The menstrual cycle is a dynamic process. It is repeated on a monthly basis and is characterized by specific symptoms, which may change and intensify with age. Recording the first day of the menstrual cycle and understanding the process are two important steps to taking charge of your health and your life.
Menstruation
The menstrual cycle starts on the first day of menstruation and is the beginning of the menstrual phase. This is often referred to as the last menstrual period, or LMP, by healthcare providers. It is worth marking this day on a calendar for medical reasons or if pregnancy is a possibility.
Proliferative Phase
The proliferative phase is characterized by the growth of a follicle on one of the ovaries. The follicle can be seen on ultrasound as a clear, black spot called a cyst. It contains the ovum. As the follicle grows, it secretes increasing amounts of estrogen, called estradiol. The estradiol causes the endometrium, the inner lining of the uterus, to thicken. Sonographically, the endometrium has the appearance of three lines.
Ovulation
With the help of luteinizing hormone, the ovum within the dominant follicle reaches maturity. The wall of the follicle weakens, breaks, and releases the ovum. This is the fertile period during the menstrual cycle. Women are most fertile anywhere from five days before ovulation until one or two days after. Some women experience pain during ovulation, called mittelschmerz, and may experience spotting. It is not uncommon for women to have a clear, vaginal discharge during this stage of the menstrual cycle.
Luteal Phase
The secretory, or luteal phase, is influenced by the corpus luteum on the ovary. The corpus luteum is the dominant follicle after it releases the ovum. Estradiol drops significantly compared to the proliferative stage and levels off. The corpus luteum releases progesterone, the hormone responsible for preparing the endometrium for blastocyst implantation should pregnancy occur. It is also necessary for maintaining the pregnancy through the first trimester until the placenta matures. Sonographically, the corpus luteum starts as a cystic structure and evolves to a mixture of cystic and solid components and, finally, to a solid structure that heals much like a bruise.
Progesterone causes many of the symptoms known as premenstrual syndrome. This can include bloating, constipation, acne breakouts, breast tenderness and mood fluctuations. At the end of the luteal phase, the corpus luteum essentially clears up and the estradiol and progesterone levels drop. This triggers menstruation, the first day of the menstrual cycle.
Ultrasound performed during ovulation and the secretory stage may produce false positive results – a report that there is an abnormality even though the structures seen are part of a perfectly normal process. It is recommended that pelvic ultrasounds be performed during the end of menstruation or the beginning of the proliferative stage to minimize false positives.
The average menstrual cycle is 28 days, although many women experience variable cycle lengths. Some women may have a 23-day cycle followed by a 28-day or even a 32-day cycle. Women should take the time to observe and learn about their menstrual cycle. Recognizing what is normal for oneself may help identify any future problems, if they arise. Women who know where they are in their cycle may also be able to identify why they may feel depressed and sluggish one week, and confident and strong the next.
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