Guide To Pregnancy Due Date Calculator
If you want to estimate the due date of your conceived baby, we have worked with 3 pregnancy experts to put together a new and very accurate due date calculator. This tool is one of the many that 10BabyGear has been preparing to support pregnant mothers to estimate the likely date of birth for your baby.
There are three ways to estimate the approximate due date period and below are the options:
- Calculating the due date using the last period/conception date
- Calculating the due date using IVF method
- Calculating the due date using Ultrasound
Due Date Calculator on Conception
The date of conception is your day of ovulation as human eggs can only be fertilized in 12 to 24 hours after ovulation. Whether you are using in vitro fertilization or got pregnant naturally, the due date calculator on conception is purely an estimation based on when you ovulated. While the ultrasound estimation method may provide a slightly different conception date, the estimation of the due date may not vary significantly. This above calculator essentially can be called a when to conceive due date calculator
The estimated due date is the date you expect to go into labor and it is calculated using the formula below:
Due Date = (First Day of Last Menstrual Period + 287 DAYS)
The 287 days is the 9 months gestation period for humans plus 7 days. This is not a method specific or developed by the 10BabyGear team. It is a due date calculator and conception date estimator used by pregnancy wheel. You may have seen this being referred to as due date calculator wheel or due date calculator pregnancy wheel.
Both terms mean the same thing, essentially adding 287 days to the last day of your latest menstrual period. This pregnancy wheel calculator of due and conception date has two main assumptions:
- 1st Assumption: That the mother has 28 days menstrual cycle
- 2nd Assumption: That ovulation takes place on the 14th day
This pregnancy wheel calculator is used solely for estimation purposes especially if you don’t remember the last day of your latest menstrual cycle or have forgotten the ovulation date.
Due Date Calculator With In Vitro Fertilization (IVF)
The pregnancy wheel method works perfectly to estimate the expected delivery date when you’re not sure about the day of egg fertilization.
However, if the egg was fertilized using in virto fertilization method, the due date calculator with in vitro fertilization is obtained using the formula below:
Due Date Calculator With In Vitro Fertilization = (Date of Fertilization + 266 Days)
The above formula works if you are having:
- IVF with your own eggs
- IVF with fresh donor egg cycle
- Fresh donor embryos cycles
To arrive at the IVF due date, an IVF due date calculator can use any of the following variables:
- Date of your egg retrieval (Fresh IVF)
- Date of day 3 embryo transfer (Fresh or frozen IVF) or
- Date of day 5 blastocyst transfer (Fresh or frozen IVF)
The IVF due date calculator will give you the estimated date of confinement (EDD)
Due Date Calculator By UltraSound
Ultrasound is the only method among the four we’ve listed in this article that you actually have to visit the doctor. The doctor will use the ultrasound machine to calculate the gestation age and make an estimation of your baby’s due date. The gestation age is the number of days/weeks or months between the first day of your menstrual period and the day the ultrasound test is taken. The American College of Obstetricians and Gynecologists and its Canadian peer have cautioned parents to beware that the due date calculation using the ultrasound method can be inaccurate depending on the gestation age of your fetus. Actually, they recommend specific ultrasound days indicated below:
If you are torn between due date calculator vs ultrasound estimation method, I highly recommend going for due date calculator using conception date to avoid redating the fetus as it may have harmful effects.
The due date calculator according to ultrasound requires you to know the exact gestation age as mentioned above. You’ll then enter the exact gestation age in weeks and days such as 6 weeks and 3 days on the day the ultrasound was performed. I have personally used the due date calculator by ultrasound once during my first pregnancy and I didn’t like it. The process of visiting the doctor, measuring the size of the fetus, estimating the gestation period and comparing the due date calculator vs ultrasound was just too much of hassle to me. The same way I prefer using fetal dopplers/doptones at home to going to see the doctor every other time I want to check my baby’s heartbeat rate.
Is Due Date Calculator Accurate?
To question of whether due date calculators are accurate has been asked by many parents who have been testing the 10BabyGear Pregnancy tool before its release.
There are also several other online due date calculators such as those offered by BabyCenter, the Bump, WhattoExpect and many others. How accurate are all these due date calculators? To determine their accuracy, we carried out a survey with the help of the team at Pregnancy Center to determine the accuracy and below is what we found out
Due date calculators are somewhat accurate and it really depends on the variables you’ve put in. If you are confident about the variables, most due date calculators we surveyed are accurate about 20% of the times.
External studies however disagree and estimate that online calculators are only accurate 5% of the times. For example, if you are not sure about the gestation age, the ultrasound method may not be very accurate and similarly, the due date calculator may return inaccurate results if you don’t know the first day of your latest period.
We have tested and determined that 10BabyGear’s due date calculator is a very accurate calculator available online as of this publication in August 2019. You can, therefore, count on our tool as the most accurate due date calculator available.
Due Date Calculator for Twins
The due date calculator for twins has a minor adjustment compared to regular due date calculators for a single baby. The average pregnancy term for twins is around 38 weeks which is 2 weeks less than the average 40-weeks term for a singletons pregnancy.
If you have twins, you can calculate the due date of your twins using the calculator above and subtracting 14 days from the estimated delivery date.
Due Date Calculator Twins = ( First Day of Last Menstrual Period + 273 Days )
Due Date Calculator for twins IVF
The due date calculator twins for IVF baby follows the same formula indicated below:
Due Date Calculator Twins IVF = (Date of Fertilization + 252 Days)
The four methods above show you how to calculate your due date. As suggested earlier, you can use the tool we’ve prepared for you here at 10BabyGear or you can proceed to try out other tools available online. If you don’t want to use any of the tools, you can develop your own due date calculator excel spreadsheet that will essentially use the basic functions of excel to add up the days and arrive at your estimated due date.
Due Date Calculators Available Online
There are several tools available as of August 2019 and below are the main ones that we reviewed:
- Due date calculator the Bump
- Due date pregnancy calculator by BabyCenter (also has reverse due date calculator by BabyCenter)
- Due date calculator WhattoExpect
Any of the above due date calculators are used by doctors and gynecologists across the US, UK, Europe and beyond.
Due date calculator don’t know last period
If you don’t remember the first day of your last menstrual period(LMP), you can use any day of the week as a variable in the due date calculator above. The due date result you’ll get will have a variation of 7 days and we advise that you go for a reliable estimation by a doctor who can use the ultrasound method to determine the gestation age and the estimated due date without knowing your last period date. If there is no period or the LMP is unknown the ultrasound method is your best chance and we’ve had accurate results with ultrasound when the last period is unknown or when someone missed the period.
Due Date Calculator for Triplets
The average gestation period for triplets is 32 to 35 weeks compared to 38 for twins and 40 for singletons. You should, therefore, plan accordingly to expect your twins earlier than normal, about 5 to 8 weeks earlier.
Frequently Asked Questions on Due Date Calculators
We found that online due date calculators are only accurate 20% of the time and external studies have determined that they are accurate 5% of the times. The variation in the actual delivery date may, however, vary slightly by a few days and maybe the correct term that should be used is due date estimators.
IVF due dates aren’t determined by your last period, the date of conception, or even the egg retrieval day. They are determined by embryo transfer day and the age of the embryo at the time of the transfer. With IVF, the due date is determined by the date that the embryo implants in the uterus.