Ovulation – what you need to know
The cervix, which is the bottom part of your uterus, changes quite dramatically during the menstrual cycle depending on the hormones being produced. If you are trying to become pregnant it is important that you understand and recognise these changes so that you can pinpoint the best time to have intercourse in order to conceive.
The cervical canal is lined by mucus-secreting glands. These produce mucus continuously and this mucus undergoes important changes during the menstrual cycle. During the first half of the cycle the mucus is thick and sticky. This has the effect of forming a plug over the cervix, which stops semen from entering. It also makes the vagina acidic, which can kill off sperm within a few hours.
Approximately three to four days before ovulation, levels of the hormone oestrogen build up, the cervical mucus becomes clear and stretchy, and the amount of mucus increases. Sperm can live for up to seven days within this fertile mucus. This fertile fluid turns the vaginal fluids alkaline, which helps to keep the sperm alive and also provides nourishment for the sperm.
Another function of this fertile mucus is that it forms 'swimming canals' through which the sperm can pass quickly. It also acts as a filter allowing healthy sperm to swim forward but effectively trapping abnormal sperm (semen always contains some abnormal sperm) and blocking their passage. Once ovulation has taken place and the level of the hormone progesterone increases the mucus again becomes thick and sticky (infertile mucus) protecting the cervix from sperm.
Checking your fertility
As the egg that you produce during ovulation can only survive for approximately 24 hours and the sperm can live for seven days in alkaline mucus, there is only a small window of opportunity each month in which you can conceive. Some women only produce fertile mucus for a day or two each month so it is important to be able to gauge your fertile time quite accurately. It is easy to have intercourse at the wrong time of the month or not frequently enough at the right time.
You can identify your fertile period yourself by doing the following:
- After passing urine, blot your vaginal mucus with white toilet paper.
- Gently apply a finger to the mucus on the toilet tissue and then pull gently away to test its ability to stretch.
- If it feels slippery like raw egg white, and can stretch between your thumb and finger up to several inches before it breaks, then it is fertile mucus. If it is sticky or crumbly then it is the more acidic infertile mucus. As the mucus changes to fertile mucus it is an indication that ovulation is about to take place.
To take advantage of this window of opportunity, have intercourse on the day you notice that the mucus is stretchy. You should continue to have intercourse every alternate day whilst the mucus remains wet and stretchy. It is important that there is a break of approximately 48 hours between intercourses in order to allow time to maximise the sperm count.
It is important that this method of predicting your fertile period does not take over your lives. It is possible for couples to become obsessed about having intercourse at exactly the right time in order to conceive. This can cause problems, as spontaneity may be lost and so can a lot of the enjoyment of making love.
It is important to be aware that you will not be able to do this test if you have thrush or some other vaginal discharge, as it will not be possible to see the changes in the cervical mucus. Any of these problems should be treated before you conceive.
Taking your temperature
Another way to identify your fertile period is by taking your temperature on a daily basis. Charting your temperature each day will tell you if you are ovulating and when. The temperature rise around the middle of your cycle will confirm that ovulation has taken place. It cannot predict ovulation in advance therefore it is more a way of identifying when you are likely to be fertile in future cycles.
If you have a regular 28-day cycle there should be a temperature rise from days 14-16. It is during the days just before this point that you should be at your most fertile. While using this method you should have intercourse on alternate days from about day 11 to day 16, even if you are unsure whether the vaginal mucus is fertile or not.
The temperature reading must be the basal body temperature and therefore needs to be measured first thing in the morning. Our normal body temperature increases as the day goes on so it is important that you record your temperature at the same time each day. To use this method:
- Take your temperature first thing in the morning before you get out of bed and before you have anything to drink or go to the toilet
- Plot the temperature on a graph to see the changes over the cycle. Use a different graph for each cycle, counting the first day of your period as day one. Since not all women have a 28-day cycle you have to count the actual days to be able to pinpoint the vital days in the months ahead when you are at your most fertile.
If you use this method of detecting your most fertile time, remember that many factors can affect your temperature including shift work, alcohol, travelling across time zones, or illness.
An ovulation kit will enable you to predict your ovulation by measuring the luteinising hormone (LH) surge in an early morning urine sample. This test is done by using a dipstick, which changes colour when the levels of LH rise. When your LH rises it is likely that ovulation will occur within the next 24-36 hours so it is advisable to have intercourse around this time. These kits are available from most chemists and come with full instructions. They are relatively easy to use and the instructions tell you when to start testing depending on the length of your cycle.
If you suffer from polycystic ovary syndrome you should not use these kits, as the results may be misleading. LH levels in women who have this condition are often high, which means that the kit may register as positive whatever time of the month you do the test.