I need to reprimand an employee & decrease her her hours to Part-Time as needed, who has been spoken with twice & written up three times. However, she is five months pregnant - I'm unsure of this issue due to the Pregnancy Discrimination

I need to reprimand an employee & decrease her her hours to Part-Time as needed, who has been spoken with twice & written up three times. However, she is five months pregnant - I'm unsure of this issue due to the Pregnancy Discrimination Act. I need assistance in writing a reprimand outline, staying within the legal boundaries. Thank you, Robin