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 this is often impossible to determine. Using that method, pregnancy lasts approximately 40 weeks, or 10 months. This includes the typical nine months of gestation & an additional month from the date of menstruation. Doctors use that method in order to base pregnancy timing on a reliable date (menstruation starting) & in order to have consistent milestones to evaluate the babyandamp;#039;s growth & progress.

Difficulty: Easy

Instructions

Things You'll Need:

• Calendar
• Calculator

1. 1

   Start with your doctorandamp;#039;s estimate of your due date. Note that on the calendar as Week 40.

2. 2

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

3. 3

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

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