Some do. A recent pregnancy, abortion, ovarian cysts, polycystic ovary syndrome (PCOS), untreated hypothyroidism, and early signs of menopause can all decrease the reliability of the test at detecting the LH surge and fertile days. So can fertility drugs containing LH itself, or others containing human chorionic gonadotrophin. You should check with your doctor about when it is appropriate to begin testing if you are taking medication to treat infertility in women who don't ovulate.