It is possible to ovulate earlier or later, even for people with regular menstrual cycles. This can replace the fertile window by a few days in a month. In other words, it is difficult to pinpoint a time in your menstrual cycle where you can be 100 percent guaranteed that you will get pregnant or not.
**Source: पीरियड के कितने दिन पहले प्रेग्नेंट हो सकते हैं **