Estimating Women’s Eligibility for 

WIC: Postpartum and Breastfeeding 

Women

Linden McBride, Maria Perez Patron, and Renuka Bhaskar 

U.S. Census Bureau

FCSM Research and Policy Conference

October 25, 2022

Any opinions and conclusions expressed herein are those of the authors 

and do not reflect the views of the U.S. Census Bureau. This analysis 

uses only publicly available data.
Special Supplemental Nutrition Program for 

Women, Infants, and Children (WIC)

2

Source:https://www.census.gov/library/visualizations

/interactive/wic-eligibility-participation.html

● WIC serves 11 million women, infants, and children 

nationally (Gray et al., 2022)

● 85% of eligible postpartum and 52% of eligible pregnant 

women participate (Gray et al., 2022)

● Current Census research product estimates infants and 

children eligible for and accessing WIC 

○ Linked administrative and survey data

○ Substate estimates by county, demographics

 Identify the underserved

○ Eligible women not estimated
Eligibility

Developing estimates of WIC-eligible women presents some challenges

● Categorical eligibility

○ Pregnant 

○ Postpartum (up to 6 months after end of pregnancy)

○ Breastfeeding (up to infant’s first birthday)

● Data availability

Objective: Identify postpartum women in the ACS and develop a predictive model to estimate the 

number of those who are breastfeeding infants between 6-12 months of age

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Eligibility

Developing estimates of WIC-eligible women presents some challenges

● Categorical eligibility

○ Pregnant 

○ Postpartum (up to 6 months after end of pregnancy)

○ Breastfeeding (up to infant’s first birthday)

● Data availability

Objective: Identify postpartum women in the ACS and develop a predictive model to estimate the 

number of those who are breastfeeding infants between 6-12 months of age

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Correlates of Breastfeeding

+ Older maternal age, being married, higher education level, and access to 

private insurance (Jones et al, 2015)

+ NH-White and Hispanic (Li et al., 2019)

+ Foreign-born (Singh et al., 2007)

+ Non-English speaking household (Parasuraman et al., 2020)

- NH-Black (Li et al., 2019)

- Poverty (McKinney et al., 2016)

- Acculturation among foreign born (Singh et al., 2007)

- Single mother, and lower household education (Parasuraman et al., 2020)

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Model Development: National Survey of 

Children’s Health (NSCH) 2017-2019

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• Household survey, U.S. Department of Health and Human Services 

• Produces national estimates on the physical and emotional health of children

• Questions to identify breastfed infants and breastfeeding duration: 

• Was this child EVER breastfed or fed breast milk?

• How old was this child when they COMPLETELY STOPPED breastfeeding (or are they STILL 

breastfeeding)?
Model Application: American Community Survey 

(ACS) 2019 1-Year Public Use Microdata Sample 

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• Household survey, U.S. Census Bureau

• Produces estimates on the socio-demographic, economic, and housing characteristics of 

the US population

• Allows us to identify income-eligible and their demographic characteristics; currently 

used to estimate characteristics of WIC-eligible infants and children 

• Questions to identify postpartum women and presence of their infants

• In the PAST 12 MONTHS, has this person given birth to any children? 

• What is Persons n’s age?
Analytic Sample

NSCH 2017 - 2019

Restrict to children ages 0 to 4 years living in households with mothers present: 

• 17,000 obs, representing 17.2 million children; 44.67% were breastfed 6 months or longer 

Split into training and testing sample, drawing randomly from within strata (Wieczorek et al., 2022) 

• 2⁄3 training 

• 1⁄3 hold out sample 

ACS 2019

Restrict to infants living in households with mothers present:

• 26,000 observations representing 3.1 million infants and 2.8 million postpartum women

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Features for Model Development (NSCH 

2017-2019)

Time of survey

Mom’s employment status, mom’s education, mom’s marital status, state of residence, total 

number of children in the household, number of individuals in the household, household language, 

mom’s military status, child’s health insurance status, ratio of household income to federal poverty 

line, whether household is accessing SNAP

Time of birth

Mom’s age, mom’s duration in the U.S., sex of infant, race and ethnicity, nativity of mom (and 

household), number of older siblings

Target Being breastfed 6 months or longer

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Features for Model Development (NSCH 

2017-2019)

