What is a Menstrual Cycle Chart?

A menstrual cycle chart is a tool for tracking the menstrual cycle. A typical chart will have space to record such items as basal body temperature, occurrence of intercourse, quality of cervical fluid, and the texture and position of the cervix. Some charts also may include statistics such as vaginal sensation, ovulation and pregnancy test results, and other factors that influence the menstrual cycle, such as alcohol consumption, amount of sleep, and stress or illness. When this data is recorded every day, it can create a picture from which a woman can gauge when she is fertile and when she will get her period. These charts also may help a woman know whether her periods are normal and regular.

Experts consider basal body temperature, or body temperature immediately upon waking from at least three hours of sound sleep, to be one of the most telling data points on a menstrual cycle chart. At the start of a woman's menstrual cycle, when she gets her period, her temperature is generally low. When she ovulates, her temperature will likely spike due to the increase in progesterone in her system and will remain high until she once again begins to menstruate. By charting her basal body temperature over the course of several months, a woman can learn on what day of her cycle she has historically ovulated and use that information to predict when she will ovulate again. If her temperature remains high for more than 18 days after ovulation, she may also be able to ascertain that she's pregnant.

While other data is simply noted in columns on a typical menstrual cycle chart, basal body temperature is commonly graphed. Each day's temperature point is connected to the next, helping to clearly illustrate the two phases of the menstrual cycle. By counting the last six days before ovulation and marking the temperature one tenth of a degree above the highest temperature during that time, a woman can discern where to draw her cover line — a straight line that covers the entire month of data. Though a woman's temperature may fluctuate within each phase, a normal graph will usually show a set of low temperatures beneath the cover line, followed by a set of higher temperatures above it, which indicate that she has ovulated.

The quality of a woman's cervical fluid is another data point experts consider essential to understanding the menstrual cycle. Before ovulation, cervical fluid may be creamy and white or thin and clear. As ovulation nears, most women produce a slippery, clear, gel-like fluid, commonly referred to as "egg white mucus," that is an ideal medium for sperm. At the peak of fertility, experts say this fluid should be stretchy enough to spread it into a string several centimeters long between forefinger and thumb. After ovulation, cervical fluid may get sticky and quickly dry up, as it is no longer needed to conduct sperm to the egg. Combined with the information gleaned from charting her temperature, a woman can use the quality of her cervical mucus to judge precisely where she is in her menstrual cycle.

Whether or not a woman is trying to get pregnant, keeping a menstrual cycle chart can shed light on her body's natural rhythms. Knowing when she is fertile, when she is unlikely to become pregnant, and when she will get her period can help her plan ahead. Sharing her chart with her doctor can also help her identify issues that may affect her health or ability to conceive.