Menstrual Cycle

Natural ovulation cycles

Every month from puberty to menopause, an egg is released from a follicle within one of your ovaries. In natural ovulation, each month your ovary starts to grow several follicles, one of which becomes dominant.

Two hormones are responsible for the development of follicles within your ovaries:

  • Follicle stimulating hormone (FSH), and
  • Luteinising hormone (LH)

The cells in the follicles also produce oestrogen and progesterone. Your hormone levels will rise and fall at different stages of your monthly cycle. If the egg meets a sperm somewhere in your fallopian tube, fertilisation may occur. Once cell division begins, an embryo travels down the fallopian tube to your uterus, where it should implant in the endometrium. This typically happens about seven days after ovulation.

Your pregnancy window

When you get your period, the ovary starts to develop a number of follicles, one of which will become dominant. A follicle is a small fluid-filled sac containing an egg.

Ovulation occurs after about 14 days on average, when the egg matures and is released. The egg can survive for about 8 hours in the Fallopian tube, where it can be fertilised by a sperm.

Your pregnancy window is the fertile time leading up to ovulation and fertilisation.

Once you know your pregnancy window, ensure you have sexual intercourse at least every two days during that time. Sperm will survive and retain fertilising ability for two to three days in the Fallopian tubes.

We don’t recommend using temperature charting as your temperature rises after you ovulate, and you need to have intercourse before ovulation. If you are concerned about your menstrual cycle, we can carry out tests to see what is happening.

When do I know when I ovulate?

Every woman is different, and your cycle may also vary month to month. Typically, an ovulatory cycle will be between 24 and 35 days in length. The time from the start of your period to ovulation could be as short as eight days, or as long as 21 days. The time from ovulation to menstruation is more consistent at 11 to 17 days, with an average of 14 days.

To work out when you ovulate, subtract 14 days from the number of days in your cycle. So if your cycle is usually 28 days, you can expect to ovulate on day 14 (between day 12 to 16). It might be helpful to use a urine ovulation detection test during your pregnancy window.

What causes infertility?

Infertility has been historically defined as a couple not conceiving after 12 months of regular unprotected sexual intercourse. Current data show that most couples will conceive within six months of trying, so best practice now suggests you seek a fertility assessment if you are not pregnant within six months.

Apart from increasing female age, infertility can be caused by problems within the female reproductive system, such as ovulation failure, tubal disease or endometriosis (about 40% of cases), or with sperm (again, about 40% of cases). In at least a third of cases there are both male and female factors causing problems.

Female Reproductive System

Understanding your menstrual cycle
Learn about ovulation cycle tracking 
Female fertility testing