Trends in and characteristics of drug overdose morbidity among pregnant and postpartum individuals in California, 2010-2018.

Fatal drug overdoses among pregnant and postpartum individuals have risen dramatically over the past 10 years. Trends in and characteristics of nonfatal drug overdoses in this population, however, remain unknown, despite the importance of this outcome for maternal and infant health. We used statewide, longitudinally-linked hospital and emergency department administrative claims data from California to characterize the incidence, trends, drug type involvement, and sociodemographic disparities in pregnancy-associated drug overdose between 2010 and 2019. Generalized linear models accounting for multiple deliveries per individual were used to test for trends; descriptive statistics were used for other study analyses. Of California individuals with a live delivery between 2010 and 2018, approximately 0.2% had a pregnancy-associated drug overdose. Nonfatal overdoses were nearly 60 times more common than fatal overdoses. Incidence of overdoses involving stimulants increased in frequency, while incidence of overdoses involving sedative/hypnotic drugs and psychotropic medications decreased in frequency. Risk of overdose was substantially higher among delivering individuals who were young, non-Hispanic Black, Medicaid patients, or who lived in non-metropolitan areas. Ongoing public health surveillance of and clinical interventions to reduce pregnancy-associated nonfatal drug overdose events are critical for prevention efforts.

Are Contraceptive Method Preferences Stable? Measuring Change in the Preferred Method among Kenyan Women.

Contraceptive preferences are important for reproductive outcomes, such as contraceptive continuation and pregnancy. Current approaches to measuring reproductive preferences in population surveys are limited to exploring only fertility preferences and implicitly assume that contracepting people are using a method they want. We know that people change their fertility preferences over the life course as a response to life events, but there is no information about changes in contraceptive preferences, given the limited evidence about the measurement and distribution of contraceptive preferences. In this study, we examined the extent of change in women's contraceptive preferences over one year and identified characteristics associated with this change in Kenya using three rounds of nationally representative longitudinal data. Over one year, 18 percent of contraceptive users and 46 percent of contraceptive nonusers reported changes in their preferred contraceptive. Experiencing a pregnancy or birth and changes in marital status were associated with changes in contraceptive preferences for users and nonusers. We found that contraceptive preferences are dynamic, suggesting that family planning programs should ensure people's access to various methods to respond to women's changing circumstances and preferences.

The pandemic preterm paradox: A test of competing explanations.

Epidemiologists have long argued that side effects of the stress response include preterm birth. Research reports that fear of lethal infection stressed pregnant persons at the outset of the COVID-19 pandemic and that "shutdowns" and "social distancing" impeded access to social support and prenatal care. The decline in preterm births in high-income countries, including the United States (US), during the early months of the pandemic therefore poses a paradox for science. Explanations of this "pandemic preterm paradox" remain untested. We apply time-series modeling to data describing 80 monthly conception cohorts begun in the US from July 2013 through February 2020 to determine which of 3 explanations most parsimoniously explains the paradox. We infer that "prior loss," or the argument that an increase in spontaneous abortions and stillbirths depleted the population of fetuses at risk of preterm birth, best explains data currently available. We describe the implications of these results for public health practice.

Dynamic changes in place-based measures of structural racism and preterm birth in the USA.

BACKGROUND: Structurally racist systems, ideologies and processes generate and reinforce inequities among minoritised racial/ethnic groups. Prior cross-sectional literature finds that place-based structural racism, such as the Index of Concentration at the Extremes (ICE), correlates with higher infant morbidity and mortality. We move beyond cross-sectional approaches and examine whether a decline in place-based structural racism over time coincides with a reduced risk of preterm birth across the USA. METHODS: We used as the outcome count of preterm births overall and among non-Hispanic (NH) black and NH white populations across three epochs (1998-2002, 2006-2010, 2014-2018) in 1160 US counties. For our measure of structural racism, we used ICE race/income county measures from the US Census Bureau. County-level fixed effects Poisson models include a population offset (number of live births) and adjust for epoch indicators, per cent poverty and mean maternal age within counties. RESULTS: An SD increase in ICE (0.11) over time corresponds with a 0.6% reduced risk of preterm birth overall (incidence rate ratio (IRR): 0.994, 95% CI 0.990, 0.998), a 0.6% decrease in preterm risk among NH black births (IRR: 0.994, 95% CI 0.989, 0.999) and a 0.4% decrease among NH white births (IRR: 0.996, 95% CI 0.992, 0.999). CONCLUSIONS: Movement away from county-level concentrated NH black poverty preceded reductions in preterm risk, especially among NH black populations. Our longitudinal design strengthens inference that place-based reductions in structural racism may improve perinatal health. These improvements, however, do not appear sufficient to redress large disparities.

