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Normally, one of the ovaries releases a single mature egg every month, and this is called ovulation. Women may notice pain or abdominal discomfort at the time of ovulation and occasionally have some slight vaginal bleeding. The presence of regular periods, premenstrual tension and dysmenorrhoea (period pains) usually indicate that the menstrual cycles are ovulatory.
Eggs are stored in the ovaries in follicles. Follicles exist in two major categories - growing and non-growing ( primordial ). Eggs in the primordial follicle are in a very immature form. In this state they are not capable of being fertilized by a sperm until they undergo a maturing process which culminates in their release from the ovary at the time of ovulation.
Egg maturation and ovulation is stimulated by two hormones secreted by the pituitary - follicle stimulating hormone (FSH) and luteinizing hormone (LH) . These two hormones must be produced in appropriate amounts throughout the monthly cycle for normal ovulation to occur.
Every month, at the start of the menstrual cycle, in response to the FSH produced by the pituitary gland, about 30-40 primordial follicles start to grow. Of these, only one matures to form a large fluid-filled structure, called a Graafian follicle which contains a mature egg, while the others die ( a process called atresia). The mature egg is released from the follicle when the follicle ruptures in response to a surge of LH produced by the pituitary.
After ovulation has occurred, the follicle from which the egg has been released forms a cystic structure called the corpus luteum. This is responsible for progesterone production in the second half of the cycle.
You can see an excellent animation ( which will open in a new browser window) of the hormonal changes which occur during a normal menstrual cycle at Serono Fertility Lifecycle.
Most women who have regular periods have ovulatory cycles. Women who fail to ovulate or who have abnormal ovulation usually have a disturbance of their menstrual pattern. This may take the form of complete lack of periods (amenorrhoea), irregular or delayed periods (oligomenorrhoea) or occasionally a shortened cycle due to a defect in the second part (luteal phase) of the cycle.
Fig 1. Schematic of the ovarian follicle during its development (clockwise)
Fig 2. The hormonal changes which occur during a normal ovulatory cycle, if pregnancy occurs. The purple line marks the point when the embryo implants.
Detecting ovulation - when do you ovulate?
Menstrual period timing ( Calendar method)
To determine the length of the menstrual cycle, one only needs to note the date of the beginning of the menstrual period (first day of flow) for two consecutive periods, and then count the day from one date to the next. Keeping track of the length of menstrual cycles will help determine the approximate time of ovulation, because the next period begins approximately two weeks from the date of ovulation.
The rough rule to calculate the approximate date of ovulation is : NMP minus 14 days, where NMP is the ( expected) date of the next menstrual period. This is because the luteal phase for most women is 14 days long.
Keeping track of the menstrual cycle by charting it can indicate other ovulatory disturbances . For example, if a menstrual cycle that is normally 28 days starts to occur every 35 or 40 days, this may mean that ovulation is disturbed, and an evaluation is needed.
Basal Body Temperature (BBT) chart
During the luteal phase of the cycle, the corpus luteum produces the hormone progestrone, which elevates the basal body temperature. When the basal body temperature has gone up for several days, one can assume that ovulation has occurred. However, it is important to remember that the BBT chart cannot predict ovulation - it cannot tell you when it is going to occur !
The basal temperature chart can be a useful tool. It allows the patient to determine for herself if she is ovulating as well as the approximate date of ovulation, but only in retrospect. Basal body temperature charts are easy to obtain and the only equipment required is a special BBT thermometer.
General instructions for keeping a basal body temperature chart include the following :
- The chart starts on the first day of menstrual flow. Enter the date here.
- Each morning immediately after awakening, and before getting out of bed or doing anything else, the thermometer is placed under the tongue for at least two minutes. This must be done every morning, except during the period.
- Accurately record the temperature reading on the graph by placing a dot in the proper location. Indicate days of intercourse with a cross.
- Note any obvious reason for temperature variation such as colds, or fever on the graph above the reading for that day.
The major limitation of the BBT is that it does not tell you in advance when you are going to ovulate - therefore its utility in timing sex during the fertile period is small. Interpreting the BBT chart can be tricky for many patients - rarely do the charts look like those you see in textbooks!
Also, keeping a BBT chart can be very stressful - taking your temperature as the first thing you do when you get up in the morning is not much fun. What is worse is that you start to let the BBT chart dictate your sex life. This is why though the BBT chart used to be a useful method in the past, it's utility is limited today - and newer methods are available which are more accurate are available. We advise our patients never to chart their BBTs - we feel they are just a waste of time.
