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Calculating your "due date"

Note: We know it can be hard for people who are undergoing treatment to see materials and resources for people who are or maybe pregnant in a space designed for those in the middle of their journey. However, the goal for every fertility patient is to get pregnant and we want to ensure that everyone is prepared for whatever comes next, whether that is a failed round or (hopefully) that miracle baby you have worked so hard for.

Calendar for "due date"
Calculating your "due date" is an important way to help monitor fetal development

Your “due date” is the estimated date of when one is expected to go into spontaneous labor. This date is important to know from the start of your pregnancy, as healthcare providers will use this metric to determine the gestational age of a fetus. This is a key piece of information to be used by healthcare providers for scheduling prenatal tests and evaluating prenatal milestones. Knowing how far along you are will allow for your OB-GYN to monitor your progress and evaluate if the fetus is developing appropriately. 


Your EDD (estimated due date) is 280 days from the date of your last menstrual period. While 280 days comes out to 40 weeks, the majority of pregnancies range from 37-42 weeks long, also known as “full term”. Do not stress about the exact date. 96% of newborns do not arrive on their estimated time of arrival.


In this post we will discuss the number of ways to determine your EDD, whether you conceived naturally or via IVF. 


Naegele's Rule:

One of the most commonly practiced ways to determine your due date is what is known as Naegele’s Rule. It is applicable to women with a 28-day regular cycle and ovulation taking place on day 14. The rule is as follows:


  • Determine the first day of your last menstrual period 

  • Subtract 3 months 

  • Add 7 days + 1 year 


For example: Your last menstrual period began on September 9, 2024. Counting back 3 calendar months would be June 9, 2025. Adding 1 year and 7 days would bring you to June 16, 2025, as your estimated due date.


This rule is best for women with 28 day cycles. EDD should be adjusted for women with shorter or longer periods. 


Last Menstrual Period:

Another method for calculating your EDD is adding 280 days forward from the first day of your last menstrual period.


For example: If you last menstrual period began on January 31, 2024, EDD will be November 07, 2024


Again, this is only accurate for people who have a regular cycle. 


Conception Date:

If you are tracking according to your conception date, you should add 266 days from the date you conceived. This is easier to predict if you have a consistent cycle and it is more difficult to pinpoint for women who’s cycles are irregular. Keep in mind that we cannot confirm the exact moment of ovulation, therefore relying on a due date according to time of conception should be done with caution.


Fertility Tip: While the egg released during ovulation is only 24 hours, sperm can live up to 5 days, widening your fertile window. 


Ultrasound:

Today, ultrasound screenings are the most accurate way to determine gestational age and the estimated due date (1). In the first trimester, your provider will order a transvaginal ultrasound. As a pregnancy progresses, they will move on to using an abdominal ultrasound. 


For women who have irregular cycles, a transvaginal ultrasound is a safe way to estimate one’s due date. It measures the size of the fetus to determine the gestational age. Ultrasound monitoring is more reliable than guesstimating with one's last menstrual period.  If there is a discrepancy between one’s ultrasound and date of their LMP, the physician will likely rely on the ultrasound scan. 


IVF:

If you conceived via In-Vitro Fertilization you calculate your EDD based on the date of your embryo transfer and the ‘age” of the embryo. 

  • IVF & Fresh Embryo Transfer: 38 weeks or 266 days from the date of the egg retrieval. 

  • Frozen Embryo Transfer: 

  • Day 3 embryo; add 263 days

  • Day 5 embryo;  add 261 days 


Keep in mind, the estimated due date serves as a general guideline and may vary based on individual circumstances.


Seeking further guidance? :

Our Patient Empowerment Coaches provide 30-minute personalized sessions and weekly check-ins to assist you in navigating every stage of your fertility journey, including determining your due date.


At Grain Fertility, Premium Users have the opportunity to work 1:1 with our dedicated Patient Empowerment Coaches. They will help you prepare for your upcoming consultations with your provider and they will provide resources tailored to your individual needs. Our PEC's are committed to supporting you throughout your fertility journey. You can become a Premium member and take advantage of a risk free two-week trial by signing up today at https://app.grainfertility.com/signup.


Resources:

  1. Naidu K, Fredlund KL. Gestational Age Assessment. 2023 Jul 24. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan–. PMID: 30252256.

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