Pregnancy Due Date Calculator
Tips and methods to calculate your due date. Using your menstrual cycle to calculate your due date. How to calculate your due date using your conception date.
Use this pregnancy calculator to find your due date!
Written by: Nurture&'s team.
Medically reviewed by Gabriela Alvarado.
Medical Doctor from the Central University of Venezuela. She holds certifications in Public Health Practice from institutions such as Johns Hopkins University (USA) and Imperial College London (UK).
From the moment a parent sees a positive pregnancy test, the calculations on when the baby will arrive immediately begin! A visit with your healthcare provider and an ultrasound scan are some of the most accurate ways to determine a baby’s due date. However, there are different tests, methods, and factors that one can use to figure out their estimated date of delivery.
If you are expecting a baby, this article will give you tips on establishing your pregnancy due date. Read on to discover everything you need to know about calculating the date of your baby’s arrival.
Measuring Gestational & Fetal Age
Two standard methods of measuring a baby’s age during pregnancy are gestational age and fetal age. Gestation is the time that passes between conception and birth. To measure the gestational age of your baby, you count the number of days between your last menstrual period and the current date. The gestational age measures how many weeks pregnant you are.
You can calculate gestational age in several ways: ultrasound scan, clinical examination, hCG hormone test, or embryo transfer in the case of IVF. If you’ve undergone IVF, you can determine your baby’s gestational age by counting from your transfer date.
On the other hand, fetal age is the age of your growing baby. It is calculated from the date of conception, which is roughly two to three weeks after the first day of your last menstrual period.
Calculating Your Due Date from Your Last Menstrual Period
Using your menstrual cycle to figure out your estimated due date (EDD) is quite simple! All you need to do is add 280 days from the start of your last menstrual period (LMP). This is referred to as Naegele’s Rule and assumes a 28-day cycle. However, suppose your cycle length varies or is longer or shorter than the average length. In that case, this method may not provide an accurate date.
Another due date calculator that uses the menstrual cycle is the Mittendorf-Williams rule. However, this method is slightly more complicated.
Determine the start date of your last menstrual cycle.
Count back three months from that date.
Add 15 days to that new date for a first pregnancy or 10 days if it is a subsequent pregnancy.
To keep things simple, estimate your due date by using the Nurture& Pregnancy Calculator at the top of this page.
Calculating Your Due Date by The Date of Conception
Calculating your baby’s ETA by the date of conception is slightly more complicated than using your cycle. If you know the date of conception and have a regular cycle, you can add 266 days to that date.
However, the date of fertilization is challenging to pin down and almost impossible to determine. Sperm can live in the body for up to five days, and once ovulation occurs, the egg lives up to twenty hours after release.
Many women, particularly those not trying to conceive, do not even realize they are pregnant until several weeks of pregnancy have passed.
To keep things simple, estimate your due date using the Nurture& Pregnancy Due Date Calculator at the top of this page.
IVF
IVF or in vitro fertilization is an assisted reproductive procedure. During IVF, the mother will undergo egg retrieval, and the eggs will be fertilized in a lab. Once fertilized, one or more embryos will be implanted into the uterus.
Calculating your date by conception is more accurate when parents use in vitro fertilization because your doctor will know the exact date of fertilization.
Ultrasound
Ultrasounds are part of routine obstetrics care. The American College of Obstetricians and Gynecologists states that an ultrasound during the first trimester is not standard prenatal care, but it’s often used to determine:
Gestational age
The number of fetuses
Fetal heart rate
To screen for genetic disorders
To check for ectopic pregnancy
A second-trimester ultrasound is conducted between weeks 18-22 and will confirm gestational age, scan for abnormalities, check the amniotic fluid level, and estimate your baby’s length and weight.
Planning Your Due Date and Planning for Changes
If you are trying to get pregnant, you can attempt to plan your due date for a specific season or time of year. However, there is no way to guarantee when or if you will conceive or when your baby will be born. Very few full-term pregnancies deliver on their estimated date; only 4%!
It is also possible that your due date can change as your pregnancy progresses. This is most likely to occur if you did not have a first-trimester ultrasound. It may also change if your doctor notices your fundal height is abnormal or that your levels of alpha-fetoprotein are high, a sign your baby will be born soon.
The best advice is to expect your baby to arrive a little early or late and give the most accurate health information possible to your provider so they can estimate your due date.
No matter when your baby is expected, having the time frame narrowed down to a few weeks will help you prepare. You will have plenty of time to set up your nursery, complete with Nurture& seating and furniture , a play pad , and comfy pillows.
If you’re attempting to become pregnant or have recently discovered you are pregnant, you can use these tips to calculate your due date and prepare for all the exciting milestones to come!
Sources:
For the due date calculator, the editorial team of Nuture& relied on various reputable sources to ensure accuracy and reliability.
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National Library of Medicine: Naegele's Rule, also known as Naegele's Formula or Naegele's Law, is a simple method used to estimate the expected due date of a pregnant woman. It was developed by the German obstetrician Franz Karl Naegele in the early 19th century.
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National Library of Medicine: Mittendorf-Williams Rule, also known as Mittendorf-Williams Estimated Fetal Weight (EFW) formula, is a method used to estimate the weight of a fetus during pregnancy. It was developed by Dr. Robert Mittendorf and Dr. William D. Williams in 1990 as an alternative to other methods for estimating fetal weight, such as the Johnson-Toshach formula.
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American College of Obstetricians and Gynecologists: Methods for Estimating the Due Date
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American College of Obstetricians and Gynecologists: Ultrasound exams
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Mayo Clinic: In vitro Fertilization
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