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Irregular Periods

To know what an irregular period is, first a regular menstrual cycle needs to be defined.  The length of the menstrual cycle is calculated from the first day of a period until the first day of the next period.   On average, a woman should expect to have a period every 28 days, but anything from 21-35 days is considered normal.  The days during which menstrual bleeding occurs is also part of the cycle, and that ranges from 2-7 days.   There can be light bleeding, heavy bleeding, or a combination of both during this time. Bleeding that does not fall within this pattern is considered abnormal or irregular.

Examples of abnormal or irregular periods include:  Bleeding between periods (intermenstrual bleeding or metrorrhagia), longer-lasting very heavy periods (menorrhagia), cycles shorter than 21 days (polymenorrhea), and cycles longer than 35 days (oligomenorrhea).

What can cause irregular bleeding?

Maturation of the hypothalamic-pituitary-ovarian hormonal axis

When a girl starts to menstruate, it may take up to two years for her cycles to regulate—-a process known as the maturation of the hypothalamic-pituitary-ovarian hormonal axis.  During this time frame, periods can range anywhere from every two weeks to just once or twice per year and can be heavy or light.  This irregularity stems from the lack of regular ovulation (the release of an egg from the ovary).

Perimenopausal hormonal fluctuations

Perimenopause is the transitional time before menopause.  During perimenopause, the ovaries produce fewer hormones (estrogen and progesterone), causing ovulation to become irregular, and, in turn, causing the menstrual cycle to become erratic.  Irregular periods are generally the first sign of perimenopause.  Bleeding can be heavier or lighter than usual.  This pattern of irregular bleeding can last for several years leading up to menopause—when periods cease (by definition, for 12 consecutive months) because there are there are no more eggs for ovulation and ovarian hormone production ceases.

Pregnancy/Breast feeding

Pregnancy and breast feeding can lead to amenorrhea, or the absence of periods, for longer than a year, but this should not be considered menopause.

Polycystic Ovarian Syndrome (PCOS)

PCOS is a very common hormonal imbalance problem for women of childbearing age.  Women with PCOS may have many cysts on their ovaries, and they may not ovulate because they have high levels of androgens (male-like hormones) which affect the hormonal dynamics of the menstrual cycle.  This results in missed or irregular periods.

Thyroid hormone imbalance

Abnormal thyroid hormone levels—which result when the thyroid gland doesn’t produce enough thyroid hormone (hypothyroidism, or underactive thyroid) or it produces too much thyroid hormone (hyperthyroidism)—can cause irregularities in the menstrual cycle.  Other metabolic disorders such as obesity and diabetes can also cause irregular cycles.


Stress, whether emotional or physical, causes the production of cortisol, which can wreak havoc on the hypothalamus-pituitary-ovarian hormonal axis mentioned earlier, and result in irregular periods.


The use of hormonal contraception, such as oral contraceptives (the “pill”), the vaginal ring (NuvaRingR), the patch, DepoProveraR injection, and hormonal implants (like the MirenaR IUD and NexplanonR) can lead to much lighter periods because they make the lining of the uterus thinner.  They can also cause intermenstrual bleeding during the first months of use until the body adjusts to the hormones.

Uterine fibroids

Uterine fibroids, which are benign tumors of the uterine muscle that typically develop during the reproductive years, vary in size and position and in the degree to which they may affect menstrual bleeding.  If they affect menstrual bleeding, it is to make it heavier and irregular (typically intermenstrual bleeding).  While the exact reason fibroids cause heavy periods is unknown, they are known to distort the lining of the uterus and affect the way the uterus contracts.

Endometrial polyps

Endometrial polyps are benign growths that arise from the lining of the uterus (the endometrium) and extend into the uterine cavity.  They are usually benign and most often occur in women who are going through or have completed menopause.

They may be asymptomatic, but sometimes cause frequent, unpredictable episodes of bleeding of variable duration and heaviness or intermenstrual bleeding.

Pelvic infection

A pelvic infection that involves the uterus, and possibly the tubes and ovaries, known as Pelvic Inflammatory Disease (PID) can cause irregular periods because of inflammation and irritation of the endometrium.

We at Adaptive Gynecology understand how concerning irregular periods can be. With our extensive experience we will work to diagnose and address the cause.

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