Hi, Thanks for the query. Gestin contains allylestrenol. It is a progesterone. Progesterone usually helps in maintainance of pregnancy and in preventing miscarriage. There are different types of progesterones. Allylestrenol belongs to category C drugs in pregnancy according to FDA. Means animal studies have shown some adverse effects on fetus but sufficient human studies are lacking. So, this can be used when the benefits overweight the risks. Better to use natural micronized progesterones as per as possible. Miscarriage before few years may not have effect on present pregnancy. But better to be careful and continue with regular antenatal checkups and ultrasound examinations. Take care.