Hello dear Understand your concern Duphaston contain progesterone. It make the uterine more favorable for pregnancy. It maintain healthy pregnancy in low progesterone case and prevent miscarriage. As you had spotting after intercourse, it may be due to low progesterone, injury to vagina, pre cancerous condition of cervix and vagina and vaginal infection. So above cause should be rule out along with low progesterone. Go for blood progesterone level. If found low should to take duphaston. It does not cause any adverse effect on pregnancy and fetus. It should be taken under advice of gynecologist and periodic follow up will be required. Avoid sexual intercourse during pregnancy. Hope this may help you Best regards Dr. Sagar Dholariya