They are not legally preventing you from getting pre-natal care--they are refusing to allow you to be absent from work for this reason; you still can get the pre-natal care, but may not be able to work at this employer while doing so. That is, unfortunately, most likely legal: the law does not actually require employers to allow employees to take any time off for illness or medical care--unless, that is, the Family and Medical Leave Act or a like state law is involved, which I do not believe is the case here. (For example: FMLA allows qualified employees from covered employers to take time off for child birth or to take care of a newborn--but not for prenatal care.)It is voluntary on the part of employers whether they provide sick days or make any accomodations for sickness or medical care, such as allowing even unpaid time for a doctor's visit. Since it is voluntary to do these things, employers are essentially free to set whatever policy they like--including not permitting an employee to go to a doctor's appointment during work hours, unless he or she has and is using a sick day for that purpose.