Maternal exposure to unexpected economic contraction and birth weight for gestational age

Perinatal health in Spain during and after the Great Recession: Educational selection into fertility as a protective factor in high unemployment contexts

Higher maternal resources have long been associated with superior birth outcomes. This study analyzes the potentially protective role of maternal educational selection into fertility in adverse macroeconomic contexts. We focus on the case of Spain, a country reaching record-high unemployment levels during the Great Recession starting in 2008. First, we examine whether selection into fertility of more educated mothers took place as province-level unemployment rates rose. Secondly, we assess whether maternal education mitigated the impact of higher unemployment levels on different birth outcomes. The analysis combines register data on the universe of live births with aggregate data on province-level unemployment. We cover the period 2007-2019 to ensure sufficient variability of unemployment rates and perform linear regression and linear probability models with fixed effects to hold constant unobserved heterogeneity across provinces. Findings indicate selection into fertility of mothers with university-level education in times of high unemployment. In addition, while unemployment rates did show an adverse impact on certain birth outcomes -birthweight, the occurrence of low and very low birthweight, and the risk of stillbirth - maternal education mitigated the observed relations. It was itself, moreover, consistently and independently associated with better perinatal health. We thus conclude that fertility selectivity by maternal education cushioned the impact of the adverse economic context derived from the Great Recession through two separate pathways.

Outcomes and Disease Spectrum of LBW Neonates in a Secondary Health Facility

Globally, 30 million low birth weight (LBW) babies are born every year and 95% of them are from developing countries. LBW neonates are at a high risk of mortality, morbidity, and long-term disability. The objective of this study is to investigate outcomes and disease spectrum among low birth weight neonates. This is a prospective, observational study conducted on 540 neonates admitted in the Mother and Child Hospital, Akure, Ondo State, Nigeria, from 2017 to 2018. Questionnaire, interview, clinical, and diagnostic procedures were used as research tools. There were 137 low birth weight (LBW) neonates, with the mean mothers’ age of 31.92 ± 6.60. Of the 540 neonates, 69 (50.4%) and 68 (49.6%) were term and preterm, respectively. There were 64 female neonates (46.7%) and 73 male neonates (53.3%). The mean weight of the neonates was 1.82 ± 0.44 kg, and mean number of days on admission was 6.42 ± 6.75 days. Neonatal sepsis (NNS) was the highest morbidity 51 (37.2%) among the LBW neonates, followed by prematurity 47 (34.4%) and neonatal jaundice (NNJ) 18 (13.1%). Sex (χ2 = 3.584, $p=0.310$ ), mode of delivery (χ2 = 4.669, $p=0.198$ ), and gestational age (χ2 = 3.904, $p=0.272$ ) were not a significant determinant of outcome among LBW neonates. Men were 2.36 times more likely to be preterm (OR = 2.36, 95% CL = 1.01–5.54, $p=0.048$ ) among LBW neonates. Outcomes of LBW neonates who were delivered by SVD were not significant compared to preterm delivered by CS (OR = 0.46, 95% CL = 0.13–1.65, $p=0.096$ ). Sixty percent (60%) of the mothers had Prolonged Rupture of Membranes (PROM). Morbidities such as hypothermia (72.2%), apnoea (63.6%), haemorrhagic disease of the newborn (HDN) (66.7%), and respiratory distress syndrome (RDS) (66.7%) were more observed with preterm LBW neonates. Importance of qualitative antenatal care (ANC) should be emphasized; anticipation and prevention of LBW births can help mitigate some of the problems they are prone to.

Postpartum medical utilization: The role of prenatal economic activity and living costs

This study is the first to explore the extent to which prenatal economic fluctuations affect postpartum outpatient care utilization during three-month, six-month, and one-year postpartum periods in Taiwan and to document their counter-cyclical patterns for economic activity and pro-cyclical patterns for the CPI change rate. We present evidence that medical care utilization occurring during the postpartum period is sensitive to economic activity within the first trimester of pregnancy and the CPI change rate within the second trimester. The findings herein reveal that negative prenatal economic shocks lead to a higher probability of cesarean section, more outpatient visits for depressive disorders, hypertension, gestational diabetes, and anemia in the pregnancy period, and a lower number of prenatal care visits that could deteriorate postpartum maternal health. Moreover, our results are consistent with low-salary and private-sector-employed mothers who face credit constraints and experience the risk of losing their job, respectively, during a decline in economic activity and who subsequently suffer from nutritional deficits and maternal stress that lead to postpartum health deterioration. Conversely, high-salary mothers do not face credit constraints and have greater coping ability to deal with stress and nutritional problems, while public-sector-employed mothers are affected only by nutrition.

