Association of Special Supplemental Nutrition Program for Women, Infants, and Children With Preterm Birth and Infant Mortality | Neonatology | JAMA Network Open | JAMA Network
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Figure 1.  Proportion of Expectant Mothers Covered by Medicaid Who Received Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) Benefits During Pregnancy, 2011-2017
Proportion of Expectant Mothers Covered by Medicaid Who Received Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) Benefits During Pregnancy, 2011-2017
Figure 2.  Association of Preterm Birth and Infant Mortality Rate With Receipt of Women, Infants, and Children (WIC) Benefits During Pregnancy Among Expectant Mothers Covered by Medicaid, 2011-2017
Association of Preterm Birth and Infant Mortality Rate With Receipt of Women, Infants, and Children (WIC) Benefits During Pregnancy Among Expectant Mothers Covered by Medicaid, 2011-2017
Table 1.  Characteristics of Expectant Mothers Whose Births Occurred in US States That Adopted the 2003 Revision of the US Standard Certificate of Live Birth, 2011-2017a
Characteristics of Expectant Mothers Whose Births Occurred in US States That Adopted the 2003 Revision of the US Standard Certificate of Live Birth, 2011-2017a
Table 2.  Multivariable Ordinal Regression Results for Preterm Birth and Logistic Regression for Infant Mortality Among Expectant Mothers Covered by Medicaid During Pregnancy, 2011-2017
Multivariable Ordinal Regression Results for Preterm Birth and Logistic Regression for Infant Mortality Among Expectant Mothers Covered by Medicaid During Pregnancy, 2011-2017
Table 3.  Estimated Probability of Preterm Birth and Infant Mortality Rate Among Expectant Mothers Covered by Medicaid Who Did and Did Not Receive WIC Benefits During Pregnancya
Estimated Probability of Preterm Birth and Infant Mortality Rate Among Expectant Mothers Covered by Medicaid Who Did and Did Not Receive WIC Benefits During Pregnancya
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    1 Comment for this article
    Benefits of food supplements
    Frederick Rivara, MD, MPH | University of Washington
    This week saw a reduction in the number of people in the US eligible for food stamps. WIC is another program to reduce poverty and poor nutrition and has been very successful. This article shows that it is successful in reducing the risk pf prematurity and thus lowering infant mortality. It is further evidence that programs started during the war on poverty can have lasting effects.
    CONFLICT OF INTEREST: Editor in Chief, JAMA Network Open
    Original Investigation
    Public Health
    December 4, 2019

    妇女、婴儿及儿童特别补充营养计划与早产儿和婴儿死亡率的关联性

    Author Affiliations
    • 1Department of Health Behavior, University of North Carolina, Chapel Hill
    • 2Department of Community Health Sciences, UCLA (University of California, Los Angeles)
    • 3California Center for Population Research, Los Angeles
    JAMA Netw Open. 2019;2(12):e1916722. doi:10.1001/jamanetworkopen.2019.16722
    关键点 español English

    问题  在美国的低收入孕妇中,孕期享有妇女、婴儿及儿童特别补充营养计划福利是否与早产儿和婴儿死亡率相关?

    结果  这项队列研究涉及 11,148,261 名在 2011 年至 2017 年参加医疗保险的孕妇。研究表明,孕期还享受妇女、婴儿及儿童福利的比例从 2011 年的 79.3% 降至 2017 年的 67.9%。不过,在低收入女性中,享受这些福利与早产儿和婴儿死亡率的下降有关。

    意义  这项研究的调查结果表明,在低收入孕妇中,提高对补充营养福利的重视程度,可以减少早产儿和婴儿死亡率负担。而在美国,低收入孕妇占所有孕妇的 42.9%。

    Abstract

    Importance  Nearly 4 in 10 expectant mothers in the United States received Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) benefits during pregnancy between 2011 and 2017. Despite public support for the program, empirical evidence of the success of the program varies substantially.

