Let’s get ready. “When is my due date?”
We’ll tell you your due date during your prenatal checkup. If you can’t wait until then (and that’s perfectly understandable!), there are easy ways to calculate it yourself in advance. You can use online due date calculators and pregnancy calculators.
Discover why your due date matters and how due date calculators can help you predict the exciting months ahead.
What is a due date?
Your due date, or estimated due date (EDD), is the date a pregnant woman expects to give birth. It’s usually calculated based on the first day of her last menstrual period (LMP), but it can also be calculated based on the fetal date. An ultrasound may be used.
Why is your due date important?
Knowing your due date isn’t just a conversation piece; it’s a crucial part of your pregnancy’s health. “Your due date indicates how far along your pregnancy is at any given point in your pregnancy, which influences the timing of blood tests, ultrasounds, and other tests,”says Dr. Noopur Ghade, obstetrician-gynecologist at Tufts Medical Center.
While your due date doesn’t definitively predict your baby’s arrival, it can help you estimate when your baby is due. “It can help you prepare your home for the birth,” Dr. Ghade says. You can also use your due date to plan childcare, work, travel, and other preparations.
Furthermore, your due date provides the information you need to accurately count down the days until you can finally meet your baby! Structure of the Due Date Calculator
The due date calculator calculates when your baby will be born. There are two ways to calculate this: using your last menstrual period (LMP) or your conception date.
Using your last menstrual period (LMP)
Knowing the start date of your last menstrual period (LMP) before conception can help you calculate your due date. In fact, research shows that an accurate last menstrual period is the best estimate for determining your due date.
However, there is one caveat. This is explained by Salena Zanotti, MD, an ob-gyn at the Cleveland Clinic. Menstruation is considered “regular” if your cycle lasts between 24 and 38 days and ovulation occurs 14 days before your next period. Menstruation that is longer or shorter than this, or that occurs at an unpredictable time each month, is considered irregular.
Irregular periods are common, but if you’re calculating your due date based on your last menstrual period, irregular periods can affect the accuracy of your due date.
Using the Date of Conception
Date calculators can also be used to calculate your due date using your date of conception. If you’ve been keeping track of your most fertile periods during your pregnancy, you may already know your date of conception. This may be accomplished using ovulation calculators, cervical mucus monitoring, basal body temperature measurements, or ovulation predictor kits (OPKs).
However, few people know their exact date of conception, especially if they haven’t recorded their ovulation date. It’s also important to note that the date of conception doesn’t necessarily correspond to the day of intercourse. Sperm can live in the reproductive tract for up to five days, while an egg survives for 12–24 hours, meaning intercourse in the days before ovulation can still result in pregnancy.
Are due date calculators accurate?
Date calculators can’t guarantee an exact date, but they can provide a rough guide. Studies show that only 4% of women give birth on their due date, while approximately 70% give birth within 10 days of their due date.
Date calculators are generally most accurate for women with a 28-day cycle. If you have regular menstrual cycles and know the first day of your last period, due date calculators can be somewhat reliable, says Samuel Campbell, M.D., an obstetrician-gynecologist at Richmond Community Hospital Bonsekull.
On the other hand, if your cycles are irregular, ovulation may not occur as expected, reducing the accuracy of due date calculators. “In these cases, it’s best to confirm your due date with your obstetrician-gynecologist through an ultrasound,” says Dr. Campbell.
Factors Affecting Your Due Date
The accuracy of your due date calculation depends on several factors, including your menstrual cycle, ovulation date, and the length of your pregnancy.
Pregnancy can end prematurely, and the following factors can increase your risk:
- Mother’s age is 35 years or older
- Heavy mother or fetus
- Multiple pregnancies
Medical complications such as preeclampsia, premature rupture of membranes (PROM), gestational diabetes, placental abnormalities, concerns about amniotic fluid volume, and infections
Post-due date
You may give birth past your due date, especially if you are giving birth for the first time. Because post-term pregnancies can have complications such as reduced amniotic fluid volume and large babies, your doctor may recommend an induced labor or cesarean section. Nevertheless, most post-term pregnancies result in healthy babies.
Other Ways to Estimate Your Due Date
Due date calculation tools are just one piece of the puzzle in prenatal planning. To more accurately predict when your baby will be born, they should be used in conjunction with other tools. Here are some other ways to estimate your due date: Ultrasound
An early-trimester ultrasound calculates the estimated gestational age and estimated due date (EDD) of the fetus. “The EDD from the ultrasound is compared with the EDD based on your last menstrual period,” says Dr. Campbell.
After comparing these two values, your healthcare provider can update your due date if deemed necessary. Why might this discrepancy occur? “Ovulation may have occurred a little earlier or later than expected,” says Dr. Gaede.
Additionally, it’s unlikely that your due date will change again after this early-trimester ultrasound.“An ultrasound is the most accurate way to determine your due date,” says Dr. Gaede.
Infertility Treatments, such as In Vitro Fertilization (IVF)
If you’ve undergone infertility treatments, such as in vitro fertilization (IVF), the method for calculating your due date varies. “A reproductive endocrinologist determines your due date based on the date of your IVF procedure,” says Dr. Campbell. This means your due date is based on your embryo transfer date (the date the fertilized embryo implants in the uterus).
How many weeks pregnant are you?
To find out how many weeks pregnant you are, calculate the number of weeks since the first day of your last menstrual period (LMP). For example, if your last period started on April 3rd and it is now May 22nd, you are seven weeks pregnant.