Maternal Education in Early Life and Risk of Metabolic Syndrome in Young Adult American Females and Males: Disentangling Life Course Processes Through Causal Models

BACKGROUND

Maternal education in a child's early life may directly affect the child's adult cardiometabolic health, but this is difficult to disentangle from biological, social, and behavioral life course processes that are associated with maternal education. These processes may also differ between males and females.

METHODS

Using data from the National Longitudinal Study of Adolescent to Adult Health (1995-2009) (N = 4,026 females and 3,192 males), we estimated sex-stratified associations between maternal attainment of less than high school (<HS), high school diploma (HS), or college degree (CD) at the respondent's birth and respondent's risk of metabolic syndrome (MetS); we used marginal structural models (MSM) to account for the influence of major life course risk factors, such as childhood maltreatment, adolescent overweight, adult education, household income, smoking, and physical activity, in mediating associations between maternal education and offspring MetS risk.

RESULTS

Each higher level of maternal education was associated with a 36% (Relative Risk = 0.64 [95% Confidence Interval (CI): 0.50-0.82]) reduced risk of MetS among females, but only 19% (RR = 0.81 [95% CI: 0.64-1.01]) reduction among males (P-value interaction < 0.05). Stronger inverse associations were also observed for waist circumference and glycated hemoglobin (HbA1c) among females compared with males (-5 cm vs. -2.4 cm and -1.5% vs. -1.0%, respectively).

CONCLUSION

High maternal education in early life was associated with a lower risk of MetS in young adulthood even after accounting for life course risk factors, particularly among females. Results were robust to altered model specifications.

Newborn health and the business cycle: The role of birth order

We use 35 years of administrative data to document how newborn health varies with the business cycle in Spain. In panel regressions that include province and year fixed effects as well as province trends, we show that children have significantly better health outcomes at birth in times of high unemployment: a 10 percentage-point increase in the unemployment rate is significantly associated with about 2 log-points higher birth-weight, almost 2 percentage points fewer babies with low birth weight, 0.6 points fewer babies with very low birth-weight, and a 0.4-point drop in mortality rates in the first 24 h We explore several potential mechanisms. First, we show that the documented association is not driven by in-utero selection: we do not find that high unemployment is associated with more miscarriages, abortions, or stillbirths. Second, we explore the role of composition in terms of parental characteristics. We find evidence that unmarried and younger parents, who typically have unhealthier babies, are relatively less likely to have children when unemployment is high. Finally, we show that there are fewer first births during recessions, and birth order is strongly positively correlated with health at birth. Birth order can account for up to one fifth of the countercyclicality of birth weight.

Immigrant apprehensions and birth outcomes: Evidence from California birth records 2008-2015

While several studies find adverse birth outcomes among Latina mothers after discrete immigration enforcement events, it is unknown whether day-to-day enforcement activities precede adverse birth outcomes. This study examines birth outcomes among Latinas following local immigrant apprehensions-48-h holds on suspected undocumented immigrants by local law enforcement-over an 8-year period. County-level apprehensions, scaled to 1000 of the population, were averaged across the third trimester. We analyzed the association between county-level apprehensions and low birth weight (LBW) and preterm birth (PTB) between 2008 and 2015 in California using spline logistic regression models with knots at the quartiles of apprehensions and included covariates, county fixed-effects, and a time propensity variable to account for trend and seasonality in LBW and PTB. We performed these regressions for non-Hispanic White, all Latina, and foreign-born (FB) Latina mothers. There were no significant associations between apprehensions and LBW. For all Latina women, there were no differences in PTB between zero apprehensions and levels that were below the median. Latina mothers exposed to moderately high apprehensions had lower odds for PTB compared to zero apprehensions. At the highest levels of apprehensions, however, Latina women showed significantly elevated odds of PTB (at 0.71 apprehensions: OR = 1.06, 95% CI 1.01-1.12). PTB responded differentially to localized enforcement threats. At lower and moderate levels, Latino communities may have mobilized in ways that reduced the risk for PTB. Risks emerged at the highest levels of enforcement, underlying the intense fear and anxiety in hyper-surveilled areas.

