How to Predict a Due Date Based on LMP
A pregnancy can be a great blessing in one's life, and it's only natural to want to calculate your due date once you learn you are pregnant. By keeping in mind that a normal pregnancy lasts 40 weeks---or approximately 280 days---from the date of your last menstrual period (LMP), you can calculate the arrival date of your new little one. Keep in mind, however, that healthy babies can be born up to 21 days before or after this date, so it is only a prediction.
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Instructions
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Note your first day of your last menstrual period.
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Count 40 weeks from that day.
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Alternatively, predict your due date using what ob-gyns dub "Naegle's rule": Take the first day of your last period, and count back three months. Then add seven days, changing the year as needed.
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Tips & Warnings
An example of Naegle's rule: If the first day of your LMP was April 1, 2010, count back three months to January 1. Then add seven days. The estimated due date is January 8, 2011.
Your ob-gyn can also help estimate the due date based upon your LMP or by taking an ultrasound of the baby in utero.
