The first menstrual bleeding in adolescent girls usually occurs between the ages of 12 and 13. Before its onset, you may often notice the appearance of a whitish discharge. This is not a sign of illness and should not be a cause for concern – it indicates that the ovaries are functioning properly and that the first menstruation (menarche) is likely to occur soon. Shortly before the first period – and often before subsequent ones – you may experience mild pain in the lower abdomen or lower back.

The first menstrual periods can vary in intensity, ranging from light spotting to heavier bleeding, and usually lasts between 3 and 5 days. To avoid being caught off guard, it is a good idea to carry a sanitary pad with you once the first signs appear.

Remember that menstruation is the culmination of the process of sexual maturation. It occurs only after your body has undergone the physical changes from a young girl into a young woman.

Menstrual bleeding results from the shedding of the uterine lining (endometrium), which is expelled through the vagina. Menstruation prepares the uterus for the next cycle, during which the lining rebuilds and transforms to create favorable conditions for the possible implantation of a fertilized egg. During menstruation – especially in the first two days – strong uterine contractions help detach the endometrial lining. These contractions may cause pain in the lower abdomen or back. Such discomfort can often be relieved by magnesium supplements or antispasmodic medications. If the pain is particularly severe, it is important to consult a doctor to rule out conditions such as endometriosis, uterine fibroids, anatomical abnormalities of the reproductive organs, or inflammation.

Common accompanying symptoms include headaches or migraines, nausea, swelling (edema), irritability, and anxiety. These symptoms are often referred to as PMS (premenstrual syndrome). Natural and effective remedies that may help alleviate PMS symptoms include magnesium and evening primrose oil. A light diet with reduced salt, sodium, and fat intake, along with regular physical activity, can also be beneficial.

The menstrual cycle begins on the first day of menstrual bleeding and ends on the day before the next bleeding starts. The number of days of menstruation itself is not used to determine the length of the cycle.

Shortly after menstruation ends – that is, after the shedding of the uterine lining that developed during the previous cycle under the influence of estrogens – the process of rebuilding the endometrium begins. This process continues until ovulation.

As the endometrium regenerates, the ovarian follicles also begin to grow and mature. Of these follicles, usually only one – called the Graafian follicle – reaches full maturity. The key event of the cycle is ovulation, when the egg is released from the mature Graafian follicle and is captured by the fimbriae of the fallopian tube and guided into its inner portion.

The remains of the ruptured Graafian follicle form the corpus luteum, which produces the hormone progesterone. Progesterone is responsible for transforming the endometrium into a secretory lining. The uterine lining thickens, and its glands secrete large amounts of mucus and glycogen, preparing the uterus for the possible implantation of a fertilized egg.

If fertilization and implantation do not occur, the corpus luteum regresses, progesterone levels decline, and ischemia of the endometrium follows. This leads to shedding of the uterine lining in the form of menstrual bleeding, marking the beginning of a new menstrual cycle.

It is worth noting that the menstrual cycle affects a woman’s entire body. During the first, preovulatory phase, many women experience increased energy, vitality, and a sense of well-being. The second, postovulatory phase is more often associated with reduced physical strength and greater fatigue. Menstruation itself can be seen as a period of renewal – when the body clears, recovers, and prepares to begin the cycle anew.

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The first menstrual cycles are usually single-phase (monophasic) cycles, meaning that only one phase is present and is dominated by estrogen activity. In these early cycles, no rise in basal body temperature is observed and ovulation does not occur, although bleeding may still appear. Most girls during puberty experience so-called withdrawal bleeding, which is caused solely by a drop in estrogen levels, without a corresponding rise in progesterone.

In young girls, estrogen levels are often relatively low, which may result in only slight growth of the endometrium, sometimes insufficient to produce full menstrual bleeding. As a result, the next bleeding may be delayed, or the shedding of the endometrium may occur only in the form of light spotting.

With time, biphasic cycles begin to appear. However, the first postovulatory phases (the higher-temperature phases dominated by progesterone activity) are usually shortened. Bleeding that is preceded by at least three days of elevated temperatures is considered true menstruation. Gradually, the postovulatory phase becomes more regular and typically lasts between 11 and 16 days.

Irregular menstrual cycles in young girls are a completely natural phenomenon. During puberty, the intervals between bleeding episodes may be very short or quite long – sometimes exceeding three months. The individual pattern of the menstrual cycle continues to develop until around the age of 25, and irregular menstruation during this time is normal. Therefore, there is usually no cause for concern – and, importantly, menstrual cycles should not be “regulated” with hormonal pills solely for this reason.

In situations that are troubling or raise doubts, it can be helpful to conduct self-observation – monitoring cervical mucus and basal body temperature – and to record these observations on a cycle chart. This allows one to determine whether cycles are monophasic or biphasic, whether ovulation occurs, whether mid-cycle bleeding is present, and whether there are any other concerning bleeding patterns or signs of hormonal imbalance.

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