Scarring In Utero: An Attempt to Validate With Data Unconfounded by Migration and Medical Care.

BACKGROUND: "Scarring in utero" posits that populations exposed to injurious stressors yield birth cohorts that live shorter lives than expected from history. This argument implies a positive historical association between period life expectancy (i.e., average age at death in year t) and cohort life expectancy (i.e., average lifespan of persons born in year t). Tests of the argument have not produced consistent results and appear confounded by autocorrelation, migration, and access to medical care. Here we test whether, as predicted by scarring in utero, sex-specific period and cohort life expectancy appear positively related among Swedes born from 1751 through 1800. If scarring has ever influenced longevity, we should detect signals of its effects in these cohorts because, unlike other populations with known life span, they aged in place and unlikely benefitted from increased access to efficacious medical care. METHODS: We use Box-Jenkins methods to control autocorrelation and measure associations. RESULTS: Contrary to the scarring hypothesis, we find an inverse association between period and cohort life expectancy. Our findings imply that, among males, variation in injurious stress on the population predicted changes in cohort life span ranging from a gain of approximately 67 weeks to a loss of about 45 weeks of life and among females from a gain of approximately 68 weeks to a loss of about 38 weeks of life. CONCLUSION: Epidemiologists trying to understand and explain temporal variation in cohort life expectancy should view the scarring argument with greater skepticism than currently found in the literature.

Infant Deaths After Texas' 2021 Ban on Abortion in Early Pregnancy.

Importance: Prior observational research has shown that infants born in states with more abortion restrictions are more likely to die during infancy. It is unclear how recent and more severe abortion bans in the US have impacted infant mortality. Objective: To examine whether Texas Senate Bill 8 (SB8), which banned abortions after embryonic cardiac activity and did not allow exemptions for congenital anomalies, is associated with infant mortality in the state of Texas. Design, Setting, and Participants: This population-based cohort study of all recorded infant deaths from the state of Texas and 28 comparison states used a comparative interrupted time series analysis with an augmented synthetic control approach and national birth certificate data from January 1, 2018, to December 31, 2022, to estimate the difference between the number of observed and expected infant and neonatal deaths and death rates among monthly cohorts exposed to Texas' SB8. Exposure: Deaths in March 2022 were treated as the first cohort exposed to the Texas' SB8 abortion policy because these infants (if born full term) were approximately 10 to 14 weeks' gestation when SB8 went into effect on September 1, 2021. The exposure period was thus March through December 2022. Main Outcomes and Measures: Our outcomes were monthly counts and rates of infant (aged <1 year) and neonatal (aged <28 days) deaths in the exposure period in Texas. In secondary analyses, annual changes in cause-specific infant deaths between 2021 and 2022 in Texas and the rest of the US were examined. Results: Between 2018 and 2022, there were 102 391 infant deaths in the US, with 10 351 of these deaths occurring in the state of Texas. Between 2021 and 2022, infant deaths in Texas increased from 1985 to 2240, or 255 additional deaths. This corresponds to a 12.9% increase, whereas the rest of the US experienced a comparatively lower 1.8% increase. On the basis of the counterfactual analysis that used data from Texas and eligible comparison states, an excess of 216 infant deaths (95% CI, -122 to 554) was observed from March to December 2022, or a 12.7% increase above expectation. At the monthly level, significantly greater-than-expected counts were observed for 4 months between March and December 2022: April, July, September, and October. An analysis of neonatal deaths found somewhat similar patterns, with significantly greater-than-expected neonatal deaths in April and October 2022. Descriptive statistics by cause of death showed that infant deaths attributable to congenital anomalies in 2022 increased more for Texas (22.9% increase) but not the rest of the US (3.1% decrease). Conclusions and Relevance: This study found that Texas' 2021 ban on abortion in early pregnancy was associated with unexpected increases in infant and neonatal deaths in Texas between 2021 and 2022. Congenital anomalies, which are the leading cause of infant death, also increased in Texas but not the rest of the US. Although replication and further analyses are needed to understand the mechanisms behind these findings, the results suggest that restrictive abortion policies may have important unintended consequences in terms of trauma to families and medical cost as a result of increases in infant mortality. These findings are particularly relevant given the recent Dobbs v Jackson Women's Health Organization US Supreme Court decision and subsequent rollbacks of reproductive rights in many US states.