    Objective  To assess the association of WIC program participation during pregnancy by low-income expectant mothers covered by Medicaid with infant mortality by gestational age at birth and by maternal race/ethnicity in comparison with their counterparts who did not receive WIC benefits.

    Design, Setting, and Participants  This cohort study obtained data from January 1, 2011, to December 31, 2017, from US live birth certificates. Data were from 11 148 261 expectant mothers who delivered live births in states that have implemented the 2003 revision of the US live birth certificate and whose insurance coverage and receipt of WIC benefits were recorded on the birth certificates. Data analysis was performed from June 2019 to October 2019.

    Exposures  Receipt of WIC benefits during pregnancy.

    Main Outcomes and Measures  The first outcome was gestational age at birth: extremely preterm (<28 weeks), very preterm (28-32 weeks), moderate-to-late preterm (32-37 weeks), and normal term (≥37 weeks) births. The second outcome was death within the first year of life.

    Results  Among the 11 148 261 expectant mothers who delivered live births between 2011 and 2017 and were covered by Medicaid during pregnancy, the modal age at delivery was 20 to 24 years, the predominant race/ethnicity was non-Hispanic white (4 257 790 [38.2%]), and 8 145 770 (73.1%) received WIC benefits during pregnancy. The proportion of expectant mothers covered by Medicaid who also received WIC benefits decreased from 2011 to 2017 (79.3% to 67.9%; P < .001). The odds of preterm birth compared with normal term birth were lower among expectant mothers covered by Medicaid who received WIC benefits during pregnancy compared with their counterparts who did not receive WIC benefits during pregnancy (adjusted proportional odds ratio, 0.87; 95% CI, 0.86-0.87). The odds of mortality within 1 year of birth were lower for infants whose mothers were covered by Medicaid and received WIC benefits during pregnancy compared with those who did not receive WIC benefits during pregnancy (adjusted odds ratio, 0.84; 95% CI, 0.83-0.86).

    Conclusions and Relevance  This study found that receipt of WIC benefits among expectant mothers with Medicaid coverage was associated with lower risk of preterm birth and infant mortality.

    Introduction

    In 2018, the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) provided approximately 700 000 expectant mothers with checks or vouchers to purchase food to supplement their diets with specific nutrients (the mean monthly benefit was $40.96).1 Although the WIC program receives widespread public support, empirical evidence of the success of the program varies substantially.2,3 Numerous studies conclude that participation in the WIC program is associated with improved birth outcomes, such as higher birth weight, lower likelihood of neonatal intensive care unit admission, and lower Medicaid costs for newborns and mothers.4-11

    Other studies question these conclusions of success and commonly note 2 possible limitations.12-15 First, some low-income women may be more able to participate in the WIC program because they are comparatively healthier or more well resourced compared with other low-income women (selection bias). Second, women with longer pregnancies may experience better birth outcomes because of their greater gestational period rather than because of receipt of WIC benefits (gestational age bias). Accounting for these possible biases, some studies found a much lower or no association between WIC and gestational age, birth weight, and infant mortality. In addition, other studies found WIC participation to be associated with improved birth outcomes for low-income minority women, but either less or no association was found for low-income white women.16,17

    This national-based cohort study addresses this controversy by assessing the association of WIC participation with infant mortality (accounting for gestational age at birth) using data from 11 million birth certificates with 1-year mortality follow-up. We also estimate the association of WIC participation with infant mortality by maternal race/ethnicity. We believe the study provides timely and contemporary empirical evidence to policy makers about the WIC program, which, like other safety net programs, could face possibly substantial budget cuts in the foreseeable future.18

    Methods
    Data

    This cohort study analyzed US birth certificate data from January 1, 2011, to December 31, 2017, collected by the National Center for Health Statistics as part of the National Vital Statistics System.19,20 The Dartmouth College Committee for the Protection of Human Subjects determined that institutional review board review and informed consent were not required for the present study because the regulatory definition of human participant research did not apply. The data used were deidentified and publicly available. This study followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) reporting guideline.

