Regular intercourse is the most important thing before being pregnant. It may be more effective if you can ‘’do it’’ at the right time(when ovulation). At large, women with regular menstruation with general menstruation flow will ovulate. They can predict their fertile period easier than others. Ovulation is roughly estimated as the number of days of the menstrual cycle minus 14 days.
If your period comes once every 28 days, the day of ovulation falls on 28-14=14, the 14th day of your period. If the period comes once every 32 days, the ovulation day falls on 32-14=18, the 18th day of menstruation.
Do people who have irregular periods still ovulate?
Before getting into this topic, we must define what regular menstruation is, then we can define irregular menstruation. “Regular menstruation’’ means your cycle is between 28-35 days and your one menstruation period is between 3-5 days and the amount of blood flow will be around 40ml. (40ml is about two tampons； one pad can absorb 10-20ml) If the menstrual cycle is less than 28 days apart or more than 35 days apart, it means irregular menstruation; or if the interval between periods is different, more than 7-10 days apart, it is also called irregular menstruation.
Some people with irregular menstruation may still ovulate
Therefore, there are several ways to test for ovulation first.
1. Baseline body temperature measurement (22.1% less accurate)
After ovulation, the luteinizing hormone (P4) rises and acts on the hypothalamus, resulting in an increase in body temperature of 0.3-0.6 °C after ovulation. Thus, the basal body temperature will show a biphasic curve in a general ovulation menstruation cycle.
Bioeng Transl Med. 2017 Sep; 2(3): 238–246.
2. Measurement with ovulation test strips (high accuracy)
Luteinizing hormone (LH) levels reach their peak during ovulation and ovulation follows 36 hours later. Therefore, ovulation test strips are used to detect whether the luteinizing hormone in urine has reached its maximum level to determine whether ovulation has occurred.
It is recommended to start using the test strips 3-4 days before the estimated ovulation date, and to test once a day for more than a week. For those who have irregular menstruation, it is recommended to use the shortest cycle to do the estimation and ovulation monitoring.
3. Blood test of progesterone (High Accuracy)
After ovulation, eggs will turn into the corpus and start to secrete progesterone. We can detect the progesterone level to make sure whether eggs release or not. In the middle of the luteal stage, progesterone level in a blood test is >3ng/ml； or at any other time, progesterone level in blood test >5ng/ml show eggs might release.
4. Follow endometrium and follicles by ultrasound (High Accuracy)
Doctors measure the size of follicles and endometrium by transvaginal ultrasonography in order to observe the timing of ovulation and then arrange intercourse to increase the chance of conception. As the follicle grows, it can secrete more estrogens which stimulate the endometrium to be thicker. The endometrium will show a triple-line under ultrasound, now, the average thickness of the endometrium is around 0.8-1.5cm. After ovulation, due to the effect of progesterone, endometrium shows echogenic under ultrasound.
Ref: Bioeng Transl Med. 2017 Sep; 2(3): 238–246.
Table below shows the WHO classification of some common reasons for anovulation:
| Classification of WHO | Hormone Change | Common Cause |
| WHO Type I | Low FSH & LH & E2 level |
1. Hypothalamus or Pituitary gland injury (Surgery、Tumor、Infection、Radiation) 2. Gene defects 3. High doses or long-term use of steroids 4. Pressure 5. Nutritional problem(rapid weight gain or loss) 6.Long-term chronic diseases |
| WHO Type II |
Normal FSH & LH & E2 levels (Androgens may be high) |
It is the most common type of ovarian syndrome, accounting for about 70-80% of cases. Most of them are polycystic ovarian syndrome. They may have low menstrual flow or occasional ovulation. |
| WHO Type III |
(FSH, LH high, E2 low) Low AMH level |
Premature ovarian failure or primary ovarian insufficiency |
| WHO Type IV |
High PRL (prolactin) level Low FSH & LH & E2 level |
High prolactin inhibits gonadotropin release, resulting in low gonadotropin and low estrogen |
If ovulation is not detected by any of the above tests, hormonal tests are usually required. If ovulation is not detected by any of the above tests, hormonal tests are usually required. For example, follicle stimulating hormone (FSH), luteinizing hormone (LH), estradiol, thyroid stimulating hormone (TSH), prolactin, AMH, etc., in order to find out the cause and give the appropriate treatment to achieve the goal of pregnancy as soon as possible.
