Calculate Your Conception Month: A Guide Based on Due Date

We always think about pregnancy lasting nine months. From a medical point of view, the timing is calculated a bit differently. Pregnancy due dates are calculated from the first day of the last menstrual period, not from day of conception, as that is often impossible to determine. Using this method, pregnancy lasts approximately 40 weeks, or 10 months. This includes the typical nine months of gestation and an additional month from the date of menstruation. Doctors use this method in order to base pregnancy timing on a reliable date (menstruation starting) and in order to have consistent milestones to evaluate the baby's growth and progress.

Things You'll Need

• Calendar
• Calculator

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Instructions

• 1

  Start with your doctor's estimate of your due date. Note this on the calendar as Week 40.

• 2

  Count backward on your calendar until you reach Week 1. This should be the first day of your last menstrual period.

• 3

  Count two weeks forward to Week 3. This is the estimated date of conception. Most women ovulate and conceive about two weeks from the beginning of the menstrual cycle. This week corresponds to your conception month.