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How Far Along are You?
A full-term pregnancy lasts approximately 10 lunar months, or 280 days, from the first day of the last menstrual period (LMP). This calculation assumes a cycle length of 28 days. If your cycle is not 28 days, you will do all the calculations from an adjusted LMP date, that is, an LMP date adjusted as if you had a 28-day cycle, then adjust your due date as described below.
How "far along" you are can be calculated in two ways:
1. From the date of your last menstrual period
2. From the date of conception, which typically occurs two weeks after your last menstrual period, which is called weeks from gestation.
An even easier way to determine your due date, is to plug the date of your last menstrual period into our Due Date Calculator.
When is Your Due Date?
The traditional way to calculate a due date is to subtract three months from the first day of the LMP and then add seven days. For example:
- You have a LMP of May 21, 2004 (5/21/04)
- Subtract three months, bringing you to February (2/21/04).
- Add seven days, bringing you to February 28 (2/28/04)
- Then adjust the year to the next year to February 28, 2005 (2/28/05)
- Thus, your due date becomes February 28, 2005 (2/28/05).
Because women get pregnant in all the months of the calendar, some of which have 28, 29, 30 and 31 days, calculation of due dates is rarely precise. As a result, a baby is considered full-term three weeks before the estimated due date (EDD).