Social determinants of health and disparities in prenatal care utilization during the Great Recession period 2005-2010

BACKGROUND

Early, regular prenatal care utilization is an important strategy for improving maternal and infant health outcomes. The purpose of this study is to better understand contributing factors to disparate prenatal care utilization outcomes among women of different racial/ethnic and social status groups before, during, and after the Great Recession (December 2007-June 2009).

METHODS

Data from 678,235 Washington (WA) and Florida (FL) birth certificates were linked to community and state characteristic data to carry out cross-sectional pooled time series analyses with institutional review board approval for human subjects' research. Predictors of on-time as compared to late or non-entry to prenatal care utilization (late/no prenatal care utilization) were identified and compared among pregnant women. Also explored was a simulated triadic relationship among time (within recession-related periods), social characteristics, and prenatal care utilization by clustering individual predictors into three scenarios representing low, average, and high degrees of social disadvantage.

RESULTS

Individual and community indicators of need (e.g., maternal Medicaid enrollment, unemployment rate) increased during the Recession. Associations between late/no prenatal care utilization and individual-level characteristics (including disparate associations among race/ethnicity groups) did not shift greatly with young maternal age and having less than a high school education remaining the largest contributors to late/no prenatal care utilization. In contrast, individual maternal enrollment in a supplemental nutrition program for women, infants, and children (WIC) exhibited a protective association against late/no prenatal care utilization. The magnitude of association between community-level partisan voting patterns and expenditures on some maternal child health programs increased in non-beneficial directions. Simulated scenarios show a high combined impact on prenatal care utilization among women who have multiple disadvantages.

CONCLUSIONS

Our findings provide a compelling picture of the important roles that individual characteristics-particularly low education and young age-play in late/no prenatal care utilization among pregnant women. Targeted outreach to individuals with high disadvantage characteristics, particularly those with multiple disadvantages, may help to increase first trimester entry to utilization of prenatal care. Finally, WIC may have played a valuable role in reducing late/no prenatal care utilization, and its effectiveness during the Great Recession as a policy-based approach to reducing late/no prenatal care utilization should be further explored.

Economic Downturns and Inequities in Birth Outcomes: Evidence From 149 Million US Births

Using birth certificate data for nearly all registered US births from 1976 to 2016 and monthly data on state unemployment rates, we reexamined the link between macroeconomic variation and birth outcomes. We hypothesized that economic downturns reduce exposure to work-related stressors and pollution while increasing exposure to socioeconomic stressors like job loss. Because of preexisting inequalities in health and other resources, we expected that less-educated mothers and black mothers would be more exposed to macroeconomic variation. Using fixed-effect regression models, we found that a 1-percentage-point increase in state unemployment during the first trimester of pregnancy increased the probability of preterm birth by 0.1 percentage points, while increases in the state unemployment rate during the second/third trimester reduced the probability of preterm birth by 0.06 percentage points. During the period encompassing the Great Recession, the magnitude of these associations doubled in size. We found substantial variation in the impact of economic conditions across different groups, with highly educated white women least affected and less-educated black women most affected. The results highlight the increased relevance of economic conditions for birth outcomes and population health as well as continuing, large inequities in the exposure and impact of macroeconomic fluctuations on birth outcomes.

Subprime Babies: The Foreclosure Crisis and Initial Health Endowments

The subprime mortgage crisis was a devastating financial shock for many homeowners. This research uses a probabilistic matching strategy to link foreclosure records with birth certificate records from 2006 to 2010 in California to identify birth parents who experienced a foreclosure. Among mothers who did, those issued a loan during the peak of subprime lending from 2005 to 2007 were more Hispanic and socioeconomically disadvantaged than mothers with loans originating before 2005. We use a mother fixed-effects analyses of ever-foreclosed mothers issued a loan during 2006 and 2007 and find that infants in gestation during or after the foreclosure had a lower birth weight for gestational age than those born earlier, suggesting that the foreclosure crisis was a plausible contributor to disparities in initial health endowments.

Economic conditions during pregnancy and preterm birth: A maternal fixed-effects analysis

BACKGROUND

Making causal inference regarding impacts of macrolevel economic conditions during pregnancy on pregnancy outcomes is hampered by the presence of unmeasured variables that may influence women's probability of giving birth under certain economic conditions (ie, exposure) as well as her pregnancy outcomes. Maternal fixed-effects (FE) analyses, in which the association between exposure and outcomes is estimated within mothers who had discordant outcomes, can control for such unmeasured variables when they are invariant across pregnancies.

