Income gains and very low-weight birth among low-income black mothers in California.

We test the hypothesis suggested in the literature that an acute income gain in the form of the earned income tax credit reduces the odds of a very low-weight birth among low-income non-Hispanic black mothers. We apply ecological time series and supplemental individual-level logistic regression methods to monthly birth data from California between 1989 and 1997. Contrary to our hypothesis, the odds of very low-weight birth increases above its expected value two months after mothers typically receive the credit. We discuss our findings in relation to the epidemiologic literature concerned with ambient events during pregnancy and recommend further investigation.