I don't know if that particular area does but they can in Texas and there have been a number of cases where the baby was taken from the mother based on such drug tests.
There are real reasons for the tests. Children whose mothers have used while carrying the baby have specific health issues that need to be addressed as early as possible and many people consider taking drugs while pregnant to be blatant child abuse.
if you're on a government-assisted healthcare program and/or doctor is aware of prior drug use or any other history of mother's life which could incriminate, i.e. jail time served, testing is mandatory, I believe