menstrual cycle

Each month during the years between puberty and menopause, a woman’s body experiences a number of changes that are happening in order to prepare the body for a possible pregnancy. These changes are a result of the rise and fall of specific hormones. This series of hormone-driven events is called the menstrual cycle. The most obvious sign of the menstrual cycle is the period. 

In this lesson, we are going to learn about MENSTRUAL CYCLE, and will discuss:

• Woman's reproductive system
• Menstrual cycle
• Phases of the menstrual cycle
• Calculating fertile window
• Hormones responsible for the menstrual cycle
• PMS
• Menopause

Woman's reproductive system

First, let us remind ourselves about the reproductive organs inside a woman's body. It will help us to better understand the menstrual cycle.   

A woman's reproductive system consists of:

• 2 ovaries – where eggs are stored, developed, and released
• the uterus (womb) – this is the place where a fertilized egg implants and a baby develops
• the fallopian tubes – two thin tubes that connect the uterus and the ovaries
• the cervix – the entrance to the womb from the vagina
• the vagina

What is the menstrual cycle?

The menstrual cycle is a series of natural changes in hormone production and the structures of the uterus and ovaries of the female reproductive system that makes pregnancy possible. During each menstrual cycle, an egg develops and is released from the ovaries. The lining of the uterus builds up. If a pregnancy doesn’t happen, the uterine lining sheds during a menstrual period. Then the cycle starts again. 

The average length of the menstrual cycle is 28–29 days, but it isn't the same for every woman. Regular cycles that are longer or shorter than this, from 21 to 40 days, are considered normal.

The first menstrual cycle in a woman's life is sometime during puberty. Puberty is the time in life when a boy or girl becomes sexually mature. It is a process that usually happens between ages 10 and 14 for girls and ages 12 and 16 for boys.

The time when a woman stops having a menstrual cycle and is no longer able to get pregnant naturally is called menopause. Periods usually start to become less frequent over a few months or years before they stop altogether. Sometimes they can stop suddenly. Menopause usually occurs between 45 and 55 years of age.

Phases of the menstrual cycle

When planning pregnancy, it is of huge importance to know when during the menstrual cycle is possible to get pregnant. You can not get pregnant on each day of the menstrual cycle. Let us understand this. 

The menstrual cycle is divided into four phases. They are:

• Menstruation
  
  Menstruation is also known by the terms menses, menstrual period, cycle, or period. Menstruation is the regular discharge of blood and mucosal tissue from the inner lining of the uterus through the vagina. It is simply normal vaginal bleeding that lasts few days. 
   
• Follicular phase
  
  The follicular phase is the stage of your menstrual cycle when your body is preparing to release an egg. Actually, the first half of your menstrual cycle is called the follicular phase. It starts on the first day of menstruation and ends when ovulation begins. It is simultaneous with the menstrual phase, but the menstrual phase is shorter. 
   
• Ovulation
  
  Each month one egg (in some cases two or more) is released from the ovaries. Women are born with all the eggs they are ever going to have, and they don't make any new eggs during their lifetime. Ovulation is the process in which a mature egg is released from the ovary. Those six days are important because the egg is able to be fertilized for about 12 to 24 hours after it's released. The few days surrounding ovulation (from approximately days 10 to 18 of a 28-day cycle), constitute the most fertile phase.
   
• Luteal phase
  
  The time between ovulation and before the start of menstruation, when the body prepares for a possible pregnancy is called the luteal phase. This is when fertilization and implantation can happen. This part of the menstrual cycle lasts between 10 to 16 days, depending on the woman. At the end of the luteal phase, one of two things will happen, either your period will start, or you are pregnant. If pregnancy occurs, a woman does not continue to ovulate and will not have a period. If vaginal bleeding is present during the pregnancy, it is not because of the menstrual cycle. Then, there might be some issue or some normal bleeding for which the woman should consult a health professional. The period comes back when the woman is not pregnant anymore. A missed period is usually the first most important sign of pregnancy.

 

 

How to calculate fertile window?

The 'fertile window' is the day an egg is released from the ovary (ovulation) and the five days beforehand. Knowing when in the menstrual cycle a woman is most likely to conceive can increase the chance of pregnancy. When you know your average menstrual cycle length, you can work out when you ovulate. Ovulation happens about 14 days before your period starts. If your average menstrual cycle is 28 days, you ovulate around day 14, and your most fertile days are days 12, 13, and 14.

Hormones responsible for menstrual cycle

The key hormones involved in menstruation are estrogen and progesterone. They are produced by the ovaries. Also, the luteinizing hormone and follicle-stimulating hormone, that are produced by the pituitary gland, under the influence of hormones secreted by the hypothalamus.

In each menstrual cycle, rising levels of the hormone estrogen cause the ovary to develop and release an egg. The womb lining also starts to thicken. This happens during the first half of the cycle. In the second half of the cycle, the rise of the hormone progesterone helps the womb to prepare for the implantation of a developing embryo. 

What is PMS?

Premenstrual syndrome (PMS) is a combination of symptoms that many women get about a week or two before their period. Most women say they get some premenstrual symptoms, such as bloating, headaches, and moodiness. Other premenstrual symptoms include: 

• feeling upset, anxious, or irritable
• tiredness or trouble sleeping
• tummy pain
• breast tenderness
• spotty skin

PMS appears to be caused by rising and falling levels of the hormones estrogen and progesterone, but it is not clear why some women develop it while others don't, but it is possible because some women are more sensitive to hormone level changes than others. 

Menopause

And just like we said, the menstrual cycle does not last forever. The time when a woman stops having a menstrual cycle and is no longer able to get pregnant naturally is called menopause. In menopause periods usually start to become less frequent over a few months or years before they stop altogether. Sometimes they can stop suddenly. Menopause usually occurs between 45 and 55 years of age.

If menopause starts before the age of 40, it is considered premature menopause. Early menopause can happen naturally if a woman's ovaries stop making normal levels of certain hormones, particularly the hormone estrogen. Also, it can be induced by some medical treatments such as surgery or chemotherapy. Women who experience early or premature menopause may need hormone therapy to reduce the risk of diseases such as osteoporosis and cardiovascular disease.

Most women will experience some symptoms around menopause, with differences in the duration and severity. On average, most symptoms last around 4 years from your last period. Symptoms include:

• hot flushes
• difficulty sleeping
• headache
• night sweats
• low mood
• anxiety
• memory and concentration issues
• palpitations
• reduced libido
• chills

Menopause is diagnosed after you've gone 12 months without a menstrual period.

Key points

• The menstrual cycle is the monthly series of changes a woman's body goes through in preparation for the possibility of pregnancy.
• The average length of the menstrual cycle is 28–29 days.
• The first menstrual cycle in a woman's life is sometime during puberty.
• The menstrual cycle is divided into four phases: menstruation (period), follicular phase, ovulation, luteal phase. 
• The key hormones involved in menstruation are estrogen and progesterone.
• The 'fertile window' can be calculated and this info can increase the chance of pregnancy.
• Premenstrual syndrome (PMS) is a combination of symptoms that many women get about a week or two before their period.
• The time when a woman stops having a menstrual cycle and is no longer able to get pregnant naturally is called menopause and is diagnosed after a woman doesn't have a menstrual period for more than 12 months.