertility-, age-specific-, and the total fertility-rates and 95% confidence intervals (95% CI) for women with and without IDD and generated estimates by year and IDD-type. RESULTS: General fertility rate in women with IDD was 62.1 births per 1000 women with IDD (95% CI 59.2, 64.9 per 1000 women) and 77.1 per 1000 for women without IDD (95% CI: 76.8, 77.4 per 1000 women). General fertility rate ratio was 0.81 (95% CI: 0.7, 0.9). Total fertility was 1.80 births per woman with IDD and 2.05 births per woman without IDD (rate ratio: 0.89 95% CI: 0.5, 1.5). Peak fertility occurred later for autistic women (30-34 years), compared with women with other IDD (20-24 years). CONCLUSION: In Wisconsin Medicaid, general fertility rate of women with IDD was lower than women without IDD: the difference was attenuated when accounting for differing age distributions. Results highlight the disparities women with IDD face and the importance of allocating pregnancy care within Medicaid.

Mothers' community participation and child health.

We use rich data from the Indonesia Family Life Survey to assess the relationship between mothers' access to social capital via participation in community activities and their children's health. We exploit the advantages of longitudinal data and community fixed effects to mitigate some of the concerns about spuriousness and reverse causality that predominate in this literature. We find that children from families with relatively low levels of human and financial capital fare better with respect to health status when their mothers are more active participants in community organizations. In fact, the association between maternal participation and child health is strong and positive only for children from relatively disadvantaged backgrounds, as measured by their mothers' educational and household economic resources. The results suggest that in poorer settings community involvement may benefit disadvantaged families, possibly by providing resources and information that would otherwise be inaccessible.

Ethnic diversity, traditional norms, and marriage behaviour in Indonesia.

What role do cultural norms play in shaping individual behaviour and how does this relationship change with rapid socio-economic development? While modernization and convergence theories predict a weakened relationship between culture and behaviour as individuals rely less on family and community members for economic opportunities, recent research suggests that such norms can persist and continue to influence behaviour. We explored this question for Indonesia, asking whether cultural norms for age at marriage and post-marriage residence-as embodied in local ethnicity-based laws and customs known as 'adat'-relate to actual marriage behaviour. We demonstrate that adat norms are strong predictors of marriage behaviour, both over time and net of large increases in educational attainment. Our results suggest more generally that traditional marriage norms can persist even when a society is in the process of rapid socio-economic development.

Detecting the Effects of Early-Life Exposures: Why Fecundity Matters.

Prenatal exposures have meaningful effects on health across the lifecourse. Innovations in causal inference have shed new light on these effects. Here, we motivate the importance of innovation in the characterization of fecundity, and prenatal selection in particular. We argue that such innovation is crucial for expanding knowledge of the fetal origins of later life health. Pregnancy loss is common, responsive to environmental factors, and closely related to maternal and fetal health outcomes. As a result, selection into live birth is driven by many of the same exposures that shape the health trajectories of survivors. Lifecourse effects that are inferred without accounting for these dynamics may be significantly distorted by survival bias. We use a set of Monte Carlo simulations with realistic parameters to examine the implications of prenatal survival bias. We find that even in conservatively specified scenarios, true fetal origin effects can be underestimated by 50% or more. In contrast, effects of exposures that reduce the probability of prenatal survival but improve the health of survivors will be overestimated. The absolute magnitude of survival bias can even exceed small effect sizes, resulting in inferences that beneficial exposures are harmful or vice-versa. We also find reason for concern that moderately sized true effects, underestimated due to failure to account for selective survival, are missing from scientific knowledge because they do not clear statistical significance filters. This bias has potential real-world costs; policy decisions about interventions to improve maternal and infant health will be affected by underestimated program impact.

The effects of mortality on fertility: population dynamics after a natural disaster.

Understanding how mortality and fertility are linked is essential to the study of population dynamics. We investigate the fertility response to an unanticipated mortality shock that resulted from the 2004 Indian Ocean tsunami, which killed large shares of the residents of some Indonesian communities but caused no deaths in neighboring communities. Using population-representative multilevel longitudinal data, we identify a behavioral fertility response to mortality exposure, both at the level of a couple and in the broader community. We observe a sustained fertility increase at the aggregate level following the tsunami, which was driven by two behavioral responses to mortality exposure. First, mothers who lost one or more children in the disaster were significantly more likely to bear additional children after the tsunami. This response explains about 13 % of the aggregate increase in fertility. Second, women without children before the tsunami initiated family-building earlier in communities where tsunami-related mortality rates were higher, indicating that the fertility of these women is an important route to rebuilding the population in the aftermath of a mortality shock. Such community-level effects have received little attention in demographic scholarship.