METHODS

We utilised a maternally linked data set of all singleton births in Michigan from 1990 to 2012 (n = 2 657 272 for full sample; n = 269 943 for FE analytic sample) to examine the relationship between state-level unemployment rates during pregnancy and preterm birth (PTB, <37 weeks' gestation). Measured maternal characteristics that change across pregnancies, for example, age, marital status, education, parity, and infant sex, were included as covariates in the model.

RESULTS

Using an FE approach, we found that each one percentage point increase in state unemployment in the first trimester of pregnancy was associated with a modest 3% increase in odds of PTB. Our results were consistent with previously published results in a national sample and held across random- versus fixed-effect models, analytic samples, and outcome measures.

CONCLUSIONS

Our findings provide further evidence that economic downturn during early pregnancy may be associated with modest increases in PTB.

Prenatal Exposure to an Acute Stressor and Children's Cognitive Outcomes

Exposure to environmental stressors is highly prevalent and unequally distributed along socioeconomic lines and may have enduring negative consequences, even when experienced before birth. Yet, estimating the consequences of prenatal stress on children's outcomes is complicated by the issue of confounding (i.e., unobserved factors correlated with stress exposure and with children's outcomes). I combine a natural experiment-a strong earthquake in Chile-with a panel survey to capture the effect of prenatal exposure on acute stress and children's cognitive ability. I find that stress exposure in early pregnancy has no effect on children's cognition among middle-class families, but it has a strong negative influence among disadvantaged families. I then examine possible pathways accounting for the socioeconomic stratification in the effect of stress, including differential exposure across socioeconomic status, differential sensitivity, and parental responses. Findings suggest that the interaction between prenatal exposures and socioeconomic advantage provides a powerful mechanism for the intergenerational transmission of disadvantage.

Economic downturns and infant health

We study the gender-specific impact of macroeconomic conditions around birth on infant health. We use a sample of over 50,000 respondents born between 1950 and 1994 from Lifelines-a cohort and biobank from the northern Netherlands. Our results show that high provincial unemployment rates decrease fertility and lead to a lower birthweight in boys. The negative impact of high unemployment on birthweight is particularly strong for boys born to older mothers and for babies born to smoking mothers.

Economic Conditions During Pregnancy and Adverse Birth Outcomes Among Singleton Live Births in the United States, 1990-2013

We know little about the relationship between the macroeconomy and birth outcomes, in part due to the methodological challenge of distinguishing effects of economic conditions on fetal health from effects of economic conditions on selection into live birth. We examined associations between state-level unemployment rates in the first 2 trimesters of pregnancy and adverse birth outcomes, using natality data on singleton live births in the United States during 1990-2013. We used fixed-effect logistic regression models and accounted for selection by adjusting for state-level unemployment before conception and maternal characteristics associated with both selection and birth outcomes. We also tested whether associations between macroeconomic conditions and birth outcomes differed during and after (compared with before) the Great Recession (2007-2009). Each 1-percentage-point increase in the first-trimester unemployment rate was associated with a 5% increase in odds of preterm birth, while second-trimester unemployment was associated with a 3% decrease in preterm birth odds. During the Great Recession, however, first-trimester unemployment was associated with a 16% increase in odds of preterm birth. These findings increase our understanding of the effects of the Great Recession on health and add to growing literature suggesting that macro-level social and economic factors contribute to perinatal health.

Change in birth outcomes among infants born to Latina mothers after a major immigration raid

Background

Growing evidence indicates that immigration policy and enforcement adversely affect the well-being of Latino immigrants, but fewer studies examine 'spillover effects' on USA-born Latinos. Immigration enforcement is often diffuse, covert and difficult to measure. By contrast, the federal immigration raid in Postville, Iowa, in 2008 was, at the time, the largest single-site federal immigration raid in US history.

Methods

We employed a quasi-experimental design, examining ethnicity-specific patterns in birth outcomes before and after the Postville raid. We analysed Iowa birth-certificate data to compare risk of term and preterm low birthweight (LBW), by ethnicity and nativity, in the 37 weeks following the raid to the same 37-week period the previous year ( n  =   52 344). We model risk of adverse birth outcomes using modified Poisson regression and model distribution of birthweight using quantile regression.

