Period or menstruation normally happens once every month for most women. However, it is not uncommon for a period to come irregularly.

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The irregular menstrual cycle can be an early sign of serious conditions, but it does not mean that you have serious illnesses whenever you have a late period.

To understand why period can come late, it might be better to understand the menstrual cycle.

Understanding The Menstrual Cycle

menstrual cycle

There are 3 stages that your body goes through during the period. These stages are:

Follicular Stage

The stage starts on the first day of the cycle until the ovulation stage. During this stage, the pituitary gland stimulates a hormone called follicle-stimulating hormone (FSH). These hormones then stimulate the ovaries to produce multiple egg-filled sacs called follicles.

Among the many follicles, one follicle will grow bigger than the rest and this dominant follicle will produce estrogen hormone.

The estrogen hormone thickens the uterus lining and provides nutrients to enhance the growth of embryos.

Ovulation Stage

The estrogen stimulates the pituitary gland to produce another hormones called luteinizing hormones (LH). The spike in LH hormones causes ovulation.

This is the period of menstrual cycle that is most fertile and it is the best time to get pregnant.

Ovulation happens when the ovary releases a mature egg which then travels to the fallopian tube.

Luteal Phase

During the luteal phase, the dominant follicle will turn into a corpus luteum (mass cells) that releases both estrogen and progesterone.

During this phase, if the egg is fertilized, the corpus luteum will support early pregnancy. But, if no fertilization occurs, the corpus luteum will be reabsorbed by the body and this causes a decrease in estrogen and progesterone levels.

During this stage, your body will experience what is known as a pre-menstruation syndrome (PMS). And then the cycle will restart every month.

Reasons That May Cause Your Irregular Periods

Having irregular menstruation does not necessarily mean that something is wrong with the cycle. Here are several reasons that may cause an irregular period.

1. Stress

Stress has been the most common reason for irregular or late period. Stress affects the hypothalamus to regulate the period.

Additionally, stress also affects the length of the menstrual cycle. Research found numerous correlations between high-stress levels and longer menstrual cycles.

2. Weight loss and obesity

Weight loss and obesity have also been known to cause irregular periods. Normally, women who are 10% below the normal percentage on the BMI scale experience irregular or missed periods.

Similarly, obesity can also affect women’s menstrual cycles the way weight loss does. It is recommended to consult to your ob-gyn regarding obesity and irregular period as there may be a slight chance of it being related to Polycystic Ovary Syndrome (PCOS).

3. Birth control

When you start getting birth control, there may be major changes to the regulation of your hormones. However, birth control pills especially ones that contain progestin and estrogen can also help stimulate periods.

4. Polycystic Ovary Syndrome (PCOS)

Aside from stress, PCOS is also one of the most common conditions that cause irregular periods. Women who have PCOS tend to have abnormal hormones. These imbalance hormone levels can cause cysts to form.

The cysts cause irregular periods or periods that disappear altogether. Cysts can be diagnosed with ultrasound with your ob-gyn.

5. Thyroid Diseases

The thyroid is a gland that produces thyroid hormones. When you have thyroid diseases, it can cause an imbalance in the production of the hormone. Too little or too many thyroid hormones affect the flow of menstruation.

When To See A Doctor?

If you are experiencing an irregular or late period, it might be better to consult your preferred ob-gyn and have it resolved as soon as possible.

Go to or download our mobile app, and choose your preferred method of meeting your Gynecologist.