Guttmacher Institute:

Abortion has become more concentrated among poor women

…
The growing concentration of abortion among women with incomes below the federal poverty line likely reflects a combination of factors. Between 2000 and 2008, the proportion of women in the overall population who were poor increased by 25%. And a Guttmacher study published in the Fall of 2009 showed that the deep economic recession may also have played a role, as financial concerns led more women to want to delay childbearing or limit the number of children they have.

So the sonogram law would have disproportionately affected poor women.
What a surprise.