    The 2003 revision of the US Standard Certificate of Live Birth ascertained insurance coverage and receipt of WIC benefits during pregnancy. In 2011, 36 states and the District of Columbia—accounting for 83% of all US births in 2011—had implemented the 2003 revision.21 By 2016, all 50 states and the District of Columbia had implemented this revision.22 This study used data from 25 263 716 expectant mothers who had live births in states that followed the 2003 rule and for whom the type of insurance coverage and receipt of WIC benefits were recorded on the birth certificate (representing 91.5% of all live births between 2011 and 2017; eTable 1 in the Supplement).

    Outcomes

    The first outcome was gestational age at birth, including extremely preterm (<28 weeks), very preterm (28-32 weeks), moderate-to-late preterm (32-37 weeks), and normal (≥37 weeks) births. The second outcome was death within the first year of life among infants who were born alive.

    Primary Variable of Interest and Covariates

    The primary variable of interest was receipt of WIC benefits during pregnancy. Sociodemographic characteristics of expectant mothers included their age at delivery (<15, 15-19, through 50-54 years), race/ethnicity (Hispanic, non-Hispanic black, non-Hispanic white, or non-Hispanic other race/ethnicity), educational attainment (<high school graduate, high school graduate, or at least some college), marital status (married or unmarried), and source of payment for the delivery (Medicaid, private insurance, self-pay/uninsured, or other). We considered source of payment for the delivery as the type of health insurance coverage for the expectant mother. Pregnancy history included lifetime number of pregnancies (gravida), births of viable offspring (para), and abortions (aborta). Receipt of prenatal care was categorized as either none or at least some prenatal care during pregnancy. Obstetric complications included prepregnancy diabetes, gestational diabetes, prepregnancy hypertension, gestational hypertension, and hypertension eclampsia. Method of delivery and final route included spontaneous, forceps, vacuum, and cesarean. Smoking frequency was categorized as 0 or 1 or more cigarettes per day 3 months before pregnancy and 0 or 1 or more cigarettes per day during pregnancy. The proportion of births with missing data on any of these covariates ranged between 0.0% and 3.5% (eTable 2 in the Supplement).

    Statistical Analysis

    We performed a multistep analysis. First, we assessed the distribution of sociodemographic characteristics and pregnancy history for expectant mothers who were covered by Medicaid and delivered live births in US states that ascertained whether women had insurance coverage and received WIC benefits during pregnancy. Second, we calculated the annual proportion of expectant mothers (1) whose births were covered by Medicaid, (2) who received WIC benefits during pregnancy, and (3) whose births were covered by Medicaid and who also received WIC benefits during pregnancy. We tested for time trends by fitting a least-squares regression line of each proportion against year.

    Third, we calculated the proportion of extremely, very, and moderate-to-late preterm births among expectant mothers covered by Medicaid who either did or did not receive WIC benefits during pregnancy. We assessed the differences between each pair of proportions using Pearson χ2 test with Yates continuity correction. Fourth, we calculated the infant mortality rate among expectant mothers covered by Medicaid who either did or did not receive WIC benefits during pregnancy, and we similarly assessed the difference between these proportions. The infant mortality rate equaled the number of deaths within the first year of life among infants who were born alive per 1000 live births.23

    Fifth, we fit a multivariable ordinal logistic regression model to identify the association between receipt of WIC benefits during pregnancy and preterm birth among expectant mothers covered by Medicaid. The outcome of the model was gestational age at birth (extremely preterm, very preterm, moderate-to-late preterm, and normal term births). Other covariates included year of birth, sociodemographic characteristics (age at delivery, race/ethnicity, educational attainment, and marital status), pregnancy history (GPA), receipt of prenatal care, clinical risk factors, and cigarette smoking before and during pregnancy.

    Sixth, we fit a multivariable logistic regression model to identify the association between receipt of WIC benefits during pregnancy and infant mortality among expectant mothers covered by Medicaid. The outcome of the model was infant mortality, and the covariates were identical to the first model as well as the method of delivery and gestational age category.

