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In order to maximise your chances of conception, it is important to have sex during ovulation. There are many methods of sucessfully timing your ovulation cycle.

Your "Fertile Time"

This increases the chances of conception, because it gives the sperm and egg a better chance of meeting. You can use a conception calculator or conception calendar to determine your "fertile time" so that you can plan baby making sex. Conception can only occur around the time of ovulation, and this information can help you increase your chances of pregnancy.

Menstrual period timing (Calendar method)

To determine the length of the menstrual cycle, one only needs to note the date of the beginning of the menstrual period (first day of flow) for two consecutive periods, and then count the day from one date to the next. Keeping track of the length of menstrual cycles will help determine the approximate time of ovulation, because the next period begins approximately two weeks from the date of ovulation.

  • The rough rule to calculate the approximate date of ovulation is : NMP minus 14 days, where NMP is the ( expected) date of the next menstrual period. This is because the luteal phase for most women is 14 days long. Date of ovulation = NMP - 14
  • Keeping track of the menstrual cycle by charting it can indicate other ovulatory disturbances . For example, if a menstrual cycle that is normally 28 days starts to occur every 35 or 40 days, this may mean that ovulation is disturbed, and an evaluation is needed
  • Basal Body Temperature (BBT) chart. During the luteal phase of the cycle, the corpus luteum produces the hormone progestrone, which elevates the basal body temperature. When the basal body temperature has gone up for several days, one can assume that ovulation has occurred. However, it is important to remember that the BBT chart cannot predict ovulation - it cannot tell you when it is going to occur.
The basal temperature chart can be a useful tool. It allows the patient to determine for herself if she is ovulating as well as the approximate date of ovulation, in retrospect. Basal body temperature charts are easy to obtain and the only equipment required is a special BBT thermometer.

Some Instructions

General instructions for keeping a basal body temperature chart include the following :
  • The chart starts on the first day of menstrual flow. Enter the date here.
  • Each morning immediately after awakening, and before getting out of bed or doing anything else, the thermometer is placed under the tongue for at least two minutes. This must be done every morning, except during the period.
  • Accurately record the temperature reading on the graph by placing a dot in the proper location. Indicate days of intercourse with a cross.
  • Note any obvious reason for temperature variation such as colds, or fever on the graph above the reading for that day.

The Limitation 

The major limitation of the BBT is that it does not tell you in advance when you are going to ovulate - therefore its utility in timing sex during the fertile period is small. Interpreting the BBT chart can be tricky for many patients - rarely do the charts look like those you see in textbooks!

Also, keeping a BBT chart can be very stressful - taking your temperature as the first thing you do when you get up in the morning is not much fun. What is worse is that you start to let the BBT chart dictate your sex life. This is why though the BBT chart used to be a useful method in the past, it's utility is limited today - and newer methods are available which are more accurate are available.

The Advances 

Manufacturers have now incorporated a microprocessor along with the digital thermometer, to create an electronic fertility management device, called The Bioself Fertility Indicator. This makes calculation of the "fertile days" much easier, because it combines and optimises both the basal body temperature and calendar method of ovulation prediction.

Free Fertility App

You can download our free fertility app from www.myfertilitydiary.com so you can use your smartphone to help you track your fertile time !

You can also use our free online fertility calculator to determine when you ovulate !


​In order to maximise your chances of conception, it is important to have sex during ovulation. There are many methods of sucessfully timing your ovulation cycle.

Authored by : Dr Aniruddha Malpani, MD and reviewed by Dr Anjali Malpani.

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