Hello, Letroze (letrozole) is commonly prescribed as an infertility treatment especially in women with polycystic ovary syndrome (PCOS) to conceive. Let me explain its mode of action so that you can get an insight about its possible side effects which are well tolerated. Letrozole works by inhibiting aromatase thereby suppressing estrogen production. Aromatase is an enzyme that is responsible for the production of estrogen in the body so when this enzyme is inhibited by the letrozole, estrogen levels are suppressed. This results in the brain and pituitary gland increasing the output of FSH (follicle-stimulating hormone) which helps in ovulation (release of egg from the ovary). As far as the side effects are concerned, generally, it is well tolerated by most women however low estrogen levels can cause hot flashes, headaches, and breast tenderness. There is no documented evidence of any harmful effects on the growing baby. So, in view of the above you can take it safely as prescribed by your doctor for the treatment of infertility associated with PCOD. Hope I have answered your query. Let me know if I can assist you further. Take care Regards, Dr Mohammed Taher Ali, General & Family Physician