Changes in Racial and Ethnic Inequities in Pregnancy-Associated Death in the United States During the COVID-19 Pandemic.

Objectives. To examine changes in cause-specific pregnancy-associated deaths during the COVID-19 pandemic by race and ethnicity and assess changes in racial and ethnic inequities in pregnancy-associated deaths. Methods. We used US vital statistics mortality data from 2018 to 2021 to identify pregnancy-associated deaths among females aged 15 to 44 years. We calculated crude pregnancy-associated death rates (deaths per 100 000 live births) by year, cause, and race/ethnicity, percent change in death rate, and the inequity (difference) in rate for each racial or ethnic group compared with non-Hispanic White people. Results. The pregnancy-associated death rate for obstetric, drug-related, homicide, and other causes of death increased during 2020, and obstetric deaths continued to increase in 2021. Overall estimates mask 2021 increases in drug-related deaths among Hispanic, non-Hispanic American Indian and Alaska Native (AI/AN), and non-Hispanic Asian people; increases in homicide among most racial and ethnic groups; and increases in suicide among Hispanic, non-Hispanic AI/AN, and non-Hispanic Asian people. Conclusions. We found disproportionate increases in pregnancy-associated deaths from nonobstetric causes among minoritized racial and ethnic groups during the COVID-19 pandemic. (Am J Public Health. 2024;114(7):733-742. https://doi.org/10.2105/AJPH.2024.307651).

Missing Black males among preterm births in the US, 1995 to 2019.

BACKGROUND: In the US, non-Hispanic (NH) Black birthing persons show a two-fold greater risk of fetal death relative to NH white birthing persons. Since males more than females show a greater risk of fetal death, such loss in utero may affect the sex composition of live births born preterm (PTB; <37 weeks gestational age). We examine US birth data from 1995 to 2019 to determine whether the ratio of male to female preterm (i.e., PTB sex ratios) among NH Black births falls below that of NH whites and Hispanics. METHODS: We acquired data on all live births in the US from January 1995 to December 2019. We arrayed 63 million live births into 293 "conception cohort" months of which 2,475,928 NH Black, 5,746,953 NH white, and 2,511,450 Hispanic infants were PTB. We used linear regression methods to identify trend and seasonal patterns in PTB sex ratios. We also examined subgroup differences in PTB sex ratios (e.g., advanced maternal ages, twin gestations, and narrower gestational age ranges). RESULTS: The mean PTB sex ratio for NH Black births over the entire test period (1.06, 95% Confidence Interval [CI]: 1.05, 1.07) is much lower than that for NH white births (1.18, 95% CI: 1.17, 1.19). NH Black PTB sex ratios are especially low for twins and for births to mothers 35 years or older. Only NH white PTB sex ratios show a trend over the test period. CONCLUSIONS: Analysis of over 10 million PTBs reveals a persistently low male PTB frequency among NH Black conception cohorts relative to NH white cohorts. Low PTB sex ratios among NH Black births concentrate among subgroups that show an elevated risk of fetal death. PTB sex ratios may serve as an indicator of racial/ethnic and subgroup differences in fetal death, especially among male gestations.

Variation and correlates of psychosocial wellbeing among nulliparous women with preeclampsia.

