Ovulation and the egg cell - 7 amazing facts.

FACTS

In younger women, better quality eggs are released.

Each woman is born with around 2 million prepared ova, and the number will steadily decrease. By puberty, about half a million will remain, and this pool will never increase. Each cell is enclosed in its own follicle, from which, each menstrual cycle, the woman's body selects a few or a dozen follicles to begin developing. The follicles in the ovaries are initially very small and grow at a rate of one or two millimetres per day. Eventually, nature will usually leave only one of them (the Graaf follicle) which will grow further to release a mature egg.

When a woman is young, the body will mostly select those follicles that contain the healthiest egg. As the years go by, fewer and fewer follicles remain and they are of poorer quality. This means that abnormalities, e.g. of chromosomes, may be more frequent in the egg cells. For this reason, women over the age of 35 have more difficulty getting pregnant and a greater risk of having a child with a genetic defect.

The egg cell decides which sperm is allowed in.

A new study by researchers at Stockholm University and Manchester University NHS Foundation shows that it is the egg cell that decides which sperm will fertilise it. This discovery overturns the long-held belief that it is the fastest and strongest sperm that wins the race to the cell. The team claims that there is a chemical communication that takes place between the oocyte and the sperm. Chemicals are released from the ovum and enable it to make a choice. With these substances, the ovum can speed up the run of the selected sperm .

Women are born with a fixed number of egg cells.

Girls are born with all the egg cells they will have throughout their lives and constitute her ovarian reserve. However, there is no single answer to the number of follicles in a woman's ovaries at birth, as this is an individual issue. It is estimated that a woman may have up to 2.5 million oocytes at birth. The oocyte pool cannot be changed in any way, as it is genetically determined.

Stress can inhibit ovulation.

The hypothalamus regulates the pituitary gland, sending it the correct hormonal information, which then secretes hormones to stimulate the ovary to work. Stress significantly affects the production of hormones in the body. In situations of excessive stress, the secretion of cortisol, known as the stress hormone, increases. This causes a chain reaction starting in the hypothalamus. The hypothalamus produces less hormones that control the pituitary gland, which in turn controls the ovary less well. Disruption of this hormonal connection can delay or even prevent ovulation, a symptom of which will be irregular periods. Excessive cortisol production also reduces the production of oestrogen and testosterone. Stress also increases the concentration of prolactin, another hormone whose excess can inhibit ovulation. Thus, stress adversely affects ovulation

MYTHS

Whenever there is menstruation, there is ovulation.

Is ovulation always after a period? When ovulation occurs and fertilisation does not take place, menstruation occurs, but conversely, not necessarily. Sometimes there is a phenomenon called an unbroken ovarian follicle. In this case, the ovum does not leave the follicle, but oestrogen has been produced, so that the endometrium is prepared for pregnancy. Because pregnancy does not occur, menstruation does occur, but it may occur later than a woman might expect.

It is not possible to become pregnant during menstruation.

A common myth about fertility is that a woman cannot get pregnant when she has her period. Although the chances of conceiving are lower during these days, they are not zero. It depends mainly on the length of the cycle, the length of the period as well as the viability of the sperm. Usually when the cycle is 28-30 days long, the bleeding will have time to stop before ovulation occurs. Remember that although ovulation itself, i.e. the time when the ovum is released and ready to be fertilised, lasts 12 to 48 hours, the fertility window is 5 to 7 days, also due to the long life of the sperm. The sperm can therefore 'wait' in the fallopian tubes for the egg to be released. For this reason, in women with short cycles as well as long periods, fertile days can start as early as the end of menstruation.

Ovulation occurs mid-cycle.

Ovulation usually occurs 14 days before menstruation, but phase I of the cycle, the time between the end of menstruation and ovulation, can lengthen or shorten - hence the different cycle lengths. If a woman menstruates every 28 days, ovulation will actually occur mid-cycle. Ovulation can also occur within four days before or after the middle of a woman's menstrual cycle - depending on the length of the cycle. If, like many women, you don't have a 28-day menstrual cycle, keeping a diary on, for example, a smartphone app or ovulation monitor will be helpful in identifying ovulation. This way, you will make regular notes of your menstrual dates, temperature measurements, body symptoms or ultrasound results.

Substantive consultation:

Kajetan Piatkowski, MD - Specialist gynaecologist-obstetrician