Results

Infants born to Latina mothers had a 24% greater risk of LBW after the raid when compared with the same period 1 year earlier [risk ratio (95% confidence interval) = 1.24 (0.98, 1.57)]. No such change was observed among infants born to non-Latina White mothers. Increased risk of LBW was observed for USA-born and immigrant Latina mothers. The association between raid timing and LBW was stronger among term than preterm births. Changes in birthweight after the raid primarily reflected decreased birthweight below the 5th percentile of the distribution, not a shift in mean birthweight.

Conclusions

Our findings highlight the implications of racialized stressors not only for the health of Latino immigrants, but also for USA-born co-ethnics.

Pregnancy: An Underutilized Window of Opportunity to Improve Long-term Maternal and Infant Health-An Appeal for Continuous Family Care and Interdisciplinary Communication

Physiologic adaptations during pregnancy unmask a woman's predisposition to diseases. Complications are increasingly predicted by first-trimester algorithms, amplify a pre-existing maternal phenotype and accelerate risks for chronic diseases in the offspring up to adulthood (Barker hypothesis). Recent evidence suggests that vice versa, pregnancy diseases also indicate maternal and even grandparent's risks for chronic diseases (reverse Barker hypothesis). Pub-Med and Embase were reviewed for Mesh terms "fetal programming" and "pregnancy complications combined with maternal disease" until January 2017. Studies linking pregnancy complications to future cardiovascular, metabolic, and thrombotic risks for mother and offspring were reviewed. Women with a history of miscarriage, fetal growth restriction, preeclampsia, preterm delivery, obesity, excessive gestational weight gain, gestational diabetes, subfertility, and thrombophilia more frequently demonstrate with echocardiographic abnormalities, higher fasting insulin, deviating lipids or clotting factors and show defective endothelial function. Thrombophilia hints to thrombotic risks in later life. Pregnancy abnormalities correlate with future cardiovascular and metabolic complications and earlier mortality. Conversely, women with a normal pregnancy have lower rates of subsequent diseases than the general female population creating the term: "Pregnancy as a window for future health." Although the placenta works as a gatekeeper, many pregnancy complications may lead to sickness and earlier death in later life when the child becomes an adult. The epigenetic mechanisms and the mismatch between pre- and postnatal life have created the term "fetal origin of adult disease." Up to now, the impact of cardiovascular, metabolic, or thrombotic risk profiles has been investigated separately for mother and child. In this manuscript, we strive to illustrate the consequences for both, fetus and mother within a cohesive perspective and thus try to demonstrate the complex interrelationship of genetics and epigenetics for long-term health of societies and future generations. Maternal-fetal medicine specialists should have a key role in the prevention of non-communicable diseases by implementing a framework for patient consultation and interdisciplinary networks. Health-care providers and policy makers should increasingly invest in a stratified primary prevention and follow-up to reduce the increasing number of manifest cardiovascular and metabolic diseases and to prevent waste of health-care resources.

Prenatal exposure to violence and birth weight in Mexico: Selectivity, exposure, and behavioral responses

This article examines the effect of maternal exposure to local homicides on birth weight. We create a monthly panel by merging all births in Mexico from 2008 to 2010 with homicide data at the municipality level. Findings from fixed-effects models indicate that exposure to homicides in the first trimester of gestation increases infant birth weight and reduces the proportion of low birth weight. The effect is not driven by fertility or migration responses to environmental violence. The mechanism driving this surprising positive effect appears to be an increase in mothers’ health-enhancing behaviors (particularly the use of prenatal care) as a result of exposure to violence. The positive effect of homicide exposure is heterogeneous across socioeconomic status (SES). It is strong among low-SES women—but only those living in urban areas—and null among the most advantaged women. This variation suggests that behavioral responses to an increase in local homicides depend on a combination of increased vulnerability and access to basic resources that allow women to obtain prenatal care.

Economic contraction and maternal health behaviors during pregnancy in a national sample of U.S. women

PURPOSE

The purpose of this study was to examine associations between maternal exposure to unexpected economic contraction and health behaviors during pregnancy using methods to account for impacts of economic contraction on selection into pregnancy.

METHODS

Data on health behaviors among 7074 pregnancies in the National Longitudinal Survey of Youth 1979 were linked to monthly unemployment rates in maternal state of residence. The study examined associations between exposure to unexpected economic contraction (higher than expected state-level unemployment) during each trimester of pregnancy and maternal smoking, alcohol use, and gestational weight gain using generalized linear models.

