Dr Quek Swee Chong
Obstetrician & Gynaecologist
Source: Getty Images and Shutterstock
The menstrual cycle is a term to describe the sequence of events that occur in a woman's body as it prepares for the possibility of pregnancy approximately once every month.
It is also sometimes referred to as the ovarian cycle because it is the ovaries that produce the eggs that are released, which in turn triggers the events of the menstrual cycle.
The menstrual cycle begins on the first day of a period and is on average 28 days long. For some women it can be either shorter or longer, and the range is between 21 – 35 days.
The menses phase starts from Day 1 – Day 5, during which the lining of the uterus sheds out through the vagina if pregnancy has not occurred. In some women this phase can last up to 7 days.
The follicular phase usually take place from Day 6 – Day 14, during which the lining of the uterus thickens due to the production of the hormone oestrogen. In addition, follicles in the ovary start to develop, and from around Day 10 – 14, one of the follicles will form into a mature egg, known as the ovum. The ovary releases the mature egg usually at Day 14 in a 28-day cycle. This phase is known as ovulation.
The luteal phase lasts from Day 15 – Day 28. After ovulation occurs, the egg travels through the fallopian tube towards the uterus. At this time, the lining of the uterus further thickens in preparation for pregnancy. If the egg is fertilised by a sperm and attached itself to the uterine lining, the woman becomes pregnant. If pregnancy does not occur, then the thickened lining of the uterus sheds during the menstrual period.
Signs of an abnormal menstrual cycle include:
Girls usually start menstruating at the average age of 12 but this can be normal from as early as age 8 or as late as age 16. It is normal for girls to have irregular periods during puberty and some girls may take 2 – 3 years before getting a regular menstrual cycle.
Symptoms of a normal menstruation include:
The easiest and best way to track your menstrual cycle is to download an app on your phone. There are numerous apps available and they by and large do a good job of allowing you to input your menses dates and calculate your cycle length, predict your fertile and 'safe' periods.
Menstruation is the release of blood and tissue from the uterus and this is controlled by hormones. Hormone levels change at different stages of life and so it is expected that menstruation and the menstrual cycle changes too.
There are some things like stress and consistent heavy exercise that can affect the menstrual cycle. These can result in missed periods. It is not uncommon for girls to experience a missed period during exam periods, or athletes missing periods when training for competition. Other issues like eating disorders, thyroid disease, post-surgery recovery, antidepressant use and polycystic ovarian disease can also disrupt the menstrual cycle.
Some women who have irregular or painful/heavy periods are sometimes prescribed the oral contraceptive pill (birth control pills) by their doctors. These pills help to regulate the menstrual cycles and reducing the heavy bleeding. In general, they are safe but some women may have contraindications (a specific situation in which this may not be used as it may be harmful to the person), e.g. severe migraines, liver disease or a history thromboembolic disease (blood clots).
The signs and symptoms of menopausal period include:
Women stop having periods when menopause occurs. This is when the ovaries stop ovulating and occurs at about age 51. Menopause is defined as 12 months without a period.
In IVF cycles, drugs are used to stimulate the ovaries to produce more eggs, and some women undergo multiple IVF cycles. However, there is no evidence that this causes early menopause. Once the IVF cycle is complete, the menstrual cycle usually resumes.
Some women experience a change in their menstrual cycle after COVID-19 vaccination. These changes usually affect one cycle and are short-lived, returning to normal thereafter.
There is also no evidence that COVID-19 vaccination has any effect on fertility. These changes are reported in both the mRNA vaccines as well as the adenovirus vectored COVID-19 vaccines. Similarly, around 25% who have had COVID-19 infections also report temporary changes in their menstrual cycle.
It is not yet known whether the temporary menstrual cycle changes are a side effect of the vaccines or due to changes in stress, weight, exercise, etc., all of which are common in the present pandemic.
To address these questions, several large scale studies are being instituted to compare the rates of menstrual variation between vaccinated and unvaccinated women.