Saturday, July 23, 2011

Calendar Method Vs. OPK? It's All In The Timing...


So my husband and I are trying for our first child. We've trying for about 3 months with no luck yet. i was thinking of trying the ovulation test but i'm not sure if its worth it. I've read online that they can help but i figure it would never hurt to ask. Do you know much about them and if there worth the money or should i just track my temp every morning.Thanks for the help! S. from Canada


Hello S. from Canada,

An ovulation predictor kit (OPK) does not help any more than timing it well. I don't recommend it to my patients. Instead, I recommend the calendar timing method. It goes like this:

CD#1 The day your period starts. Mark you calendar then count each day. For instance the next day is cycle day #2, then cycle day #3 etc.

CD#10 Stop having intercourse. You can have regular intercourse until that day but you have to stop on that day.

CD#13-17 Assuming you have normal regular cycles, this is your fertile period. You should have intercourse each day, only once per day and only one ejaculation per episode. After cycle day #17 you can resume your normal frequency.

Keep in mind that 85% of women under the age of 30 take 8-12 months to achieve pregnancy so you have not yet been trying long enough. Hopefully this method will help.

Good Luck,
Dr. Edward J. Ramirez, M.D., FACOG
Executive Medical Director
The Fertility and Gynecology Center
Monterey Bay IVF Program
Monterey, California, U.S.A.

Comment: Ok thank you so much for the advice! I'm going to try the calendar method.


  1. It surprised me that you suggested ignoring ovulation predictor kits, given how variable women's cycles are. Even with a "normal" (actually, many studies have shown that fewer than 15% of women have a 28 day cycle) cycle, the follicular phase can vary dramatically, depending on if there's a luteal phase defect.

    It would seem prudent to use OPKs for a cycle or two to figure out what "timing it well" means for S. from Canada. A generic recommendation that CD 13-17 is her fertile period is just a guess.

  2. Hello,

    The definitive study of menstrual cycles was a large study of 30,000 cycles involving more than 2300 women and showed that the mean cycle length was 29.1 days with a standard deviation (margin of error) of 7.5 days. The average length was 28.1 days. So although there are patients with variability, the majority of women with regular menstrual cycles will be pretty close to 28 day cycles, but as you've pointed out, not necessarily 28 days.

    The calendar method certainly does not work for women that have irregular menstrual cycles, which is women with cycles of 21 days or less or 35 days or more. In these patients the OPK would not be of benefit because this is an indication of an underlying ovulation or ovarian problem. It could be a luteal phase defect, as you've mentioned, or some other hormonal dysfunction, but the bottom line is that all the steps necessary to achieve a pregnancy will be interrupted.

    Therefore, the calendar method assumes that the cycle is regular and predictable. Otherwise, it will not work. I am assuming that S. from Canada has a regular cycle. Certainly that was a fact that I did not put in my answer that should have been made clear. In actuality, the best way to use the calendar method, as I instruct my patients, is to follow and note the dates/lengths of three natural cycles to determine the average length. If it is regular then the luteal phase is automatically determined to be 14 days and ovulation would occur the day prior. So I have them take the average length, and count back 14 days. The fertile period is then set to occur four five days starting from two days prior to the presumed ovulation day, include the presumed ovulation date and two days after the ovulation date. There is no method, including OPK's that can predict ovulation exactly.

    As you probably know, OPK's are not without cost and can cost upwards of $60 per month the last time I checked. I don't know if prices have decreased. OPK's basically detect the LH surge which then narrows the timeline for ovulation to 24-48 hrs. Still the exact timing of the ovulation is unknown and the exact start of that timing is unknown. If a woman checks in the morning and the surge begins in the evening that will affect the timing, as an example. Because of this inherent unpredictability, one has to fudge to time their intercourse, which is the same thing the calendar method does. You blanket the presumed ovulatory period to make sure there is fresh sperm there when the egg gets picked up. The calendar method is a way to help save $60 per month. If a person has regular cycles, I don't think it is worth that cost when the calendar method can work just as well.

    Thanks for your comment and allowing me to clarify my response.

  3. Appreciate your thorough response!

    One of the reasons I'm sensitive to this is that I have a close-to-normal (and "regular" by your definition) 31-32 day cycle, but my luteal phase is only 12 days. So my ovulation typically happens around day 18-19.

    And yes, the luteal phase problem would likely make it difficult to stay pregnant, but discovering that is important. As a 4+ year infertility patient, I know how frustrating it is to try something and only after it's failed "long enough" find out there's something else that's the root cause.

    Ovuquick is $50 for a 9 day test supply, but that's the creme de la creme of OPKs per my ob/gyn. Clearblue's digital kits run $38 for 20 tests.

    Temping is another way to get some insight into a cycle, and only costs what a basal thermometer costs, but I personally found it too tedious and was willing to spend the $20/month for OPKs for a few months. The combination is what revealed my luteal phase defect, so I was able to go to my doctor and provide that information.

    Thanks for the good dialogue!

  4. Hello Brave IVF Girl,

    Thanks for your comments and discussion. OPK's, as well as BBT, are certainly options for patients to consider and decide individually. With the cost that you cite at $20 per month, that is reasonable in patients whose cycles are a little off, but again, if the cycles are fairly regular, it is not absolutely necessary.

    The luteal phase defect in your case, would need to have been treated and timing was not the only problem. The normal recommendation is for a patient to try on their own for 6-12 months and if then they are unsuccessful, to seek counsel with an infertility specialist. The infertility specialist would have been able to detect the LPD by end of cycle endometrial biopsy and treat it appropriately with supplemental progesterone or tried to correct the ovarian function with super-ovulation.

    However, if the only problem you had was timing and the OPK helped with that, then indeed it is a testimony showing the benefit of OPK. I, on behalf of my readers, who like to know if the OPK was helpful to you i.e. were you successful using this method?



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