How To Restore Menstrual Cycle When Pregnant?

Dear Doctor, My girlfriend claims she is 6-7 weeks pregnant and that the doctors have told her she has fetal derangement. She has been prescribed 30mg of Progestogen/Duphaston daily. We live in Vietnam-she is Vietnamese, I am English. I have scoured the internet and the only information I can glean is that Duphaston is used to restore a normal menstrual cycle. She is 30 years old. I'm 35.