    Seventh, to illustrate the population-level implication of receiving WIC benefits during pregnancy, we estimated the probabilities of extremely, very, and moderate-to-late premature births and infant mortality according to the results of the regression models in steps 5 and 6.24 We considered a common subpopulation of expectant mothers with the following characteristics: primigravid and nulliparous (gravida 1, para 1), aged 25 to 29 years, non-Hispanic white, married, and nonsmoker before and during pregnancy. We varied receipt of WIC benefits during pregnancy.

    Eighth, we fit similar regression models as those in steps 5 and 6 and included the interaction of race/ethnicity and receipt of WIC benefits during pregnancy to assess whether the associations differed by race/ethnicity. We also fit a multivariable logistic regression model to evaluate the association between receipt of WIC benefits during pregnancy and spontaneous birth compared with indicated birth by cesarean delivery among expectant mothers covered by Medicaid who delivered preterm births.

    Listwise deletion was used to remove cases with missing data in all regression models. Throughout the analysis, statistical significance was assessed at 2-sided P < .05. All statistical calculations were done with R, version 3.6.1 (R Project for Statistical Analysis). We conducted data analysis from June 2019 to October 2019.

    Results
    Study Sample

    The number of expectant mothers covered by Medicaid during pregnancy between 2011 and 2017 totaled 11 148 261 (42.9% of all expectant mothers in the United States; Table 1). Among expectant mothers covered by Medicaid, the modal age at delivery was 20 to 24 years, and 4 257 790 (38.2%) of expectant mothers were non-Hispanic white, 3 627 356 (32.5%) were Hispanic, and 2 458 740 (22.1%) were non-Hispanic black. Most expectant mothers were high school graduates (4 130 571 [37.1%]) or had at least some college education (3 957 690 [35.5%]) and were unmarried (7 173 141 [64.3%]). More than 7 in 10 (8 145 770 [73.1%]) received WIC benefits during pregnancy, and more than 9 in 10 (10 559 749 [94.7%]) received at least some prenatal care during pregnancy.

    Medicaid Coverage and Receipt of WIC Benefits During Pregnancy

    The proportion of expectant mothers covered by Medicaid decreased from 2011 to 2017 (44.0% to 43.0%; P = .01; Figure 1A). The proportion of expectant mothers who received WIC benefits during pregnancy decreased from 2011 to 2017 (47.3% to 38.1%; P < .001). The proportion of expectant mothers covered by Medicaid who also received WIC benefits during pregnancy decreased from 2011 to 2017 (79.3% to 67.9%; P < .001; Figure 1B).

    Preterm Birth and Infant Mortality Among Expectant Mothers Covered by Medicaid

    Among expectant mothers covered by Medicaid, the prevalence of preterm birth was lower among those who received WIC benefits during pregnancy compared with those who did not. For example, the prevalence of extremely premature birth was 56 558 (0.7%) among those who received WIC benefits during pregnancy and 34 800 (1.2%) among those who did not (P < .001; Figure 2A). The prevalence of very premature birth was 105 448 (1.3%) among those who received WIC benefits during pregnancy and 46 873 (1.7%) among those who did not (P < .001). The prevalence of moderate-to-late premature birth was 853 076 (10.5%) among those who received WIC benefits during pregnancy and 316 155 (11.2%) among those who did not (P < .001). The infant mortality rate was 5.2 deaths per 1000 live births among those who received WIC benefits during pregnancy and 8.2 deaths per 1000 live births among those who did not (a 36.6% relative risk reduction).

    Regression Analyses

    Univariable regressions identified statistically significant associations between receipt of WIC benefits during pregnancy and preterm birth and infant mortality among expectant mothers covered by Medicaid (eTable 3 in the Supplement). Based on the multivariable regressions, the odds of preterm birth compared with normal gestational age birth were lower for expectant mothers who were covered by Medicaid and received WIC benefits during pregnancy compared with those who did not receive WIC benefits during pregnancy (adjusted proportional odds ratio [OR], 0.87; 95% CI, 0.86-0.87), controlling for sociodemographic characteristics, clinical risk factors, receipt of prenatal care, and maternal smoking (Table 2). The adjusted odds of infant mortality were lower for mothers who received WIC benefits during pregnancy compared with those who did not (adjusted OR [aOR], 0.84; 95% CI, 0.83-0.86), controlling for the aforementioned covariates and gestational age at birth.

