Many couples believe that ovulation occurs close to the 14th day of every menstrual cycle. However, this average of 14th day has lost its relevance in today's world where women undergo a lot of stress in their lives, both at home and office. Actually, the day of ovulation varies significantly between every woman and every cycle and are personal to you. Infact, research has proven that 46% of the menstrual cycles vary by seven or more days .
There are only a few days every cycle when you can get pregnant. These are the days leading upto and including the day of ovulation. The below chart shows the chances of conception on the days of menstrual cycle, relative to the day of ovulation.
The chances of getting pregnant are dramatically increased if you have intercourse in the 6 fertile days leading up to and including ovulation. These days when the chances of getting pregnant are the highest are called the fertile days and are governed by the hormones of the individual.
The fertile days vary between every woman and cycle and can be found out by measuring two key hormone levels (Estrogen and Luteinizing Hormone) in urine. Luteinizing hormone triggers ovulation by surging 24-36 hours before ovulation. Estrogen, a key fertility hormone rises 3-5 days prior and induces the release of Luteinizing hormone.
It is proven that fertility monitors that identify 6 fertile days by measuring two hormones, increase the chances of conception by 89% . Additionally, they also work for women with both regular as well as irregular cycles and reduce the stress in the process of conception.
 Creinin, MD., et al. Contraception (2004) 70: 289-92
 In the first 2 cycles of use. Robinson JE., et al. Fertility & Sterility (2007) 87: 329-334