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Pregnancy

The Menstrual Cycle and Ovulation

The time of ovulation is one of the most important things a woman should understand about her body since it is the determining factor in getting pregnant and preventing pregnancy. The process can be confusing and somewhat overwhelming when trying to understand. If you still have further questions regarding ovulation, it may be helpful to talk with your health care provider. Being informed on what your body does, can help you feel more in charge of your health.

What Happens During the Menstrual Cycle?

So, what is actually happening inside your body each month? It’s all about hormones. The changes associated with the menstrual cycle are brought on by fluctuations in hormones at different times of the month. Most cycles are 29 days long - a variation of a few days more or less can be quite normal and small variations from cycle to cycle is also normal. Day 1 of bleeding is referred to as Day 1 of the menstrual cycle. The length of the cycle is measured from Day 1 of one cycle (bleed) to Day 1 of the next cycle (bleed)

Ovulation occurs on approximately day 14 of a woman’s cycle and is when a mature egg is released from the ovary, pushed down the fallopian tube and is available to be fertilized. The lining of the uterus has thickened to prepare for a fertilized egg. If no conception occurs, the uterine lining as well as blood will be shed. The shedding of an unfertilized egg and the uterine wall is the time of menstruation. The menstrual cycle can be divided into the following parts: the ovarian cycle and the uterine cycle.

Ovarian Cycle

The ovarian cycle involves changes in the ovaries, and can be further divided into two phases:

Phase 1

The follicular phase (days 1 through 13) is the time from the first day of menstruation until ovulation, when a mature egg is released from the ovary. It's called the follicular phase because growth or maturation of the egg is taking place inside the follicle, a small sac where the egg matures. Ovulation occurs around day 14 of the cycle, in response to a surge of luteinizing hormone (LH) when the egg is released from the ovary. This first half of the cycle can differ greatly for each woman lasting anywhere from 7 days until 40 days.

Phase 2

The luteal phase (days 14 through 28) is the time from when the egg is released (ovulation) until the first day of menstruation, when you get your period. It is a structure that grows in the ovary where a mature egg was released at ovulation. The luteal phase has a more precise timeline and usually is only 12-16 days from the day of ovulation. This ultimately means that the day of ovulation will determine how long your cycle is.

Stress and Your Period

The old thought that stress can affect your period is only partly true. Stress can affect your ovulation which ultimately determines when your period will come, but stress around the time of an expected period will not make it late—it was already determined when it would come 12-16 days earlier!

Important Facts to Know About Ovulation:

Uterine Cycle

The uterine cycle involves changes in the uterus. It occurs in tandem with the ovarian cycle, and is divided into two phases:

The proliferative phase (days 5 through 14) is the time after menstruation and before the next ovulation, when the lining of the uterus increases rapidly in thickness and the uterine glands multiply and grow.

The secretory phase (days 14 through 28) is the time after ovulation. When an egg is not fertilized, the corpus luteum gradually disappears, estrogen and progesterone (hormone) levels drop, and the thickened uterine lining is shed. This is your menses (your period).

When are you the most fertile?

A woman's monthly cycle is measured from the first day of her menstrual period until the first day of her next period. On average, a woman's cycle normally is between 28-32 days, but some women may have much shorter cycles or much longer ones. Ovulation can be calculated by starting with the day the last menstrual period (LMP) starts or by calculating 12-16 days from the next expected period. Most women ovulate anywhere between Day 11 - Day 21 of their cycle, counting from the first day of the LMP. This is what many refer to as the "fertile time" of a woman's cycle, because sexual intercourse during this time increases the chance of pregnancy. Ovulation can occur at various times during a cycle, and may occur on a different day each month.

How can tracking your ovulation be useful?

Tracking ovulation can help a woman get a better idea of when pregnancy can and can not occur during her monthly cycle Fertility Awareness is one way to track when ovulation occurs and it includes studying the changes in cervical mucus and using a basal thermometer. Cervical fluid will change to a wet, slippery substance that resembles "egg whites" just before ovulation occurs and until ovulation is over. A thermometer helps track a body temperature rise, which signals that ovulation has just occurred. Another way to track ovulation is through ovulation kits and fertility monitors.. Once ovulation has occurred, there is nothing you can do to increase your chances of pregnancy. Your next step is to begin watching for early pregnancy symptoms.

Before getting pregnant - What you should know

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This article is a NetWellness exclusive.

Last Reviewed: Dec 08, 2008

Arthur T Ollendorff, MD Arthur T Ollendorff, MD
Associate Professor of Obstetrics and Gynecology
College of Medicine
University of Cincinnati