The Menstrual Cycle

The menstrual cycle is the process by which a woman’s body prepares for the chance of a pregnancy. The average menstrual cycle is 28 days from the start of one period to the start of the next, but it can range from 21 days to around 35 days.

During the menstrual cycle, the levels of a hormone called oestrogen rise and cause the lining of the uterus to grow and become thicker.  Around the middle of the cycle (approximately day 14 in a 28 day cycle), another hormone called luteinising hormone (LH) rises rapidly.  This is called the LH surge.  The LH surge causes an egg to be released from the ovary (called ovulation) and begins to travel down the fallopian tubes to the uterus. The egg only lives for around 24 hours.  Ovuplan and Ovuplan In-Stream detect the LH surge and are suitable for women with regular periods.

The diagram below shows the rise of LH prior to ovulation and ovulation at day 14 in a 28 day cycle.


If the egg becomes fertilised by sperm and attaches to the uterus, the woman becomes pregnant. Once the fertilised egg attaches to the uterus it begins to produce a hormone called human chorionic gonadotrophin (hCG).  If the egg does not become fertilised, the uterus does not need the extra thick lining and it begins to discharge blood (called period or menstruation).

During the menstrual cycle, there are only about 5 or 6 days per month that a woman can conceive (become pregnant). These days are referred to as the fertile period.  An egg only survives for around 1 day, but sperm can survive for about 3 to 5 days in the vagina and uterus, so if sexual intercourse occurs before a woman is ovulating, she can still become pregnant. 

The time of ovulation differs from woman to woman and can even be different from month to month.  This variability can make it difficult to predict when ovulation will occur as the process of ovulation is complex.  Just dividing the number of days in the cycle in half to pinpoint ovulation is not very accurate and can be quite frustrating, especially in the case of women with irregular cycles. This is where Ovuplan Scope can help identify the fertile period.

The diagram below shows the rise of oestrogen prior to ovulation and the fertile period in a 28 day cycle with ovulation at day 14. 


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