How do I Determine Date of Conception Based on Missed Period?

The date of conception is the date that an egg was actually penetrated and fertilized by sperm. A woman may want to know this date because she can calculate her due date based on this date. Another reason to want to know this date is to determine paternity if the woman had multiple sexual partners in a short time before she discovered she was pregnant.

Things You'll Need

  • Calendar
  • Pen
  • Highlighter

Instructions

    • 1

      Mark on a calendar the date of the first day of your missed period.

    • 2

      Count backward 14 days. This is the approximate day of conception based upon an ordinary 28-day ovulation cycle. If you cycle isn't 28 days long, then the date of conception will vary.

    • 3

      Highlight three days before the date of conception and three days after. This is the possible week of conception from which your due date can be calculated.

    • 4

      Add 266 days to the approximate date of conception to calculate your due date.

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