An ovulation predictor kit OPK) is a test that checks your urine for ovulation. More specifically, it checks for the presence of LH, luteinizing hormone, which rises shortly before ovulation.
Normally, LH is in a steady state and at a low level (negative test). When it rises very quickly (LH surge), LH stimulates the developing egg (follicle) and ovulation (release of the egg) follows shortly thereafter. The OPK can often help predict when you are about to ovulate.
Ovulation usually happens within 12-36 hours after the OPK first turns positive, right after the LH surge is first detected. The problem with using the OPK exclusively to determine exactly when you should make love is that ovulation could have already happened when the OPK first turns positive and making love after ovulation will not get you pregnant.
This is especially true if you test only once every 24 hours. To predict ovulation and to determine the best time to have sex for getting pregnant, you may want to test twice a day, once in the morning, the other time in the early after noon.
To optimize your chances getting pregnant, you should not wait to have sex only when the OPK turns positive. You should make love regularly 2-3 times a week every week, plus once a day every day during your fertility phase (the time prior to and the day of ovulation). That way you can make sure you will not miss the all important fertile days.
LH is increased shortly before ovulation although when a woman enters menopause and her ovaries stop working, LH levels will still also rise. LH can also be increased in some situations associated with primary ovarian failure:
- Developmental defects: Ovarian agenesis (failure to develop ovaries), chromosomal abnormality, such as Turner's syndrome, ovarian steroidogenesis defect such as 17 alpha hydroxylase deficiency
- Premature ovarian failure: which can be due to radiation, chemotherapy, or autoimmune disease
- Chronic anovulation: the failure to ovulate can be due to polycystic ovary syndrome (PCOS), adrenal disease, thyroid disease, or ovarian tumor