After spouses depart: emotional wellbeing among nonmigrant Mexican mothers.

Nonmigrant family members play a central role in facilitating Mexico-U.S. migration by maintaining families, sustaining social relationships, and overseeing household economic organization in sending communities. This study investigates changes to the emotional wellbeing of nonmigrant mothers when their partners reside in the United States. We hypothesize that partner migration affects mothers' wellbeing through three pathways: directly via the toll of spousal separation, and indirectly via changes to the economic profile of the sending household and through changes to mothers' household responsibilities. We test these relationships using data on 2813 mothers aged 18-44 in 2002 and measured in three waves (2002, 2005, 2009) of the Mexican Family Life Survey. We employ a fixed-effect estimation strategy that improves causal attribution of women's wellbeing to spousal residential location. We find evidence of increases in some forms of distress-sadness, crying, difficulty sleeping-when spouses are in the United States but no meaningful increase in depressive symptomology. Though partner emigration shifts several aspects of women's lives in sending households, changes to household resources or time allocation do not account for the moderate shifts in emotional duress associated with spousal absence. Importantly, additional tests reveal that we would observe large and significant associations between spousal migration and mothers' emotional wellbeing using a less rigorous estimation strategy, raising caution about the interpretation of cross-sectional studies evaluating wellbeing in sending homes.

Substance Use Across Different Phases of the Migration Process: A Survey of Mexican Migrants Flows.

This study examined the levels of substance use and changes across different migration stages, including pre-departure, travel, destination, and return, among Mexican migrants converging on the US-Mexico border. A cross-sectional survey was conducted in Tijuana, Mexico, between 2009 and 2010 among Mexican migrants returning from the US and those travelling from other Mexican regions. The overall prevalence of last 12-month at-risk drinking, illicit drug use, and current smoking, was 42.3, 17.7 and 31.4%, respectively. Compared to pre-departure migrants, males were at increased risk for illicit drug use at the destination and return stages. In contrast, females' alcohol consumption at the destination stage was lower than at pre-departure (p < 0.05). The level of smoking was stable across all stages for both genders. In the destination stage, undocumented migrants were more likely to use illicit drugs relative to their documented peers (p < 0.05). Binational interventions promoting substance use reduction are needed among this mobile population.

Dependency, democracy, and infant mortality: a quantitative, cross-national analysis of less developed countries.

This study presents quantitative, sociological models designed to account for cross-national variation in infant mortality rates. We consider variables linked to four different theoretical perspectives: the economic modernization, social modernization, political modernization, and dependency perspectives. The study is based on a panel regression analysis of a sample of 59 developing countries. Our preliminary analysis based on additive models replicates prior studies to the extent that we find that indicators linked to economic and social modernization have beneficial effects on infant mortality. We also find support for hypotheses derived from the dependency perspective suggesting that multinational corporate penetration fosters higher levels of infant mortality. Subsequent analysis incorporating interaction effects suggest that the level of political democracy conditions the effects of dependency relationships based upon exports, investments from multinational corporations, and international lending institutions. Transnational economic linkages associated with exports, multinational corporations, and international lending institutions adversely affect infant mortality more strongly at lower levels of democracy than at higher levels of democracy: intranational, political factors interact with the international, economic forces to affect infant mortality. We conclude with some brief policy recommendations and suggestions for the direction of future research.

Do daughters really cause divorce? Stress, pregnancy, and family composition.

Provocative studies have reported that in the United States, marriages producing firstborn daughters are more likely to divorce than those producing firstborn sons. The findings have been interpreted as contemporary evidence of fathers' son preference. Our study explores the potential role of another set of dynamics that may drive these patterns: namely, selection into live birth. Epidemiological evidence indicates that the characteristic female survival advantage may begin before birth. If stress accompanying unstable marriages has biological effects on fecundity, a female survival advantage could generate an association between stability and the sex composition of offspring. Combining regression and simulation techniques to analyze real-world data, we ask, How much of the observed association between sex of the firstborn child and risk of divorce could plausibly be accounted for by the joint effects of female survival advantage and reduced fecundity associated with unstable marriage? Using data from the National Longitudinal Survey of Youth (NLSY79), we find that relationship conflict predicts the sex of children born after conflict was measured; conflict also predicts subsequent divorce. Conservative specification of parameters linking pregnancy characteristics, selection into live birth, and divorce are sufficient to generate a selection-driven association between offspring sex and divorce, which is consequential in magnitude. Our findings illustrate the value of demographic accounting of processes which occur before birth-a period when many outcomes of central interest in the population sciences begin to take shape.