    Based on the multivariable regression models, receipt of WIC benefits was associated with lower absolute and relative risks of preterm birth and infant mortality among expectant mothers covered by Medicaid (Table 3). For example, the probability of moderate-to-late premature birth, the most common category of preterm birth, was 6.40% (95% CI, 6.35%-6.45%) among the 25- to 29-year-old non-Hispanic white primigravid and nulliparous expectant mothers who did not smoke before or during pregnancy, were covered by Medicaid, and did not receive WIC benefits during pregnancy. The probability was 5.47% (95% CI, 5.43%-5.52%) among the same subpopulation of expectant mothers who instead received WIC benefits during pregnancy. This difference corresponded to an absolute risk reduction of 0.93 percentage point (95% CI, 0.90-0.95) and a relative risk reduction of 16.90% (95% CI, 16.45%-17.39%).

    For this same subpopulation of expectant mothers, the mortality rate of infants under the moderate-to-late premature birth category was 7.09 deaths per 1000 live births (95% CI, 6.79-7.44) among mothers who did not receive WIC benefits during pregnancy, and the mortality rate was 5.98 deaths per 1000 live births (95% CI, 5.72-6.26) among mothers who received WIC benefits during pregnancy. This difference corresponded to an absolute risk reduction of 1.12 deaths per 1000 live births (95% CI, 0.99-1.24) and a relative risk reduction of 18.66% (95% CI, 16.59%-20.77%).

    Association of WIC, Preterm Birth, and Infant Mortality With Race/Ethnicity

    The odds of preterm birth compared with normal gestational age birth were lower for non-Hispanic white (aOR, 0.90; 95% CI, 0.89-0.91), non-Hispanic black (aOR, 0.88; 95% CI, 0.87-0.89), and Hispanic (aOR, 0.91; 95% CI, 0.90-0.92) expectant mothers covered by Medicaid who received WIC benefits during pregnancy compared with their counterparts who did not receive WIC benefits during pregnancy (eTable 4 in the Supplement). Similarly, the odds of infant mortality were lower for non-Hispanic white (aOR, 0.90; 95% CI, 0.87-0.93), non-Hispanic black (aOR, 0.91; 95% CI, 0.87-0.95), and Hispanic (aOR, 0.85; 95% CI, 0.81-0.90) expectant mothers covered by Medicaid who received WIC benefits during pregnancy compared with their counterparts who did not receive WIC benefits during pregnancy.

    Spontaneous Preterm Birth

    The odds of spontaneous birth compared with indicated birth by cesarean delivery were lower for expectant mothers covered by Medicaid who received WIC benefits during pregnancy and delivered prematurely compared with their counterparts who did not receive WIC benefits during pregnancy (aOR, 0.95; 95% CI, 0.95-0.96; eTable 5 in the Supplement).

    Discussion

    Three central findings emerged from this national cohort study of prenatal WIC participation. First, the proportion of low-income expectant mothers (ie, covered by Medicaid) who also received WIC benefits decreased substantially over time. Second, receipt of WIC benefits during pregnancy was associated with reduced odds of preterm birth and infant mortality. Third, the magnitude of these associations was approximately equal among low-income non-Hispanic black, Hispanic, and non-Hispanic white women.

    These findings are consistent with those of a large body of research that found participation in the WIC program was associated with improved birth outcomes.5,25-28 This study adds to the existing literature by providing a contemporary estimate of the associations between WIC and preterm birth and between WIC and infant mortality.

