Understanding Your Menstrual Cycle

The menstrual cycle refers to the cyclical development and then shedding of the endometrium, the lining of the uterus. Understanding your menstrual cycle is important if you want to chart your fertility patterns, predict ovulation, and increase your chances of becoming pregnant.

A woman's fertile period during her menstrual cycle, on average, lasts about seven days: seven days before ovulation (the release of the egg), the day of ovulation, and the day after ovulation. After this, chances of conception decrease quickly, as the egg has a short life-span of about 24 hours.

Given this somewhat narrow window of opportunity for conception, understanding the menstrual cycle can help increase a woman's chances of becoming pregnant. The key is to predict ovulation with as much precision as possible. Of course, both the length and regularity of menstrual cycles vary greatly among women - so successful ovulation prediction depends both on understanding the general dynamics of the menstrual cycle, as well as a woman's own unique cycles and patterns.

The Menstrual Cycle and Ovulation Prediction

The menstrual cycle is divided into two parts: pre-ovulation and post-ovulation. The ovarian cycle refers to the cyclical development and expelling of the egg from the ovary. Though the length and regularity of a menstrual cycle may differ, the average duration of a complete menstrual cycle is 28 days (though healthy cycles can run from 21-36 days). Below you will find an overview of a typical menstrual cycle with an image map based on a 28 day cycle length.

Pre-Ovulation

"Day 1" of the menstrual cycle is the day bleeding begins. Bleeding - or "menstrual flow" - last about three to five days. By the seventh day of the cycle, eggs in the ovaries begin to ripen due to various hormonal changes. Between the seventh and the eleventh days, the lining of the uterus begins to thicken and it is possible to observe changes in the presence and consistency of cervical fluids. After the eleventh day, luteinizing hormone cause the egg that is most ripe to be released from the ovary and begin its travel down the fallopian tubes to the uterus. For women with a 28-day cycle, ovulation (the release of the egg) should take place on about the 14th Day - or the very middle - of the menstrual cycle.

Post-Ovulation

The period after ovulation is called the luteal phase, and it is marked by a slight, but clearly measurable, increase in body temperature. Following ovulation, the egg travels the fallopian tube toward the uterus. If the egg is fertilized by a sperm (conception), then " implantation" should take place in the uterus (if implantation takes place outside the womb, this is an ectopic pregnancy. Ectopic pregnancy can occur in several places - but the most common is in the fallopian tube). Pregnancy begins if "implantation" occurs. If the egg is not fertilized, it will "expire" in about 24 hours. Without fertilization, levels of certain hormones will decrease , causing the lining of the uterus to break down and shed - otherwise known as menstruation, or a woman's "period". The first day of bleeding is "Day 1" of the next menstrual cycle.

The first part of the cycle, from menstruation to ovulation, may vary from 14 to 20 days in length. The length of the pre-ovulation phase is often different from one woman to another - but it can also differ from month to month for an individual. It is during first part of the cycle that fertilization can occur. Of course, regular menstrual patterns can be altered by illness, insomnia, stress, physical exertion, and physical and emotional changes.

The luteal phase, or post-ovulation (from ovulation to menstruation), is generally the same length for most women - averaging about 14 days. As a rule, the egg is released 10 to 16 days before menstruation, or the start of the next menstrual cycle. If you have heard the term DPO on preconception chats, this refers to "days past ovulation". High sensitivity pregnancy tests can allow you to begin testing for pregnancy at around 7-10 days past ovulation.

Part II >
The Dynamics of Conception and Fertility:
What Happens During Ovulation?

Related Topics
> The Luteal Phase
> Ovulation FAQ
> Definition of Cycle Terms