Estimating the effect of timing of earned income tax credit refunds on perinatal outcomes: a quasi-experimental study of California births

Background: The largest poverty alleviation program in the US is the earned income tax credit (EITC), providing $60 billion to over 25 million families annually. While research has shown positive impacts of EITC receipt in pregnancy, there is little evidence on whether the timing of receipt may lead to differences in pregnancy outcomes. We used a quasi-experimental difference-in-differences design, taking advantage of EITC tax disbursement each spring to examine whether trimester of receipt was associated with perinatal outcomes. Methods: We conducted a difference-in-differences analysis of California linked birth certificate and hospital discharge records. The sample was drawn from the linked CA birth certificate and discharge records from 2007–2012 (N = 2,740,707). To predict eligibility, we created a probabilistic algorithm in the Panel Study of Income Dynamics and applied it to the CA data. Primary outcome measures included preterm birth, small-for-gestational age (SGA), gestational diabetes, and gestational hypertension/preeclampsia. Results: Eligibility for EITC receipt during the third trimester was associated with a lower risk of preterm birth compared with preconception. Eligibility for receipt in the preconception period resulted in improved gestational hypertension and SGA. Conclusion: This analysis offers a novel method to impute EITC eligibility using a probabilistic algorithm in a data set with richer sociodemographic information relative to the clinical and administrative data sets from which outcomes are drawn. These results could be used to determine the optimal intervention time point for future income supplementation policies. Future work should examine frequent income supplementation such as the minimum wage or basic income programs.