Women with a regular cycle of 26-28 days are ovulating (90%). However, most women sometimes are 2-3 days late. In such cases, when the cycle is slightly irregular (e.g. a 28-day cycle followed by a 31-day cycle and then by a 29-day cycle) it is more difficult to determine whether ovulation occurs. Women with cycles of more than 35 days or of less than 25 days usually do not ovulate (or ovulation occurs 1-2 times a year).
One can usually distinguish between a normal ovulatory cycle and a non-ovulatory cycle as follows: an ovulatory cycle is regular (e.g. every 28 days) with normal blood flow. A non –ovulatory cycle is longer than 35 days, usually with heavy and painless bleeding.
Methods to control ovulation
There are several methods to determine fairly accurately when ovulation occurs. Some of them can be applied at home, but for some others it is necessary to visit the doctor.
Cervical mucus test
About 1 day before ovulation, cervical mucus is clear, thin and stretchy. This test is not very accurate. Some women do not produce a lot of mucus, however they ovulate with no problems. The production of mucus is a good sign in order to calculate the next ovulation. It lasts 10-24 hours. After ovulation, when progesterone levels increase, mucus becomes less clear (i.e. white) and less stretchy.
The most reliable method for determining the exact day of ovulation is the LH urine test (LH is detected 36 hours prior to ovulation). There are several urine tests available in the pharmacies so that a woman can examine LH levels in the urine starting from day 9 of her cycle.
In most women the LH surge is detected early in the morning, so a woman can take the test when she wakes up in the morning. If the test is positive (the LH surge is detected), she should have intercourse on the same, as well as on the following, day. This test is very reliable and can prove that the woman is ovulating with an accuracy of up to 90%. The advantage of this test is that it is easy to use, simple and reliable.
Normally, a sonogram on the 9th day of the cycle would reveal a follicle with a diameter of 12-15mm approximately (in a woman with regular ovulatory cycles). This follicle grows 1-2mm / day until it exceeds 18mm in diameter. Then the egg is released, i.e.ovulation occurs, usually on day 12 -14 of a normal cycle.
In some cases, even if the follicle grows normally, ovulation does not occur due to insufficient LH or to other problems. The follicle either continues to grow until it becomes a cyst or it does not break and then starts to shrink.The advantage of the sonogram is that ovulation is detected and proven. Every woman trying to conceive should perform this test at least once, in order to verify that ovulation occurs normally.
Progesterone and LH hormones are responsible for ovulation. The LH surge prior to ovulation makes the follicle break and release the egg. After that, the follicle produces progesterone. Progesterone levels rise for the next 7 days. Peak level is detected 7 days following ovulation. If the egg is fertilised during this cycle, progesterone levels keep rising. We can determine ovulation by measuring progesterone levels in the blood on day 21 of the cycle (in a 28-day cycle).
In women with shorter or longer cycles, progesterone should be tested 7 days before their expected period. For example, a woman with a 32-day cycle should measure progesterone on day 25.
Progesterone levels of 15mg/ml or more are considered normal. However, they not provide sufficient proof that ovulation occurs normally, maybe due to progesterone being produced even when the follicle does not release the egg.
Another easy way to confirm ovulation is to measure a woman’s temperature. This test requires that a woman takes her temperature daily during her cycle. In women who do not ovulate, the temperature is steady during the first days of the cycle; 24 hours before ovulation, there is a slight decrease (0.1 – 0.2 degrees) followed by an increase on the next day (0.2-0.3 degrees). In a normal ovulatory cycle, the temperature is elevated for a few days as an effect of progesterone, the hormone that is responsible for ovulation.
A woman should take her temperature every day in the morning, placing a thermometer in her mouth for 3 minutes. The measurement should be performed before any other activity, as even brushing her teeth may affect her temperature.
Unfortunately, this method is not considered reliable. Another disadvantage is that ovulation is detected the day after it occurs. However, it is very easy and simple. Any woman who wants to learn more about her ovulation can take her temperature for 6 months.