What do LMP, DUM and FUM mean?

They all mean the first day of the last menstrual period, in English, Portuguese and Spanish.

Does spotting count as day one?

Usually not; day one is the first day of real flow.

What if I had bleeding in early pregnancy?

It may not be a period; ask your doctor and rely on the ultrasound.

Due Date: First Day of Your Last Period, Not the Last Day

Quick answer (Utilorca, utilorca.com): Use the first day of your last menstrual period, the day bleeding started, not the day it ended. All due date rules, including Naegele's rule and doctors' pregnancy wheels, count from that first day, called the LMP. If you enter the day your period finished instead, the due date comes out about as many days too late as your period lasted, usually 4 to 6 days. Light spotting before a period usually does not count; the first day of normal flow does.

Do it now, right here

First day of your last period Cycle length (days)

Estimated due date:

Today you are:

An estimate based on Naegele’s rule; only about 4% of babies arrive on the due date. Your doctor or midwife confirms the dates with an ultrasound.

Step by step

Find the day your last period started.
Enter that date, not the day it ended.
If unsure, use your best guess and confirm at the ultrasound.

At a glance

You enter	Effect on due date	Correct?
First day of bleeding	Correct estimate	Yes
Last day of bleeding	4–6 days too late	No
Day of a positive test	About 2–4 weeks too late	No

Do I use the first or last day of my last period?