Time of survey

Mom’s employment status, mom’s education, mom’s marital status, state of residence, total 

number of children in the household, number of individuals in the household, household language, 

mom’s military status, child’s health insurance status, ratio of household income to federal poverty 

line, whether household is accessing SNAP

Time of birth

Mom’s age, mom’s duration in the U.S., sex of infant, race and ethnicity, nativity of mom (and 

household), number of older siblings

Target Being breastfed 6 months or longer

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Model Development

Models

● Logit (LR)

● Random Forest (RF)

● Extreme Gradient Boosting (XGB)

Two approaches in model training 

● “Full” : age 4 and younger 

○ Training, testing samples ~7600 obs, ~3800 obs

● Restricted: age 6-12 months

○ Training, testing samples ~560 obs, ~280 obs

Both approaches are validated (3-fold cross validation) on subsample of 6-12 month olds

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Model Development

Models

● Logit (LR)

● Random Forest (RF)

● Extreme Gradient Boosting (XGB)

Two approaches in model training 

● “Full” : age 4 and younger 

○ Training, testing samples ~7600 obs, ~3800 obs

● Restricted: age 6-12 months

○ Training, testing samples ~560 obs, ~280 obs

Both approaches are validated (3-fold cross validation) on subsample of 6-12 month olds

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Training Fold 

Training Fold 

LR

RF

XGB

Testing Fold

Training

Hold out sample

NSCH 2017 -2019
Results

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Source: Authors’ estimates, NSCH 2017-2019
Results

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Source: Authors’ estimates, NSCH 2017-2019
Results

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Source: Authors’ estimates, NSCH 2017-2019
Results

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Source: Authors’ estimates, NSCH 2017-2019
Results

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Source: Authors’ estimates, NSCH 2017-2019
XGB Feature Importance 

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Applied to ACS 2019 1-Year, Infants with 

Mothers Present

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Fold 

Fold 

Fold 

LR

RF

XGB

ACS 2019

Source: CDC 2022 Breastfeeding Report Card, 

Authors’ estimates, NSCH 2017-2019, ACS 2019 

1-Year PUMS
Applied to ACS 2019 1-Year, Infants with 

Mothers Present

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Fold 

Fold 

Fold 

LR

RF

XGB

ACS 2019

Source: CDC 2022 Breastfeeding Report Card, 

Authors’ estimates, NSCH 2017-2019, ACS 2019 

1-Year PUMS
Limitations

● We can’t separate biological and adoptive mothers in the NSCH

● NSCH provides estimates of being breastfed, not the breastfeeding 

practices of mothers

● Known undercount of infants and young children in survey data 

(census.gov, 2021) → will lead to undercount of postpartum and 

breastfeeding women

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Conclusion

● Promising start on identifying postpartum and breastfeeding 

women; room for improvement

Next steps

● Finalize models (hyperparameter tuning)

● Move to restricted use ACS and NSCH

● Compare predictive model with NSCH-ACS linked estimates

● Apply income-eligibility criteria to identify WIC-eligible postpartum 

and breastfeeding populations

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References

Jones, J. R., Kogan, M. D., Singh, G. K., Dee, D. L., & Grummer-Strawn, L. M. (2011). Factors associated with exclusive breastfeeding in the United States. Pediatrics, 128(6), 1117-1125.

Jones, K. M., Power, M. L., Queenan, J. T., & Schulkin, J. (2015). Racial and ethnic disparities in 

breastfeeding. Breastfeeding Medicine, 10(4), 186-196.

Li, R., Perrine, C. G., Anstey, E. H., Chen, J., MacGowan, C. A., & Elam-Evans, L. D. (2019). Breastfeeding trends by race/ethnicity among US children born from 2009 to 2015. JAMA pediatrics, 173(12), 

e193319-e193319.

McKinney, C. O., Hahn-Holbrook, J., Chase-Lansdale, P. L., Ramey, S. L., Krohn, J., Reed-Vance, M., ... & 

Shalowitz, M. U. (2016). Racial and ethnic differences in breastfeeding. Pediatrics, 138(2).

Singh, G. K., Kogan, M. D., & Dee, D. L. (2007). Nativity/immigrant status, race/ethnicity, and 

socioeconomic determinants of breastfeeding initiation and duration in the United States, 2003. 

Pediatrics, 119(Supplement_1), S38-S46.

US Census Bureau. (2018). 2016 National Survey of Children’s Health: methodology report. 

https://www.census.gov/content/dam/Census/programs-surveys/nsch/tech- documentation/methodology/2016-NSCH-Methodology-Report.pdf
CDC Estimates (National Immunization Survey 2019)

Source: CDC 2022 Breastfeeding Report Card
ROC/AUC