Thread by @firstdoctorr

HOW TO CALCULATE A PREGNANT WOMAN'S DUE DATE

1. Know the first day of your last menstrual period (LMP).

2. Count forward 9 calendar months from the LMP.

3. Add 7 days & 1 year to the date. That's your due date! See examples below...

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If your cycle is normal 28 days, your due date or expected date of delivery (EDD) is around 40 completed weeks.

This is 280 days or 9 months from the first day you saw blood in your last menstruation (i.e. your last menstrual period, LMP)

If your cycle is longer than 28 days, add the difference between your cycle length & 28 days to your calculated date to compensate.

If it is shorter than 28 days, subtract the difference from your calculated date to compensate.

For example;

1. Let's say your LMP was 12 June, 2020.

2. Count 9 calendar months forward from June (which is MARCH!)

3. Add 7 days & 1 year to the date (which is 12+7=19, and 2020+1=2021, respectively).

So your EDD is 19 MARCH, 2021.

However:

If you have a 35 days cycle, you need to add 7 days to your Calculated Due Date, i.e. 7days to 19 March, which is 26TH MARCH, 2021.

&

If you have 21days cycle, subtract 7days from your Calculated Due date, i.e. 7days from 19 March, which is 12TH MARCH, 2021.

Note that you can deliver once your pregnancy is "term" i.e. anywhere from 37 weeks to 42 weeks.

Most women deliver within this range of time.

But people still calculate EDD because most women want a specific date, not a range of time.

NOTE: If the 9 months don't cross to the next year, you won't need to add 1 year to your LMP year.

E.g. if LMP is January, EDD will be October of the same year. But if LMP is June, EDD will be March of the next year.