OBJECTIVES: To identify classes of psychosocial stressors among women who developed preeclampsia and to evaluate the associations between these classes and correlates of psychosocial wellbeing. STUDY DESIGN: We performed a secondary analysis of women who developed preeclampsia (n = 727) from the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-be (nuMoM2b) cohort (2010-2013). Latent class analysis was used to identify classes of social stressors based on seven psychological and sociocultural indicators. Associations between latent classes and correlates (demographics, health behavior, and health-systems level) were estimated using multinomial logistic regression. MAIN OUTCOME MEASURES: Classes of psychosocial wellbeing. RESULTS: Among women who developed preeclampsia, three classes reflective of psychosocial wellbeing were identified: Class 1: Intermediate Psychosocial Wellbeing (53 %), Class 2: Positive Psychosocial Wellbeing (31 %), Class 3: Negative Psychosocial Wellbeing (16 %). Women in the Negative Psychosocial Wellbeing Class were more likely to have poor sleep and a sedentary lifestyle compared with the Positive and Intermediate Psychosocial Wellbeing Classes. Both the Negative and Intermediate Psychosocial Wellbeing Classes reported concern about their quality of medical care compared with the Positive Psychosocial Wellbeing Class (adjusted odds ratio [aOR]: 6.19, 95 % confidence interval [CI]: 3.37, 11.36 and aOR: 2.19, 95 % CI: 1.31, 3.65, respectively). CONCLUSIONS: Women who develop preeclampsia are heterogenous and experience different intensities of internal and external stressors. Understanding the linkages between psychosocial wellbeing during pregnancy and modifiable behavioral and structural factors may inform future tailored management strategies for preeclampsia and the optimization of maternal postpartum health.

Validity of Birth Certificate Data Compared With Hospital Discharge Data in Reporting Maternal Morbidity and Disparities.

A growing number of studies are using birth certificate data, despite data-quality concerns, to study maternal morbidity and associated disparities. We examined whether conclusions about the incidence of maternal morbidity, including Black-White disparities, differ between birth certificate data and hospitalization data. Using linked birth certificate and hospitalization data from California and Michigan for 2018 (N=543,469), we found that maternal morbidity measures using birth certificate data alone are substantially underreported and have poor validity. Furthermore, the degree of underreporting in birth certificate data differs between Black and White individuals and results in erroneous inferences about disparities. Overall, Black-White disparities were more modest in the birth certificate data compared with the hospitalization data. Birth certificate data alone are inadequate for studies of maternal morbidity and associated racial disparities.

Mortality Due to Hyperglycemic Crises in the US, 1999-2022.

This study analyzes trends in US mortality attributed to both diabetic ketoacidosis and hyperosmolar hyperglycemic state from 1999-2022.

Short Interpregnancy Intervals Among Women Experiencing Homelessness in Colorado.

Importance: Short interpregnancy intervals (SIPIs) are associated with increased risk of adverse maternal and neonatal outcomes. Disparities exist across socioeconomic status, but there is little information on SIPIs among women experiencing homelessness. Objective: To investigate (1) differences in rates and characteristics of SIPIs between women experiencing homelessness and domiciled women, (2) whether the association of homelessness with SIPIs differs across races and ethnicities, and (3) whether the association between SIPIs of less than 6 months (very short interpregnancy interval [VSIPIs]) and maternal and neonatal outcomes differs between participant groups. Design, Setting, and Participants: This cohort study used a Colorado statewide database linking the Colorado All Payer Claims Database, Homeless Management Information System, death records, and infant birth records. Participants included all women who gave birth between January 1, 2016, and December 31, 2021. Data were analyzed from September 1, 2022, to May 10, 2023. Exposures: Homelessness and race and ethnicity. Main Outcomes and Measures: The primary outcome consisted of SIPI, a binary variable indicating whether the interval between delivery and conception of the subsequent pregnancy was shorter than 18 months. The association of VSIPI with maternal and neonatal outcomes was also tested. Results: A total of 77 494 women (mean [SD] age, 30.7 [5.3] years) were included in the analyses, of whom 636 (0.8%) were women experiencing homelessness. The mean (SD) age was 29.5 (5.4) years for women experiencing homelessness and 30.7 (5.3) years for domiciled women. In terms of race and ethnicity, 39.3% were Hispanic, 7.3% were non-Hispanic Black, and 48.4% were non-Hispanic White. Associations between homelessness and higher odds of SIPI (adjusted odds ratio [AOR], 1.23 [95% CI, 1.04-1.46]) were found. Smaller associations between homelessness and SIPI were found among non-Hispanic Black (AOR, 0.59 [95% CI, 0.37-0.96]) and non-Hispanic White (AOR, 0.57 [95% CI, 0.39-0.84]) women compared with Hispanic women. A greater association of VSIPI with emergency department visits and low birth weight was found among women experiencing homelessness compared with domiciled women, although no significant differences were detected. Conclusions and Relevance: In this cohort study of women who gave birth from 2016 to 2021, an association between homelessness and higher odds of SIPIs was found. These findings highlight the importance of conception management among women experiencing homelessness. Racial and ethnic disparities should be considered when designing interventions.

