Hi, Thanks for posting in HCM. Susten is a tablet containing progesterone and is generally considered safe in pregnancy. Doctors prescribes it in doses of 200-300 mg twice a day and is given to prevent abortion and sustain pregnancy. It can be taken vaginally, orally or rectally....though the best mode seems to be vaginally. The cardiac activity of the baby would appear around 6 weeks, but most often picked up by ultrasound scan by 8 weeks. Kindly take the medication as prescribed and get a scan done during 8th week to know about the status and progress of pregnancy. Hope the information provided would be helpful. All the best.