Wonder what EDD in Pregnancy Means?

EDD in pregnancy means the estimated date of delivery, which is the day your baby is likely to be born. The medical term for this date is called the estimated date of confinement (EDC).

But the question is,  "How to calculate a gestational date" Or "How to figure out gestational age?"

The estimated delivery date is an important factor in tracking your pregnancy and preparing for your baby's arrival [1]. Calculating the expected date for delivery involves considering various factors, such as the last menstrual period (LMP) and gestational age (GA).

In this article, we will discuss how you can calculate the EDC — estimated date of confinement. This article also includes the importance of estimated delivery dates for a pregnant woman.

What Is Gestational Age?

Gestational age (GA) refers to how long a pregnancy is, measured in weeks [2]. This calculation starts from the first day of the mother's last menstrual period (LMP), not the actual day of conception.

According to different reports, the average pregnancy lasts about 40 weeks from the LMP [3]. Gestational age by LMP is used to estimate how far along the pregnancy is.

Doctors use gestational age to monitor the development of the baby and compare it with normal growth charts [4]. For example, doctors can use estimated gestational age as a reference in scheduling important prenatal tests and assessing whether the baby is growing properly.

How Long Does Pregnancy Last?

Pregnancy lasts around 280 days or 40 weeks from the first day of your last menstrual period [3] and 1st month pregnancy symptoms. However, it is not a confirmation that the baby will born on the exact expected date.

According to different reports, only about 5% of babies are born on their expected delivery date calculated by LMP [5].

Different studies show that the day you calculate for expected pregnancy is just an estimate, and it's completely normal for babies to be born earlier or later than the expected due date.

Methods For Estimating Gestational Age

There are several ways to figure out the signs of gestational age of a pregnancy. These include:

1. LMP Calculation: The most common and straightforward method is using the LMP pregnancy calculator. To get the week of gestation, count the number of weeks and days since the first day of the last period.
2. Gestational Age Calculator: You can also use a GA calculator to determine the gestational age [6]. This can be calculated with the help of online fetal age calculator tools where you input the date of your last menstrual period to get an estimated gestational age.
3. Ultrasound Scan: Another way to calculate gestational age is through an ultrasound, especially if the LMP is not known or periods are irregular.

An early first trimester symptoms ultrasound scan can give you a more accurate due date by ultrasound. The scan measures the size of the embryo or fetus and helps calculate the fetal age more precisely.

The formula for Calculating the Expected Delivery Date

The expected date of delivery formula depends on the last menstrual period. Naegele's Rule is the most common method for calculating the expected delivery date [7]. This is how to calculate age of gestation by following this rule:

1. Start calculating with the first day of your last menstrual period
2. Add one year to the LMP date
3. Then subtract three months
4. Add seven days to the final number.

Here is an example to elaborate further on Naegele’s Rule. Suppose if your LMP was on January 1st, 2024:

• Add one year: January 1st, 2025.
• Subtract three months: October 1st, 2024.
• Add seven days: October 8th, 2024.

So, your EDD would be October 8th, 2024. This method is very common, but it's important to remember that it's an estimate and actual delivery dates can vary.

How Soon After EDD Can You Deliver?

A majority of pregnant women do not deliver on their exact due date. Even if we follow reports, only about 5% of pregnancies result in delivery on the expected or calculated date.

Most women deliver within two weeks before or after the EDD. Babies born before 37 weeks are considered premature, while those born after 42 weeks are post-term [8].

Benefits of Knowing Expected Delivery Date

Information about the expected birth date provides a sense of readiness and peace of mind. It helps schedule necessary prenatal appointments and track the baby’s development.

Pregnancy EDD means that the parents can plan for maternity leave, set up the nursery, and gather essential items. Additionally, your doctor uses this date as a reference to monitor the pregnancy, identify any potential issues early, and ensure a safe and timely delivery.

Conclusion

The meaning of EDD in pregnancy is the date when a pregnant woman is very likely to deliver the baby. The date is calculated by adding 40 weeks to the last menstrual cycle date.

However, many pregnant women don’t give birth on their expected days. Only 5% of births happen to occur on the expected days or period of gestation. We know this date isn’t a confirmation, but it helps parents plan the important delivery steps, such as prenatal appointments.

Resources Used

1. Edwards, K. I., & Itzhak, P. (2022, October 24). Estimated Date of Delivery. StatPearls - NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK536986/ 
2. Naidu, K., & Fredlund, K. L. (2023, July 24). Gestational Age Assessment. StatPearls - NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK526000/ 
3. InformedHealth.org [Internet]. When your baby’s due date has passed. [Updated 2022 Oct 20]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK279571/ 
4. Grantz, K. L. (2021). Fetal Growth Curves: Is There a Universal Reference? Obstetrics and Gynecology Clinics of North America, 48(2), 281. https://doi.org/10.1016/j.ogc.2021.02.003 
5. Estimating Your Due Date. (2023, March 19). WebMD. https://www.webmd.com/women/estimate-due-date 
6. UpToDate. (n.d.-c). UpToDate. https://www.uptodate.com/contents/calculator-estimated-date-of-delivery-edd-patient-education 
7. Due Date Calculator. (n.d.). Stanford Medicine Children’s Health. https://www.stanfordchildrens.org/en/topic/default?id=due-date-calculator-41-DueDateCalc 
8. Fayed, A., Wahabi, H. A., Esmaeil, S., Elmorshedy, H., & AlAniezy, H. (2022). Preterm, early term, and post-term infants from Riyadh mother and baby multicenter cohort study: The cohort profile. Frontiers in Public Health, 10. https://doi.org/10.3389/fpubh.2022.928037