Fertility Window Chart

Why is the fertile window chart in the manual different from the one on the OV-Watch website?

The fertility window data shown in the manual for OV-Watch and the fertility window data shown on the OV-Watch website may show different data points but essentially are supporting the same premise. That premise debunks the myth that many women have, that you are only fertile on the day of ovulation and the day after.  In 1994, Dr. Robert Hatcher published the chart below (Hatcher et al, Contraceptive Technology, 16th revised edition, Irvington Publishers, 1994, pp. 537-539). This data was published in our printed materials because at the time it was the best data we found in the literature explaining the probability of conception during the 6 day “fertile window” as described by Dr. Alan Wilcox in his seminal article in the New England Journal of Medicine in December, 1995. While as you can see the chart allows for a chance of conception after ovulation this was in contradiction to what Dr. Hatcher says on page 537 of his book “that intercourse prior to ovulation is key to maximizing the chance of pregnancy” and that that the ovum may only have a life span of 12 hours or less.

See chart below Fig. 1:

However, after the brochures were printed we discovered even more compelling literature that was presented to the American College of Obstetrics and Gynecology by Dr. Dunson and published in Statistics in Medicine that used his modeling methods with the data of other researchers most notably the data from Wilcox’s study. It is based on a higher number of women and a higher number of cycles.

You can see in the fertility window chart below (fig. 2)

Dunson found that conception is possible from intercourse beginning 5 days before ovulation extending only through the day of ovulation, not the day after. In fact it was noted that no pregnancies occurred the day after ovulation. So, the highest probability of conception occurs with intercourse on the days prior to ovulation, rather than the day of ovulation itself. Since spermatozoa may survive for 5-7 days in the female reproductive tract, by taking advantage of your 4 days before ovulation and the day of ovulation- you are maximizing your chances of conceiving.

We began marketing OV-Watch discussing the advantages of the 6 day fertile window but we now know that OV-Watch’s biggest advantage is not that it provides the 6 days (which by definition of the fertile window it does) but that it provides the most crucial 4 days before ovulation- the time when a woman is most likely to conceive.

LH or estrogen detecting products (urine sticks or the urine monitor) by definition cannot provide the 4 days before ovulation. Since these hormones are not detectable that early in a woman’s cycle. Knowing 4 days before instead of hours before ovulation, allows a woman time to decide when to have sex, and the opportunity for multiple times of intercourse, causing less stress and greater opportunity for pregnancy to occur.

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