Release of the ovum or egg is called ovulation. Once the egg is released from the ovary and matures in the fallopian tubes, it will survive and be able to be fertilized for a very short time, at most about 24 hours and as a little as 8 hours. The other half of the conception process is the spermatozoa (sperm). Healthy sperm can fertilize an egg for about 48 hours or more after their deposit in the woman. Sperm usually requires at least 24 hours to reach the egg.

It takes a woman's body several days to prepare for ovulation. This process is managed by complex interaction of hormones. About a week before ovulation, a threshold of increasing amounts of the hormone estrogen is reached. At this time, one ovum is selected from among the many available in either of the two ovaries. This one ovum begins to grow and the uterus begins to be prepared to receive a possibly fertilized egg.

At the same time, other hormones are changing the amounts of minerals like sodium and potassium (electrolytes) that are kept or discarded by the body. This is what produces the Cue Peak, a high point in the Cue salivary readings of electrolytes.
 

A few days after the Cue Peak, the luteinizing hormone (LH) in the blood increases and decreases very sharply over a period of 24 hours (the LH peak). LH is the hormone that triggers the release of the ovum from the ovary. The egg is released within 24 hours after the LH is at its highest in the blood.

Some time (as much as 12 hours) after the peak of LH in the blood, LH is also present in the urine. It is this increasing concentration of urine LH that can be detected by the different brands of urine-based ovulation predictors. Prediction using this method depends on the exact relationships between the time of the highest blood LH, the time the urine stick begins to see the LH, and the time of the measurement. At best, the time between the urine signal and actual ovulation cannot be more than 18 hours in advance. At worst, it is seen only after ovulation has already occurred, offering no chance of conception for the current cycle.

Use of the Cue Vaginal sensor allows the user to confirm when ovulation has occurred. As LH reaches its peak in the blood, there is a definite change in the reproductive tract. Mucus secretion increases, and the electrolyte content of the mucus changes. This change causes a sharp, clear drop and increase in these readings. It is this nadir that the Cue uses to confirm ovulation. <BACK>