    Participation in WIC may lower the likelihood of preterm birth and reduce gestational age–specific infant mortality through several possible biological mechanisms. First, the food supplementation enabled by WIC participation is associated with higher overall and protein-specific caloric intake, both of which are associated with improved fetal growth and increased birth weight.29,30 Second, WIC participation during pregnancy is associated with increased vitamin D intake, which may lower the risk of pregnancy-induced hypertension and preeclampsia (a major cause of fetal mortality).28,31 Similarly, WIC participation during pregnancy is associated with greater maternal iron intake, which may increase birth weight for gestational age.28,32 Third, the WIC program encourages breastfeeding by providing guidance, counseling, and breast pumps.33 Breastfeeding is associated with reduced risk of postneonatal death (death between 28 days and 1 year after birth).34

    This study reaches substantively different conclusions from those of several studies that found no or little association between WIC benefits and key birth outcomes. For example, Foster et al13 assessed the association between WIC participation and 6 birth outcomes (eg, preterm birth) and found no significant implications of the WIC program. However, assessment of WIC participation was based on maternal recall; for some participants, pregnancy occurred years or decades before they were surveyed. The present study was based on maternal recall of WIC participation at the time of delivery and was likely subject to less recall bias. Joyce et al12 noted that gestational age bias could have led to overestimated associations between WIC and birth outcomes. We accounted for gestational age bias and found reduced odds of infant mortality within each gestational age category.

    Another potential limitation of studies on WIC and birth outcomes is selection bias. Some low-income women may have been more able to enroll in the WIC program and maintain and renew their benefits compared with other low-income women.15 Bitler and Currie5 argued that low-income women who enrolled in the program were more disadvantaged than their counterparts who did not enroll; however, the program was still associated with improved birth outcomes.3 Thus, any selection bias would lead to a conservative estimate of the association.5 We found that this pattern of relative disadvantage may persist; in the present study, low-income women enrolled in the WIC program during pregnancy had lower educational attainment compared with their counterparts who did not enroll in the program.

    Previous research found that the association between WIC and birth outcomes may not be equal across race/ethnicity.16,17 For example, between 2005 and 2008, Khanani et al17 assessed the association between WIC participation and infant mortality in a single Ohio county (Hamilton County, which includes the Cincinnati area) and found that the program was not associated with lower infant mortality among low-income white women. However, results from Hamilton County may not be generalizable to the rest of the United States. For example, WIC participation rates among pregnant women were lower (eg, 41% in Hamilton County vs 54% nationally), and infant mortality rates were higher (eg, 19.3 deaths per 1000 live births in Hamilton County vs 13.3 deaths per 1000 live births nationally).17,35 The present nationwide study found that receipt of WIC benefits during pregnancy was associated with lower infant mortality accounting for gestational age at birth, and this association was approximately equal in magnitude across race/ethnicity.

    The proportion of WIC-eligible pregnant women who actually received benefits decreased from approximately 59% in 2009 to 50% in 2016.36 This decline may be associated in part with logistical barriers faced by low-income expectant mothers to enrolling and fully participating in the program.37 First, some women have reported long wait times for receiving benefits at WIC offices as a key barrier to program participation.38 Second, once women receive their benefits in the form of checks or vouchers, they may experience embarrassment or negative interactions with cashiers or other customers at stores when redeeming their benefits.39 Third, participants may face limited selection in shopping because some retailers may not carry WIC-eligible foods and products in allowable sizes and quantities.40 It is not known, however, whether these structural barriers have worsened over time. Nonetheless, the cumulative implications of these barriers may lead some low-income women to forgo WIC benefits in favor of Supplemental Nutrition Assistance Program benefits. The Supplemental Nutrition Assistance Program benefits are more generous (eg, $126 per person per month) and disbursed through an electronic benefits transfer card rather than as a check or voucher (as with WIC).41

