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Fertility Aids

Ovulation Predictor Kits (OPKs)

The LH Surge, Ovulation & Pregnancy

A pregnancy begins with conception. A child is conceived when the male sperm successfully fertilizes the female egg. Successful fertilization is most likely during a 24 hour period one to three days following the LH surge. Since this ovulation "window" only opens once per month, and for only about 24 hours, being able to predict fertility it is very helpful when trying to become pregnant. Therefore, you should have intercourse during the one to three day period following the LH surge to increase chances of conception.

Luteinizing hormone (or LH) in elevated quantities causes ovulation (the release of the egg - or ovum - from the ovarian follicle). During the menstrual cycle only a small amount of LH is made, but in the middle of the cycle LH briefly and dramatically increases. This increase is called the "LH surge" and precedes ovulation. Conception is most likely to occur within thirty-six hours following the LH surge. The LH Ovulation Test is specifically designed to detect your LH surge - the time when you are likely to ovulate. If you receive a positive on an lh test, you are in your most fertile phase of your menstrual cycle.


Ovulation Predictor KitsDetermine the length of the menstrual cycle. The length of the menstrual cycle is the number of days from the first day of menstrual bleeding to the day before bleeding begins on the next period.

Ovulation Predictor KitsDetermine the usual length of the menstrual cycle over the last few months. Next subtract 16 from this number and this will give you the day you should begin testing. (i.e. Average cycle length of 29 days: 29-16=13 You would begin testing on Cycle Day 13) If your cycle is less than twenty-one days or greater than forty days, consult a physician.

Test once per day, at about the same time between 10:00 A.M. and 8:00 P.M. Do not use first morning urine as a sample.

Many women will test once per day until they approach the usual day of ovulation and begin testing 2 or 3 times a day several hours apart. This ensures that they "catch" the surge, as some women have a very short LH surge.

Interpretation of Results

To determine your result, compare the color intensity, (i.e. shade of color, lightness or darkness of color) of the test band to the control band. In determining a positive or negative result, it is important to compare the color intensity, for this will indicate whether or not the LH surge (indicating ovulation) is in progress.

Positive for the LH Surge
If the test band is of equal or greater intensity (equal or darker) than the control band, this is a positive result and a good indication that the LH surge is occurring.

Negative for the LH Surge
If the test band is of lesser intensity (lighter) than the control band or cannot be seen, this means the LH level of the sample is at or near its basal (normal) level and that the LH surge is not in progress.

How to Recognize the LH Surge

After each test, you must decide if you are having an LH surge. If your test result is positive, you are probably having an LH surge. An LH surge can last from one to three days. Ovulation is most likely to occur sometime in the day and a half following the first day of the LH surge.

If your test result is negative, you are probably not having an LH surge. Remember that a pink-rose test band lighter than the control band shows that there is only a very low level of LH in your urine.

When To Stop Testing

Unless otherwise specified by a doctor, stop testing once the LH surge is detected. Six to ten days of testing may be needed to detect the LH surge, though additional testing may be required.

Ovulation Predictor Kits Ovulation Predictor Kits (Dip Strips)

Ovulation Predictor Kits (Midstream)