Menstrual cycle


A menstrual cycle begins on the first day of a period and ends the day before the next period begins. For any woman, no two menstrual cycles are necessarily the same and most women will experience periods that differ in length throughout their reproductive lives. A normal cycle length is between 24 and 35 days. Day 1 of a cycle is considered the day of ‘established’ bleeding. Some women have 1 or 2 days of spotting or very light bleeding before bleeding becomes ‘established’.


When does ovulation occur?


Female fertility depends on ovulation, which is the release of an egg from one of the ovaries. Ovulation usually occurs every month, about 2 weeks before the next period starts. Ovulation means that a single egg, which has ripened in the ovary, is released so it may travel down the fallopian tube to the uterus (womb).

The time of ovulation is most accurately predicted by the amount of a hormone called ‘lutenising hormone’ (LH) in the blood. In most cycles, the level of this hormone suddenly increases (this is called the ‘LH surge’), causing the egg to be released from the ovary approximately 36 hours later.


Ovulation signs


Usually, you will be able to identify some signs of ovulation including:

  • changes in cervical mucous – A few days before ovulation, the mucous discharged from the vagina will become clear and stretchy, sometimes appearing like raw egg white and usually producing a slippery, wet sensation. The last day of this type of mucous is just before ovulation.
  • left or right sided lower abdominal pain
  • increased libido
  • backache
  • breast tenderness
  • occasional mid-cycle bleeding or spotting.

Not every fertile woman will experience these signs.


What is the fertile period of a menstrual cycle?


A pregnancy can occur when a mature or ripened egg is fertilised by sperm  in the fallopian tube. Once it has been released from the ovary, the egg survives for about 24 hours. Sperm may survive in a fertile-type mucous for several days. When the mucous is not fertile, sperm do not survive. Therefore, the fertile time of each cycle is short. To increase the chance of becoming pregnant, a woman should have frequent intercourse in the 2 or 3 days before the time of ovulation, particularly when the ‘fertile type’ mucous is observed.

Ovulation is followed by a menstrual period about 13 days later if pregnancy has not occurred. The bleeding of a period is caused by the shedding of the lining of the womb. The interval between ovulation and a period is usually constant, however in certain circumstances it can vary in length, from 11 to 17 days. The interval from the beginning of a period until ovulation is quite variable so that predicting the day of ovulation by counting the number of days from the beginning of a cycle may be inaccurate.


Related articles


Getting the timing right

Lifestyle changes


Attend a free information seminar
Westmead ButtonWestmead Doctor, IVF clinic
When: Wednesday 28 November 2018
Time: 6pm
Where: Westmead Hospital