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Fertile Window - the signs of ovulation
Fertility Gynaecology Obstetrics 

The fertile window is that period of a woman’s menstrual cycle when there is the highest chance of fertilisation to occur. Calculating the fertile window of your cycle may be helpful as you plan a pregnancy.


Understanding your menstrual cycle is essential in calculating your fertile window. An egg survives for about 12 to 24 hours once it is released from the ovary and the sperm survives for about 5 days in the woman’s reproductive tract. The fertile period is calculated based on the day of release of egg/ovum  during the menstrual cycle. On average a woman’s menstrual cycle is generally between 28 and 32 days. Some women have longer and some have shorter cycles. If you have a 28 day cycle, then your ovum is released around day 14 of your menstrual cycle.


To calculate your fertile window, observe your menstrual cycle for a few months and keep a record of how long each cycle lasts. The duration of a menstrual cycle is calculated from the first day of a period to the first day of your next period. Identify your longest and shortest cycle. Now subtract 18 days from your shortest cycle. This is the first day of your fertile window. Subtract 11 days from your longest cycle to get the last day of your fertile window.


There are commercially available ovulation prediction kits which may help you identify the time of ovulation or release of egg/ovum in your body. Apart from that there are small changes in your body during your menstrual cycle which can help you predict the time of ovulation.


  • Tracking your Basal body temperature – Our body temperature can slightly rise after the egg is released and remains high until the start of the next period. This rise in temperature is less than a degree and hence a special thermometer which is sensitive to measure this change should be used. Record your body temperature as soon as you wake up in the morning. Do this at the same time every day. Keep record of your body temperature for a few months and you can see a pattern. Use this to predict the time of ovulation.


  • Observing your cervical mucus – The nature of your cervical mucus changes during each stage of your menstrual cycle. This is due to hormonal changes. A few days before the ovum is released your cervix releases thick mucus. Gradually it becomes less thick, clear and more stretchy as the day of ovulation approaches. The mucus during your ovulation period can stretch for an inch or two when you hold it between your fingers. This is to allow for easy penetration of the sperm. This is an easy method to predict the time of ovulation.


This article is written to be informative and does not substitute seeking a professional consultation from a medical professional.

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