Hi How many weeks pregnant are you? Injection Ovunal contains Human Chorionic Gonadotrophin ( HCG). In pregnancy normally this hormone is secreted by placenta. It promotes secretion of progesterone from the corpus luteum of ovary. Progesterone is necessary for maintaining the pregnancy. There is some evidence that injection HCG MAY help in implantation. That is why your doctor must have prescribed it. But there is no clear proof. If I were your doctor I would have prescribed progesterone vaginal pessary 400 mcg vaginally daily untill completion of three months of pregnancy. Its efficacy and safety in the treatment of threatened abortion is proven. I hope I have answered to your satisfaction.