Lady Comp


Do you have any references or reviews about the product “Lady Comp” as an NFP method? Is it reliable?


Lady Comp is a brand name of one of the many gadgets available to use to monitor fertility. The reliability and usefulness of these gadgets—which measure anything from temperature, to ferning patterns in saliva, to ovarian hormones—vary widely.

The Lady Comp is little more than a thermometer. When a woman ovulates, her temperature rises with her rising progesterone levels. The Lady Comp, or Baby Comp, is a fancy (expensive) thermometer produced in Germany which records these daily temperature readings. It stores the readings, and “charts” them for the couple. The computer then displays a light that indicates fertile (red), infertile (green) or what they call a transition or learning phase (yellow) which are days that “might” be fertile. One can accomplish as much with a thermometer at much less cost.

My concern about the lady comp is the claim it can identify the beginning of fertility as well. I contacted one site which offers the device, and asked how the device could identify the beginning of fertility. The response I received was that “This computer works on the basal body temperature method. This way it is possible to detect the slight rise in temperature at the beginning of the ovulation period.” As anyone familiar with basal body temperature knows, temperature cannot identify the beginning of fertility, only the end of it! The rise follows ovulation, NOT the beginning of the fertile days.

The sites I reviewed in preparing an answer to your question all made the same claim, that the device accurately identifies the beginning and end of fertile days (the red light days). The sites I reviewed did not offer any explanation of how the monitor does this, just that the longer you use it the better it knows your body and the less “yellow” or uncertain days you will have.

I can only conclude the lady comp identifies the beginning of fertility by storing cycles of temperature rises, and based on this history projects when the temp will rise in the current cycle. Can you say rhythm? Because a “computerized device” is used, many assume this to be an advancement in Natural Family Planning, when in fact it is calculating the beginning of fertility based on a history of cycles, not prospectively. This is a step backwards, not an advancement.

If women want to take their temperature, they would be just as well using a reliable but inexpensive basal body thermometer and a chart to graph their temperatures. If they like gadgets, and do not want to graph their own temps, they may enjoy using the lady comp for this purpose. However, this device should not be relied on to identify the beginning of the fertile phase. That is identified by they onset of cervical mucus, which this device does not monitor.

In healthcare, as in other things, we sometimes can fall into the trap of a high tech solution that does not offer any more information than the low tech one, and in fact may actually be less informative. In my review of the lady comp, I do think this is a perfect example of that. This monitor is a poor substitute for seeing an expert in Natural Family Planning and learning to understand fertility and be familiar with our own bodies. Yes, it may appeal to some who want a shortcut, and as a gadget which takes your temp is probably just fine. But for an effective family planning method, I recommend contacting one of the Professionals at to learn a much more modern and reliable approach, which will not only identify the beginning and end of fertility, but be suitable for navigating the variations which occur in breastfeeding, pre-menopause, post pill, infertility, etc.

Answered By:

Sheila St. John
Sheila St. John is the Executive Director of the California Association of Natural Family Planning, coordinating the non-profit’s education and advocacy efforts throughout the state. Initially attracted to NFP as a healthy, effective method for planning families, drug, device and surgery free, her passion for NFP has grown over the last 42 years as she has journeyed with the over 900 couples she has personally instructed in its use, and been privileged to witness its role in overcoming infertility, women’s health, and the transformation that occurs in lives of men, women, and families, when we embrace God’s design for love and life.

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