Written by:

Dr Matt Prior


Dr Matt Prior is a specialist in Reproductive Medicine and Surgery in the North of England. His areas of interest include assisted reproduction, recurrent miscarriage and patient engagement. Matt is a member of the Royal College of Obstetricians and Gynaecologists (RCOG) and is a former member of the RCOG Council.

Issues with ovulation

In this article:

  • Reasons why you might not ovulate regularly
  • Polycystic ovary syndrome (PCOS)
  • The causes of ovulation problems
  • Fertility Testing
  • Ovarian Reserve Testing
  • Planning to get pregnant
  • Main points:

Issues with ovulation

Reasons why you might not ovulate regularly

Women who have long or irregular cycles might not always ovulate. Those with no periods are definitely not ovulating. It is common for girls who have just started periods or women approaching menopause to have irregular cycles, which may or may not be ovulatory.

There are many reasons for irregular or no periods. If you have concerns, I recommend you see your doctor for some basic tests. The first common cause is a change in weight. For example, quickly losing weight or being underweight can stop periods altogether. In fact many female athletes and gymnasts do not have periods. The most common cause affecting 8 out of 10 women with irregular periods is polycystic ovary syndrome (PCOS).

Polycystic ovary syndrome (PCOS)

The most common cause of irregular periods and anovulation (not releasing an egg), is polycystic ovary syndrome (PCOS). This condition affects up to 1 in 5 women. PCOS is diagnosed if there is a combination of irregular periods, an ultrasound scan showing lots of small follicles, or cysts, on the ovaries, and a hormone imbalance which may cause symptoms of male pattern hair growth on the face or abdomen, greasy skin, or spots. The exact cause of PCOS is not known, but it can involve hormone imbalances of high insulin levels and increased conversion of the female oestrogen to the male hormone testosterone.

Normally, each month several small follicles begin to grown and fight it out until one follicle becomes dominant. The other follicles die away and within the dominant follicle an egg matures before ovulation. In PCOS, lots of small follicles grow, but no one follicle wins the fight and so the ovary appears to have lots of larger follicles which look like cysts. This interferes with the cycle causing irregular periods. Occasionally an egg may be released, but this can be haphazard, so identifying when it will occur is problematic.

The causes of ovulation problems

Ovulation problems can be from one of three causes. Firstly, women may have normal ovaries but low messenger hormones from the pituitary gland in the brain, which instructs the ovaries to work. This can arise due to hormone problems, or being underweight. Secondly, women can have ovulation problems due to the ovaries not working properly, most commonly PCOS. Finally, there are women with ovarian failure, where the ovaries have stopped working, which can be due to early menopause or previous cancer treatment.

Fertility Testing

Having regular periods is the best sign that ovulation is happening normally.

To confirm ovulation has occurred in an ongoing menstrual cycle, a progesterone blood test can be taken in the mid-luteal phase of the cycle (day 21 in a 28 day cycle). A rise in progesterone means ovulation has occurred.

Ovarian Reserve Testing

Ovarian reserve decreases with age and these tests are a rough measure of how many eggs a woman has left. Ovarian reserve tests also provide an indication of how well a woman will respond to controlled ovarian stimulation as part of fertility treatment, such as IVF. Ovarian reserve can be measured by two tests: antral follicle count (AFC) or anti-Müllerian hormone (AMH).

Antral follicle count is the number of small follicles in both ovaries detected by ultrasound. Antral follicles are where immature eggs have begun to grow in preparation for upcoming menstrual cycles. These follicles also produce a hormone called AMH which is a good marker of ovarian reserve. Normal levels are between 4 and 50 pmol/l.

Planning to get pregnant

If you’re planning to get pregnant, it is worth following good general health advice. Folic acid supplementation (400 micrograms daily) is recommended to reduce the risk of spina bifida. Next, it is worth keeping a menstrual calendar to make a note of your period dates. This will allow you to know your most fertile period and be helpful in establishing any patterns or irregularity.

Main points:

  • Women who experience irregular cycles may not always ovulate. It’s important for these women to seek help from their doctor, as there can be a few causes of irregular cycles.
  • The most common cause of irregular periods is polycystic ovary syndrome (PCOS). Though the exact cause is unknown, PCOS may be due to a hormonal imbalance.
  • A progesterone blood test may be carried out to confirm if ovulation has occurred.
  • Ovarian reserve testing measures the number of eggs a woman has, which decreases with age.
  • Ovarian reserve can be measured by an antral follicle count (AFC) and an anti-Müllerian hormone (AMH).
  • Keeping a menstrual calendar is a great way of knowing your fertile period and establishing any patterns of irregularity.