Calculate estimated conception date based on due date or last menstrual period.
Important information about the conception process and pregnancy dating
The conception date is when the sperm and egg unite to form fertilization. This date typically occurs 24-48 hours after ovulation. In a standard 28-day menstrual cycle, ovulation happens approximately 14 days after the first day of the last period. However, an important point is this: The date of intercourse and conception date can differ. Since sperm can survive in the female body for up to 5 days, if ovulation occurs several days after intercourse, fertilization happens at that time. The egg, on the other hand, only survives for 12-24 hours. Two methods are used to calculate conception date: Subtracting 266 days (38 weeks) from the due date or adding 14 days to the first day of the last period. However, both methods can vary by ±3 days. First-trimester ultrasound examination is the most accurate method for precise dating. Irregular menstrual cycles make these calculations challenging. In such cases, the due date determined by ultrasound measurements is more reliable. Knowing the conception date is important for tracking baby's development and estimating the due date.
About conception date
Subtract 266 days (38 weeks) from due date, or add 14 days to first day of last period for estimated conception date. This assumes a regular 28-day cycle.
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