What is a normal menstrual cycle? How many days should there be in between periods? Which days are the most/least fertile?

E.

The length of your cycle is the interval in days between the first day of flow of one period and the first day of flow of the next period. The normal menstrual cycle ranges from 25 to 35 days, with a 28-day average.

The menstrual flow itself (abbreviated AF on many internet chat groups) can last two to seven days, with an average of four days. We arbitrarily consider the first day of menstrual bleeding as Day 1 of your cycle. Spotting before the menstrual flow should not be considered the start of your period.

The period of time before ovulation is labelled the follicular phase; during this time, the ovary prepares to release one or more eggs. The duration of this phase can vary. The half of the cycle after ovulation is called the luteal phase and coincides with the ovary's production of progesterone. This portion of the cycle lasts 11-14 days.

For conception, sperm need to be in place before ovulation. Ideally, you should have intercourse one to three days beforehand.

Many women monitor their menstrual cycles with basal body temperature (BBT) charts to find out when they ovulate. This involves taking your temperature when you awake each morning, before you get out of bed, while your temperature is at its lowest for the day. When you ovulate, your basal body temperature typically rises about half a degree Fahrenheit. However, this method is not very accurate; studies have shown that you can ovulate up to three days before or after the temperature rise. Some women worry if their BBT chart shows a luteal phase is less than 14 days. Don't worry. First, it is impossible to accurately pinpoint ovulation using the BBT; second, studies have not demonstrated that a short luteal phase is a fertility problem.

If you are using a BBT, by the time you see the temperature rise, you have probably already ovulated and it is too late to have intercourse that month for conception purposes. The value of a BBT chart is to help you find patterns in your cycle, so you can predict ovulation for future months. Once you can predict the day of your cycle on which the rise is likely to occur, start with intercourse about four days before the expected rise and repeat every other day for about a week.

The best way to pinpoint ovulation, though, is by using a urine LH kit to test your urine each day around the middle of your cycle. A color change on the test stick predicts that ovulation will occur within the next 18-36 hours. For more details on this, see my website. If you are using a test kit, begin intercourse on the day the stick changes color.

For a more detailed discussion of this topic, see my earlier column Calculating the Fertile Period.