How to Determine a Birth Date

Once it has been determined that you are pregnant, it is important to determine the age of gestation in order to monitor adequate fetal growth and development and to figure out the estimates date of delivery (EDD). The date of delivery is estimated using the first day of the last menstrual period (LMP). The EDD is then confirmed with ultrasonographic measures.

Instructions

Estimated Date of Delivery

1. Determine the first day of your LMP.

2. Subtract 3 months from the LMP.

3. Add 7 days to the result of step 2. This is the EDD.

Example

1. My LMP was August 23rd 2010.

2. Subtracting 3 months from LMP gives May 23rd.

3. Adding 7 days to step 2 gives May 30th 2011 as the EDD.

Tips & Warnings

• Prenatal care is very important to the health of your pregnancy. If you think you are pregnant, obtain a prenatal care provider as soon as possible. They will be able to tell you your estimated date of delivery using ultrasonographic measures.

• If your menstrual cycle is not normal, it can be difficult to determine an accurate EDD.

References

• "Current Diagnosis and Treatment: Obstetrics and Gynecology, Ch. 9"; Helene B. Bernstein, MD, PhD, & Milena Weinstein, MD; 2007.
• "Obstetrics: Normal and Problem Pregnancies, Ch. 5"; Timothy R.B. Johnson, MD, Kimberly D. Gregory, MD, MPH, Jennifer R. Niebyl, MD; 2007.

Resources

• Pregnancy Due Dates Calculator