RESULTS

Economic contraction was not associated with maternal smoking or gestational weight gain. Associations between economic contraction and maternal alcohol use differed by maternal race-ethnicity and education. Among black-non-Hispanic women, exposures to economic contraction during the first and second trimester of pregnancy were associated with a 42% (95% confidence interval, 1.08, 1.85) and 33% (95% confidence interval, 1.01, 1.74) increased risk of alcohol use, respectively.

CONCLUSIONS

Findings suggest that exposure to extreme economic contraction during pregnancy may be associated with increased use of alcohol with differences by maternal race-ethnicity and educational attainment. Economic contraction was not associated with other maternal pregnancy behaviors.

Low birth weight, small for gestational age and preterm births before and after the economic collapse in Iceland: a population based cohort study

OBJECTIVE

Infants born small for gestational age (SGA) or preterm have increased rates of perinatal morbidity and mortality. Stressful events have been suggested as potential contributors to preterm birth (PB) and low birth weight (LBW). We studied the effect of the 2008 economic collapse in Iceland on the risks of adverse birth outcomes.

STUDY DESIGN

The study population constituted all Icelandic women giving birth to live-born singletons from January 1(st) 2006 to December 31(st) 2009. LBW infants were defined as those weighing <2500 grams at birth, PB infants as those born before 37 weeks of gestation and SGA as those with a birth weight for gestational age more than 2 standard deviations (SD's) below the mean according to the Swedish fetal growth curve. We used logistic regression analysis to estimate odds ratios [OR] and corresponding 95 percent confidence intervals [95% CI] of adverse birth outcomes by exposure to calendar time of the economic collapse, i.e. after October 6(th) 2008.

RESULTS

Compared to the preceding period, we observed an increased adjusted odds in LBW-deliveries following the collapse (aOR = 1.24, 95% CI [1.02, 1.52]), particularly among infants born to mothers younger than 25 years (aOR = 1.85, 95% CI [1.25, 2.72]) and not working mothers (aOR = 1.61, 95% CI [1.10, 2.35]). Similarly, we found a tendency towards higher incidence of SGA-births (aOR = 1.14, 95% CI [0.86, 1.51]) particularly among children born to mothers younger than 25 years (aOR = 1.87, 95% CI [1.09, 3.23]) and not working mothers (aOR = 1.86, 95% CI [1.09, 3.17]). No change in risk of PB was observed. The increase of LBW was most distinct 6-9 months after the collapse.

CONCLUSION

The results suggest an increase in risk of LBW shortly after the collapse of the Icelandic national economy. The increase in LBW seems to be driven by reduced fetal growth rate rather than shorter gestation.

Income gains and very low-weight birth among low-income black mothers in California

We test the hypothesis suggested in the literature that an acute income gain in the form of the earned income tax credit reduces the odds of a very low-weight birth among low-income non-Hispanic black mothers. We apply ecological time series and supplemental individual-level logistic regression methods to monthly birth data from California between 1989 and 1997. Contrary to our hypothesis, the odds of very low-weight birth increases above its expected value two months after mothers typically receive the credit. We discuss our findings in relation to the epidemiologic literature concerned with ambient events during pregnancy and recommend further investigation.

Selection against small males in utero: a test of the Wells hypothesis

BACKGROUND

The argument that women in stressful environments spontaneously abort their least fit fetuses enjoys wide dissemination despite the fact that several of its most intuitive predictions remain untested. The literature includes no tests, for example, of the hypothesis that these mechanisms select against small for gestational age (SGA) males.

METHODS

We apply time-series modeling to 4.9 million California male term births to test the hypothesis that the rate of SGA infants in 1096 weekly birth cohorts varies inversely with labor market contraction, a known stressor of contemporary populations.

RESULTS

We find support for the hypothesis that small size becomes less frequent among term male infants when the labor market contracts.

CONCLUSIONS

Our findings contribute to the evidence supporting selection in utero. They also suggest that research into the association between maternal stress and adverse birth outcomes should acknowledge the possibility that fetal loss may affect findings and their interpretation. Strengths of our analyses include the large number and size of our birth cohorts and our control for autocorrelation. Weaknesses include that we, like nearly all researchers in the field, have no direct measure of fetal loss.