    Pregnant women eligible for Medicaid are automatically eligible to receive WIC benefits. The Patient Protection and Affordable Care Act of 2010 enabled states to raise the income eligibility limit by providing federal government cost sharing to offset the cost of additional Medicaid beneficiaries.42 To date, 35 states and the District of Columbia have expanded Medicaid by raising the income eligibility threshold.43 The income eligibility threshold varies by state: 17 states set eligibility up to 199% of the federal poverty level (FPL), 22 states set eligibility between 200% and 249% of the FPL, and 12 states and the District of Columbia set eligibility at ≥250% of the FPL; in 2019, the FPL was $21 330 for a family of 3.44 Actual WIC participation did not necessarily increase in states that raised the income eligibility for Medicaid after enactment of the Patient Protection and Affordable Care Act.45 Overall, national WIC participation among eligible pregnant women decreased from 56.8% in 2010 to 50.3% in 2016 despite Medicaid expansion during this period.46 California, for example, expanded Medicaid eligibility in 2010 and set income eligibility for pregnant women at 213% of the FPL. However, the number of pregnant women who received WIC benefits decreased from 187 000 in 2010 to 152 000 in 2016.1 Public health campaigns to increase enrollment and greater federal funding could ensure that all expectant mothers with low income or at risk for poor nutrition receive WIC benefits throughout their pregnancy.

    Strengths and Limitations

    This study has several strengths. First, it used more than 11 million birth certificate records with linked mortality follow-up for 1 year. Second, it addressed a possible limitation of gestational age bias association with WIC and birth outcomes by directly assessing patterns in infant mortality and accounting for gestational age at birth.

    This study also has several limitations. First, states adopted the 2003 revision of the US Standard Certificate of Live Birth, which ascertains health insurance coverage and receipt of WIC benefits for women during pregnancy, in different years. The temporal analysis based on this revision included 83% of all live births in 2011, 90% of all live births in 2014, and 100% of all live births in 2016 and 2017. Second, birth certificate data did not identify the frequency of WIC benefits use during pregnancy. Some expectant mothers may not have been able to redeem WIC benefits every month because of logistical barriers. Thus, we may conservatively estimate the association between WIC benefits and gestational age and infant mortality. Third, this study focused on live births and excluded pregnancies that resulted in miscarriage and stillbirth. Participation in the WIC program may reduce the incidence of these adverse outcomes among high-risk women in part through increased nutrition and prenatal visits.47

    Conclusions

    This cohort study found that receipt of WIC benefits during pregnancy was associated with lower preterm birth and infant mortality for low-income women. Promoting WIC enrollment through public health campaigns and increasing federal funding for the program could raise the number of expectant mothers with low income or at risk for poor nutrition receiving the benefits throughout their pregnancy.

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    Article Information

    Accepted for Publication: October 14, 2019.

    Published: December 4, 2019. doi:10.1001/jamanetworkopen.2019.16722

    Open Access: This is an open access article distributed under the terms of the CC-BY License. © 2019 Soneji S et al. JAMA Network Open.

    Corresponding Author: Samir Soneji, PhD, Department of Health Behavior, University of North Carolina, Rosenau Hall, 135 Dauer Dr, Chapel Hill, NC 27599 (sonejis@email.unc.edu).

    Author Contributions: Dr Soneji had full access to all of the data in the study, and Drs Soneji and Beltrán-Sánchez take responsibility for the integrity of the data and the accuracy of the data analysis.

    Concept and design: Both authors.

    Acquisition, analysis, or interpretation of data: Both authors.

    Drafting of the manuscript: Both authors.

    Critical revision of the manuscript for important intellectual content: Both authors.

    Statistical analysis: Both authors.

    Administrative, technical, or material support: Both authors.

    Supervision: Beltrán-Sánchez.

    Conflict of Interest Disclosures: None reported.

    Funding/Support: This study was supported by grant P2C-HD041022 to the California Center for Population Research, University of California, Los Angeles, from the National Institute of Child Health and Human Development.

    Role of the Funder/Sponsor: The funder had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

    Additional Contributions: Valerie Lewis, PhD, University of North Carolina, Chapel Hill; Kristin Smith, PhD, University of New Hampshire; and Shila Soneji provided helpful feedback and suggestions. These individuals received no compensation for their contributions.

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