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We utilize our patients’ observations about their bodies, physical examination, ultrasound, hormone testing and evaluation of tissue samples (biopsies) to evaluate the menstrual cycle. We monitor the menstrual cycle in order to determine whether and when normal ovulation is occurring. We also will monitor the menstrual cycle in order to determine the dosage and timing of fertility drugs.
What Every Fertility Patient Should Know About the Menstrual Cycle
During the first half of the ovulation cycle, a small cystic structure called a follicle grows within one of a woman’s ovaries. The ovarian tissue around the follicle produces the hormone estrogen. Estrogen circulates to the cervix, stimulating the production of mucus. Mucus provides a pathway through which sperm may ascend to the uterus and fallopian tube. Estrogen circulates to the lining of the uterus (endometrium) where it causes that tissue to grow. Estrogen probably is necessary for creating a proper environment in the fallopian tube for fertilization to take place.
At mid cycle, the pituitary gland releases a surge of the hormone luteinizing hormone (LH). The LH surge causes the ovarian follicle to rupture, releasing the egg from the ovary. The LH surge also cause the egg within the follicle to undergo maturational changes which allow that egg to be fertilized. Finally, the LH surge initiates the secretion of progesterone from the follicle. The follicle, now called the corpus luteum, secretes progesterone from ovulation until menstruation.
Progesterone circulates to the uterus where it causes changes that allow the endometrium to receive the egg for implantation. Progesterone counteracts the stimulation effects of estrogen on cervical mucus.
If pregnancy occurs, the newly implanted egg will release a hormone known as human chorionic gonadotropin (hCG). HCG circulates from the uterus to the ovary where it maintains the production of estrogen and progesterone for several weeks until the pregnancy itself takes over the production of these hormones. In the absence of pregnancy, progesterone levels will drop two weeks after ovulation. The drop in progesterone level precipitates menstrual bleeding.
How Do You Know if You’re Ovulating?
Women are often able to identify some of these ovulation cycle-related changes within their own bodies. A woman may be aware of clear, slippery, stretchy mucus secretion from the vagina occurring in the days before ovulation. Mucus secretion will normally peak on the day prior to ovulation although many women sense this peak several days before ovulation.
Some women are aware of the growth and rupture of their follicle. Midcycle pain, often localized to one or the other side of the pelvis, is called mittelschmerz. Mittelschmerz most often occurs on the day of ovulation. However, awareness of pain in the pelvis can sometimes occur on days before or after ovulation.
Once ovulation has occurred, some women become sensitive to the presence of progesterone. If a woman records her daily temperature, she may note a rise of at least 0.4 F which will occur once progesterone secretion has commenced. After several days of secretion, progesterone may cause bloating and breast tenderness. It is likely that changes in estrogen and progesterone during the second half of the cycle are responsible for the physical and psychological changes we call premenstrual tension.
What Can a Doctor or Nurse Tell About Your Ovulation?
Utilizing physical examination, we may detect changes associated with the menstrual cycle. A physician or nurse may visualize the cervix and obtain a sample of mucus for microscopic evaluation. Changes in cervical secretions reflect changes in the hormones which are produced throughout the menstrual cycle by the ovary. We also look for sperm swimming in the cervical mucus. Occasionally, during a physical examination the physician will detect enlargement of one of the ovaries, which reflects the development of a preovulatory follicle.
What is the Role of Ultrasound?
Ultrasound is an important device which we use to monitor the ovulation cycle. With ultrasound we can visualize preovulatory follicle(s). In an unstimulated menstrual cycle (i.e., no fertility drugs) a woman will usually raise up (recruit) a single follicle. This follicle is seen as a small cystic structure within one of the ovaries on ultrasound. That follicle will normally grow to 18-24 mm. size prior to rupture. Ultrasound can predict the approximate time of ovulation and determine whether or not the follicle has truly ruptured and released the egg for fertilization.
Ultrasound evaluation of follicles is even more important when fertility drugs are administered, since it allows the physician to determine the number and ripeness of follicles so that ovulation can be further stimulated and triggered in a safe fashion.
Using ultrasound the physician can also determine the thickness of the endometrial lining. We recognize that the lining of the uterus must achieve a certain minimum thickness in order for there to be a good expectation that implantation will take place.
What is the Role of At-Home Urine Testing?
Hormone determinations are often used to monitor the menstrual cycle. The most often evaluated hormone is urinary luteinizing hormone (LH). The LH surge can be identified by patients with the use of ovulation monitoring kits. We recommend that LH kits be run at least once a day, beginning at least one day prior to the earliest expected day of the LH surge. We advise that patients test the second urine of the day (regardless of the instructions contained in the kits that they have purchased). Women should empty their bladder as soon as they awake in the morning. As soon as they can produce a second specimen (and before they drink much fluid) they should produce a second specimen for testing. In certain critical and special situations, we will ask our patients to run their LH kits twice each day.
The LH surge occurs approximately 36 hours prior to the release of the egg. It takes a few hours for the hormone (which is released into the blood stream) to be excreted in a patient’s urine. Moreover, since the test is only run once per day, ovulation may occur either sooner or later than 36 hours after the LH surge is identified. In general, we expect ovulation to occur some time on the day following the detection of the LH surge.
What is the Role of Blood Testing?
In addition to LH measured in urine, a number of hormones can be measured in blood. These include estrogen (estradiol), progesterone, LH, and follicle stimulating hormone (FSH). Estrogen levels reflect the health and vigor of a patient’s follicle(s). In an unstimulated cycle, estradiol levels will normally exceed 150 pg/ml prior to ovulation. A low peak estradiol level may indicate weakness of ovulation. When there are multiple follicles (as with fertility drugs), interpretation of estrogen levels is more complicated. Levels reflect the combined secretions of estrogen by a number of follicles which may be at different stages of development.
Progesterone is normally secreted after ovulation. However, small amounts of progesterone may “leak” out of the ovary just before ovulation. If too much progesterone is secreted before ovulation, we believe that the conditions in the cervix and the lining of the uterus may be somewhat “spoiled.” We utilize subtle changes in progesterone levels to best time the triggering of ovulation.
As we have discussed, LH triggers the process of ovulation. We can utilize LH levels in blood to identify the onset of ovulation for the purpose of timing inseminations and other procedures. Also, we can detect when a patient on an injectible fertility drug initiates ovulation on her own, prior to our triggering ovulation with a shot of hCG.
In a few situations the physician will elect to obtain an endometrial biopsy, a tissue sample from the lining of the uterus, in order to monitor events of ovulation. This sample is normally taken a week or more after ovulation. The sample reflects the stimulation of the lining of the uterus by estrogen and progesterone. It predicts the ability of the endometrium to allow a fertilized egg to implant. Endometrial biopsies are occasionally useful in evaluating the ovulation process in women who have experienced multiple miscarriages.
We offer this explanation of ovulation and ovulation monitoring to our patients so that they can “think along with us” as we strive to evaluate ovulation and achieve pregnancy. All of us in the office welcome your questions and observations so that we can do a better job.