I am a physician taking care of a woman with bad asthma who requires admission

Read another response by Jyl Gentzler
Read another response about Ethics, Medicine
I am a physician taking care of a woman with bad asthma who requires admission to the hospital. She happens to be six months pregnant, which is clinically relevant because low oxygen levels in the blood will affect the fetus. I inform her that if she refuses treatment, her unborn child will suffer oxygen deprivation, and will likely be mentally retarded. She says that "God will take care of us, I'm going home."