Association of the 2021 Child Tax Credit Advance Payments With Low Birth Weight in the US.

Importance: Infants and pregnant people in the US fare worse on almost all health measures compared with those in peer nations. Families in the US are more likely to live in poverty and have a less generous social safety net, which has generated debate over the contribution of economic conditions to this disparity.

Objective: To assess the association between temporary increases in income during pregnancy through the 2021 expanded Child Tax Credit (CTC) and birth outcomes.

Design, Setting, And Participants: This cross-sectional study applied a comparison-population, interrupted time series design to data from US birth certificates (January 1, 2014, through December 31, 2021) to test whether the log odds of low birth weight (LBW) among monthly cohorts of births exposed to the CTC would coincide with a decreased incidence of LBW. All singleton live births to US residents aged 15 to 49 years with available data were included.

Exposure: Monthly birth cohorts exposed to the CTC were defined as those born to parous people during the CTC advance payment period from July through December 2021.

Main Outcomes And Measures: The main outcome was the natural logarithm of the odds of LBW (<2500 g) among monthly birth cohorts.

Results: Among included births (n = 28 866 466), 61.2% were to parous people, the majority were to people aged 20 to 39 years (91.7%), and 6.5% were born LBW. The odds of LBW increased above expected values in 5 of the 6 months of the CTC payments (range of increases, 3.3%-5.4% across the 5 months). The outlier-adjusted odds of LBW increased, on average, by 4.2% (95% CI, 2.7%-5.7%) among the monthly birth cohorts exposed to the CTC.

Conclusions And Relevance: This study found that the odds of LBW among birth cohorts exposed to the CTC increased above expected values in 5 of the 6 months of the CTC advance payments. Additional research is needed to evaluate rival explanations for this increase in LBW among births exposed to the CTC payments.