Change in Epidemiology of Creutzfeldt-Jakob Disease in the US, 2007-2020.

This cross-sectional study uses Centers for Disease Control and Prevention multiple cause of death data to examine recent US trends in Creutzfeldt-Jakob disease.

Pregnancy and pregnancy intention after experiencing infertility: A longitudinal study of women in Malawi.

BACKGROUND: Infertility is a common experience among individuals and couples. Infertility may resolve without intervention, but little is known about pregnancy intentions and incidence of pregnancy following infertility, particularly in low-resource settings. METHODS: Data come from UTHA, a longitudinal cohort study in Central Malawi, with baseline and follow up surveys conducted from 2014-2019 (N = 1,030 reproductive-aged women). We assessed bivariable and multivariable relationships between reported infertility at baseline and subsequent pregnancy and retrospective pregnancy intentions. Pregnancy intention was measured with the London Measure of Unplanned Pregnancy (LMUP), a scale validated in Malawi (Range = 0-12). RESULTS: Approximately 20% of the sample reported that they had ever experienced infertility (tried to become pregnant for at least two years without conceiving in that time) at baseline. The proportion of women who reported a new pregnancy during the follow up period (mean = 4.3 years) was the same (65%) for women who had and had not experienced infertility. Among women who became pregnant, levels of pregnancy intendedness were similar between women who had and had not experienced infertility. Prospective desire for a/another child at baseline was associated with subsequent pregnancy (AOR: 1.59; 95%CI: 1.06-2.39) and was also associated with higher levels of pregnancy intendedness measured retrospectively (LMUP of 9.4 vs. 8.4). CONCLUSIONS: Experienced infertility was not associated with differential odds of having a subsequent pregnancy or the intendedness of a subsequent pregnancy. Thus, women who have experienced infertility should be included in family planning programs and research to support all women in achieving their reproductive goals.

Casino-based cash transfers and fertility among the Eastern Band of Cherokee Indians in North Carolina: A time-series analysis.

Fertility decline remains a key concern among high-income countries. Prior research indicates that income supplementation through unconditional cash transfers (UCT) may correspond with increased fertility. We examine whether a casino-based UCT, in the form of per capita (percap) payments to members of the Eastern Band of Cherokee Indians (EBCI) corresponds with an acute increase in fertility. We use North Carolina vital statistics datasets from 1990 to 2006 and apply time-series analysis methods to examine the relation between specific months of percap payments (exposure) and monthly number of conceptions that result in live births (outcome) among the EBCI. We control for autocorrelation and monthly counts of births (arrayed by conception cohorts) among white women (ineligible for UCT receipt) in the study region. Results indicate an increase in conceptions that result in live births at 1 and 3 months after percap receipt among EBCI women aged ≥20 years (exposure month lag 1 coefficient = 1.74, p = 0.03; exposure month lag 3 coefficient = 1.60, p = 0.04). Exploratory analyses indicate that the observed fertility increase concentrates among primiparae EBCI women. We do not find any association between percap payment timing and births to EBCI women aged <20 years.

Reproductive outcomes following contraceptive discontinuation for method-related reasons: An analysis of 49 Demographic and Health Surveys.

Contraceptive discontinuation for method-related reasons is a common experience in low- and middle-income countries (LMICs) and may heighten women's risk of unintended pregnancy. Few studies have provided a comprehensive assessment of reproductive outcomes following contraceptive discontinuation in LMICs over the last decade. Using cross-sectional data from 49 Demographic and Health Surveys, we applied competing risks estimation to calculate monthly probabilities of contraceptive resumption and pregnancy over a 12-month period among pooled, regional, and country-specific samples of women who discontinued contraception for method-related reasons (corresponding to 174,726 episodes of discontinuation). We also examined the pregnancy intention status of births/current pregnancies among those who became pregnant in the 12 months following contraceptive discontinuation for method-related reasons. In the pooled sample, the three-month probability of pregnancy and resumption of contraceptive use was 12% and 47%, respectively; by 12 months these probabilities increased to 22% and 55%, respectively. Country-specific analyses show that the probabilities of resuming contraception by three months ranged from 15% in Liberia, Mali, and Sierra Leone to 85% in Bangladesh. On average, the majority of pregnancies/births that occured following discontinuation for method-related reasons were subsequently reported as unintended. However, reports varied depending on when women became pregnant within the 12 months following discontinuation. Our findings suggest the need for more nuanced measures of contraceptive use dynamics-including measures that distinguish between women who resume use of contraception from women who remain at risk of pregnancy in the short period after discontinuation-to better inform specific policies and interventions, particularly aimed at those who remain at risk of pregnancy.

