A young black women could have a child before the age of 19, because of systemic racism from the lack of generational wealth much more available to white women. Or maybe the traditional redlining of neighborhoods with better schools led her to grow up somewhere with worse schools.
As far as systemic racism is concerned it doesn't matter whether the discrimination occurred in the past or today - if it is still affecting that race then its racism. Are you really claiming that the centuries of oppression that legally continued right into the 1960s are just coincidental to black suffering?
And yes some of today's racist practices - like our tax structure and refusal to redistribute wealth are starting to affect some poor white people as well. That doesn't somehow let these practices off the hook for targeting.
For instance American incarcerates people at a rate higher than all but 2 or 3 countries. Some of the incarcerated people are white but incarceration happens at a higher rate for black people. That's systemic racism even if the drug law being invoked doesn't directly mention race.
The point of the midwifery programs being effective is that it points to a problem beyond just "stress" IE systemic racism induced suffering or age of birth or marital status. These black woman are not getting health care that would save their children.
Whether or not some poor white women are also not getting adequate health care doesn't make what is happening to these black woman less racist. The "targeting" of the systemic racism doesn't have to be 100% accurate to count as racism.