Manufacturers have now incorporated a microprocessor along with the digital thermometer, to create an electronic fertility management device , called The Bioself Fertility Indicator. This makes calculation of the "fertile days" much easier, because it combines and optimises both the basal body temperature and calendar method of ovulation prediction.
Fertility Software Programs
Newer software programs ( easily available on the internet), such as CycleWatch, help you learn about your body's fertility signs by giving you the tools to document and analyze your observations. For women who are comfortable with computers, this is a useful tool to organize your cycle data and analyze your cycles to determine fertile times.
You can also use our free online fertility calculator to determine when you ovulate !
After ovulation, the endometrium is prepared for implantation of the fertilized egg by the progesterone secreted by the corpus luteum. In order to determine if ovulation is occurring normally, an endometrial biopsy used to be done in the past . During this procedure, a small amount of endometrium from inside the uterine cavity is extracted surgically and sent for pathologic examination under a microscope. This is a standard procedure usually done just before the period begins. It can be done in the doctor's office or in an operating theater. No anesthesia or hospitalisation is needed. However, it does cause discomfort during the procedure (about as much as a severe menstrual cramp) and an analgesic can be taken a half-hour prior to the procedure to decrease this discomfort.
When examining the endometrial biopsy, the pathologist looks for the influence of the estrogen and progesterone hormones on the endometrial glands. If progesterone has been produced in that cycle, the endometrial glands show secretory changes . In fact, the effect of progesterone on the endometrium is so predictable, that the biopsy can be "dated" - that is, the pathologist can predict on which day the next period will start! If there is a "lag" between the predicted day and the actual day, then this suggest a luteal phase defect, which means that the production of progesterone is deficient. If no progesterone at all has been produced, then the endometrium will be reported as being proliferative (under the influence of only estrogen) - which suggests that the cycles are anovulatory (i.e., ovulation did not occur in that cycle).
Because an endometrial biopsy is painful and provides limited information, few doctors use it anymore.
A curetting used to the commonest procedure done for infertile patients. In fact, a number of infertile patients will request that a curetting be done for them, since they feel that the curetting will "clean out" the dirt they have in their uterus and allow them to conceive. This is an old wive's tale and is based on " I know someone who got a baby after a curetting".
The correct technical term for curetting is D and C - dilatation and curettage - which means the cervix is stretched (dilated) and the uterine cavity scraped (curetted) to collect the endometrium) . This is an obsolete procedure for an infertile woman, and can actually be harmful. The only use of a D&C is to provide endometrial tissue which can be examined under the microscope to see if the woman is ovulating or not. It has absolutely no fertility-enhancing role whatsoever.
Since this endometrium can be obtained much more easily, safely and cheaply with an endometrial biopsy (in which only a strip of endometrium is removed) there should rarely be any need to do a D&C for an infertile woman. Patients have often have repeated D&Cs - and these can actually damage the cervix and even block the tubes, if infection occurs after surgery. The only possible role for a D&C today is when tuberculosis of the uterus is suspected.
Blood test for progesterone
The progesterone level in the blood may be measured to confirm that ovulation has taken place. This test is done on Day 21 of the cycle (about 1 week after the expected date of ovulation) . A normal level is between 10 ng/ml - 20 ng/ml and indicates that the corpus luteum is producing enough progesterone, and is good retrospective evidence that ovulation occurred. A very low level means that the cycle was most probably anovulatory. An intermediate level may suggest a luteal phase defect (in which the corpus luteum does not secrete enough progesterone).
While the above tests will tell a women whether or not she ovulates, the following symptoms and tests which can be used in order to determine when you ovulate are of greater importance, since they provide information which can be used to identify the "fertile period" prospectively.
Cervical mucus (Billing's method)
By checking your cervical mucus daily, as described in the chapter on the cervical factor, you can determine when you ovulate. Just before ovulation, your cervical mucus is thin, profuse, clear and stretchy, like raw egg whites. After ovulation, the mucus becomes thick, tacky, scanty and sticky. You can learn to appreciate this change in your mucus (by seeing and feeling it) and this allows you to predict when ovulation occurs quite accurately. You can learn the technique for tracking your cervical mucus in the Chapter on The Cervical Factor.
Approximately 25 percent of women may experience a pain on one side of the abdomen that is associated with ovulation. This is called mittelschmerz (a German word, which means midcycle pain) and is usually related to the release of an egg from the rupturing follicle. It is a good idea to mark the date when it occurs since this information is helpful in determining when ovulation occurs.
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