Environmental attitudes and fertility desires among US adolescents from 2005-2019.

Objective: This Brief Report examines links between environmental attitudes and fertility desires over time in the U.S. Background: To understand fertility decision making, it is important to identify factors that influence fertility desires. Concerns about environmental problems may be associated with lower desired fertility, especially in recent cohorts transitioning to adulthood. Youth may feel that having one less child can reduce their "carbon footprint" or may be unwilling to bring children into an uncertain and difficult future due to climate change. Method: Data are from 12th graders in the Monitoring the Future Study (2005-2019; N=34,104). Regression is used to examine the relationship between number of children wanted and agreement that the government should deal with environmental problems even if it means paying more taxes. Results: Those who endorsed that government should deal with environmental problems reported lower average fertility desires than those who did not. The association was driven by a decreased desire for large families (four or more children) rather than normatively sized families (two-three children). Political identity and religiosity attenuated but did not explain the association. There was some evidence of stronger associations in 2017-2019. Conclusion: Evidence showed associations between environmental attitudes and childbearing preferences that may have strengthened over time. Implications: Environmental attitudes may be a factor in the recent decline in youth's fertility desires and could have consequences for future fertility.

Disparities in preterm birth following the July 1995 Chicago heat wave.

PURPOSE: To evaluate if changes in preterm birth (PTB, <37 weeks of gestation) incidence differed between non-Hispanic (NH) Black and NH white births following the July 1995 Chicago heat wave-among the most severe U.S. heat waves since 1950. METHODS: We used an ecologic study design. We obtained birth data from January 1990-December 1996 from the National Vital Statistics File to calculate the mean monthly PTB incidence in Chicago's Cook County, Illinois. Births between July 1995 and February 1996 were potentially exposed to the heat wave in utero. We generated time series models for NH Black and NH white births, which incorporated synthetic controls of Cook County based on unexposed counties. We ran a secondary analysis considering socioeconomic status (SES). RESULTS: From 1990-1996, the mean monthly PTB incidence among NH Black births was 18.6% compared to 7.8% among NH white births. The mean monthly PTB incidence among NH Black births from August 1995-January 1996 was 16.7% higher than expected (three additional PTBs per 100 live births per month [95% confidence interval (CI): 1, 5]). A similar increase occurred among low-SES NH Black births. No increase appeared among NH white births. CONCLUSIONS: Severe heat waves may increase racial disparities in PTB incidence.

A novel indicator of selection in utero.

Background and objectives: Selection in utero predicts that population stressors raise the standard for how quickly fetuses must grow to avoid spontaneous abortion. Tests of this prediction must use indirect indicators of fetal loss in birth cohorts because vital statistics systems typically register fetal deaths at the 20th week of gestation or later, well after most have occurred. We argue that tests of selection in utero would make greater progress if researchers adopted an indicator of selection against slow-growing fetuses that followed from theory, allowed sex-specific tests and used readily available data. We propose such an indicator and assess its validity as a dependent variable by comparing its values among monthly birth cohorts before, and during, the first 10 months of the COVID-19 pandemic in Sweden. Methodology: We apply Box-Jenkins methods to 50 pre-pandemic birth cohorts (i.e., December 2016 through January 2020) and use the resulting transfer functions to predict counterfactual values in our suggested indicator for selection for ten subsequent birth cohorts beginning in February 2020. We then plot all 60 residual values as well as their 95% detection interval. If birth cohorts in gestation at the onset of the pandemic lost more slow-growing fetuses than expected from history, more than one of the last 10 (i.e. pandemic-exposed) residuals would fall below the detection interval. Results: Four of the last 10 residuals of our indicator for males and for females fell below the 95% detection interval. Conclusions and implications: Consistent with selection in utero, Swedish birth cohorts in gestation at the outset of the COVID-19 pandemic included fewer than expected infants who grew slowly in utero.