How To Calculate Your Due Date With A Due Date Calculator
Congratulations, you're pregnant! Now - when will your new baby arrive?
Congratulations on your pregnancy! No doubt you're full of thoughts of when you can expect to meet your newborn for the first time. Easy peasy! Just use a pregnancy due date calculator!
Did you know there are a number of ways to calculate your due date? We'll tell you all about them. But first, how does a pregnancy due date calculator estimate your due date?
How Does A Due Date Calculator Estimate When Baby Is Due?
Unless you've been tracking your ovulation, there's no way to know for sure exactly when you ovulated and conceived. That's why doctors calculate your due date based on the date of your last menstrual period instead.
Most women ovulate about two weeks after the first day of their period and conceive shortly after. That's 11 to 23 days after your period. Unless you're God or you had an IVF procedure, there's no exact way of knowing when you conceived. The average pregnancy lasts between 37 weeks and 42 weeks. The calculator uses this information to give you an estimated due date.
Types Of Due Date Calculators
The list below contains all pointers to estimating when your baby will arrive. We'll examine them in detail shortly, but they are:
First day of last period
Most pregnancies last around 40 weeks (or 38 weeks from conception). So typically the best way to estimate your due date is to count 40 weeks, or 280 days, from the first day of your last menstrual period (LMP). Another way to do it is to subtract three months from the first day of your last period and add seven days. So if your last period started on April 11, you'd count back three months to January 11 and then add seven days, which means your due date would be January 18. This is how your doctor will estimate your due date — and it’s a pretty solid target. But remember: It’s just as normal to deliver a week or two before or after.
It's quite unlikely for you to remember or know the exact date you conceived, especially if you and your partner have been very busy on the regular. But if you do know, then just add 266 days to your conception date and you have your estimated due date.
IVF transfer date
If you are part of the growing tribe of IVF moms, you can calculate your due date more precisely. Just use the date of your IVF transfer and voila!
Even if you can’t pinpoint when you conceived; forget the day of your last menstrual period, or aren’t sure when ovulation occurred; other clues can help you and your practitioner determine your due date at your first prenatal appointment, including:
An early ultrasound, which can more accurately date the pregnancy. Just be aware, however, that not all women get an early ultrasound. Some practitioners perform them routinely, but others only recommend if your periods are irregular, you're 35 or older, you have a history of miscarriages or pregnancy complications, or the due date can’t be determined based on your physical exam and LMP.
- Pregnancy milestones such as the first time the baby's heartbeat is heard (around week 9 or 10, though it can vary); and when you first feel fetal movement (on average between 18 and 22 weeks, but it can be earlier or later), can give clues as to whether your due date is accurate.
- Your fundal height, which is the measurement from your pubic bone to the top of your uterus, is checked by your practitioner at each prenatal visit and helps confirm your due date.
- The size of your uterus, which will be noted when your initial internal pregnancy exam is performed, can also be a factor in pinpointing the EDD.
Can your due date change?
Yes, your due date can change. While it’s definitely not a reason to worry, your doctor may change your due date for a number of reasons as your pregnancy progresses. It may be that your periods are irregular and your early ultrasound dating was off. Or that your first ultrasound was in the second trimester. It could also be because your fundal height is abnormal. Or your levels of alpha-fetoprotein (AFP), a protein made by the baby, are outside the usual range. Talk to your practitioner if you have any questions or concerns.
Can I plan my due date using a due date calculator?
Whether you're trying to avoid being very pregnant at Christmas or are a teacher who wants to maximize time off with your little one, you can try to time when you conceive in order to "plan" your due date. You may be one of the lucky ones able to get pregnant when she really wants to. Just remember that you probably won't be able to map out exactly when you'll give birth to the day (or even the week or month!).