Hello, No untoward effect on the fetus. Absolutely safe. In women, progesterone is responsible for the development of a healthy womb lining (endometrium) that is necessary for pregnancy. The body produces progesterone at certain times of the menstrual cycle, causing the womb lining to flourish. If a fertilized egg does not attach to the womb lining by the end of the monthly menstrual cycle, the levels of progesterone in the body decrease. This causes the body to shed the womb lining (a menstrual ‘period’). If a fertilized egg successfully attaches to the womb lining by the end of the monthly cycle, progesterone levels in the body remain high. This helps maintain a healthy womb lining for the ongoing pregnancy. As dydrogesterone helps regulate the healthy growth and normal shedding of the womb lining, it may be used in the treatment of menstrual disorders such as absent, irregular or painful menstrual periods, infertility, premenstrual syndrome and endometriosis. It may also be used to minimise the overgrowth of the womb lining due to oestrogen (the main female sex hormone) in hormone replacement therapy (HRT) following menopause. By maintaining the womb lining, dydrogesterone is also useful in helping prevent miscarriage (spontaneous abortion) in women who have suffered repeated miscarriages or who may miscarry. Hope I have answered your query. Let me know if I can assist you further. Take care Regards, Dr AJEET SINGH, General & Family Physician