Pregnancy Due Date Calculator
- Pregnancy Due Date Calculator can help you work out when you might expect your baby to arrive.
- Pregnancy Due Date Calculator estimates the delivery date of a pregnant woman based on her Last Menstrual Period (LMP), ultrasound, conception date, or IVF transfer date.
- You can check Pregnancy Due Date Calculator by plugging in either the date of your Last Menstrual Cycle or the date you know you conceived. The calculator will do the rest.
- When is your baby due? Use this pregnancy calculator to find your due date based on the date of your last menstrual period, conception date, IVF three-day or five-day transfer date, or date of your last ultrasound.
Steps To Calculate Pregnancy Due Date
- Enter the First Day of Your Last Menstrual Period
- Enter the Average Length of Menstrual Cycles
- Get Your Pregnancy Due Date
How to calculate Your due date?
- There are several ways your due date is determined.
- If you happen to know the day you conceived, you can count 38 weeks from that day to find your due date. (Human gestation takes about 38 weeks.)
- But very few expectant moms know exactly when they conceived. Even if you only had sex once during your fertile period, you wouldn't conceive on that day unless you happen to be ovulating.
- Sperm can live for up to five days inside your fallopian tubes.
- So, it could be up to five days after you have sex that you release an egg (ovulate) and it gets fertilized by a waiting sperm.
- That's the day you conceive.
- So, without knowing the day of conception, how does anyone determine a due date?
First day of your last period
- The most common way to calculate your pregnancy due date is by counting 40 weeks from the first day of your last menstrual period (LMP) and that's how most healthcare providers do it.
- If your menstrual cycle length is the average length (28-day cycle), your menstrual cycle probably started about two weeks before you conceived.
- This explains why pregnancies are said to last 40 weeks instead of 38 weeks.
- This method doesn't take into account how long your menstrual cycle actually is or when you think you might have conceived.
- But generally speaking, women typically ovulate about two weeks after their menstrual cycle starts.
- And women are more likely to know when their last period started than the day they ovulated.
- If you do happen to know precisely when you conceived – say, if you were using an ovulation predictor kit or tracking your ovulation symptoms – you can calculate your pregnancy due date based on your conception date.
- Just choose that calculation method from the pulldown above and put in your date.
Note: Again, you don't necessarily conceive on the day you have sex.
IVF transfer date
- If you conceived through IVF, you can calculate your due date using your IVF transfer date.
- If you had a Day 5 embryo transfer, count 261 days from your transfer date.
- If you had a Day 3 embryo transfer, count 263 days.
This rule is based on a decades-old study that showed that first pregnancies tend to be slightly longer (an average of 288 days from LMP), and for subsequent pregnancies, the delivery date is an average of 283 days from LMP.
- First, determine the first day of your last menstrual period.
- Next, count back three calendar months from that date.
- Lastly, add 15 days to that date if it’s your first pregnancy or 10 days if it’s not your first pregnancy.
How to calculate due date: Parikh’s rule
- Parikh’s rule is another theory that lacks scientific evidence to back it up, so medical practitioners don’t commonly use it to calculate due dates.
- The idea goes, however, that it can help predict due dates in those who have irregular cycles. So, how does it work?
- Loosely designed around Naegele’s rule, the expected date of delivery in Parikh’s rule is calculated by adding nine months to the date of your last menstrual period, subtracting 21 days, and then adding the duration of previous cycles. In short, use this formula:
EDD (Expected Due Date) = LMP + 280 days – 21 days + the average length of previous cycles
How to calculate due date: Wood’s rule
- Wood’s method considers the individual length of the menstrual cycle, as well as the number of pregnancies a person has experienced.
- However, there is also minimal research on this and its effectiveness.
- To work it out First, you calculate your expected due date. Do this using the following formulas.
For first pregnancies
EDD (Expected Due Date) = LMP + 12 months – (2 months and 14 days)
For subsequent pregnancies
EDD = LMP + 12 months – (2 months and 18 days)
Then, you use the expected due date in the equations below.
- For cycles longer than 28 days: EDD + (actual length of cycle – 28 days) = EDD
- For cycles shorter than 28 days: EDD – (28 days – the actual length of the cycle) = EDD
What day did I get pregnant?
- As Doctors explain, it’s hard to predict the exact day you got pregnant (unless you’ve successfully conceived after fertility treatment).
- “It’s all an estimate because it depends on the day you ovulated,”
- If you know your cycle length and it’s always the same, then usually midway through your cycle prior to pregnancy is when conception occurred.”
Can my 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 you have irregular periods 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.
How soon can I take a pregnancy test?
- With all this talk about pregnancy due dates, you may be wondering when you can take a pregnancy test.
- To ensure you get the most accurate reading, it's best to wait a few days after your missed period to take a pregnancy test.
- At-home urine tests measure the amount of hCG (Human Chorionic Gonadotropin) present in your body.
- If you take a pregnancy test before you miss your period, you may not get an accurate result, despite what some tests advertise.
- If you're getting a blood test in your provider's office, you may get results sooner.
- These tests also measure the amount of hCG in your bloodstream, but they're more sensitive than at-home urine tests.
- Blood tests may be able to detect pregnancy six to eight days after ovulation.
Can I plan my due date?
- Nobody ever knows for certain when they will conceive.
- Even if you pinpoint your fertile window and have plenty of unprotected sex during that time, you still won’t know for certain whether or not that will be the month you get pregnant.
- That’s because so much of it is up to chance.
- For context, 45% of young couples (under 35) will conceive after three cycles, and 65% will get pregnant after six cycles.
- So while you might want to plan to have a baby in a certain month, all you can really do is try.
- Some people like to be organized, and there’s nothing wrong with that.
- But it can be quite tricky to plan a due date because there are so many factors at play with the conception that you (and your partner) don’t have control over.
- And even if you do manage to conceive at a time that gives you your ideal due date, remember that your EDD is just an estimate.
- Babies come on their own schedule. While the “average” pregnancy lasts 40 weeks from the day of the last menstrual period, it is normal for babies to come anywhere from 37 to 42 weeks.
- So it’s best not to focus too much on a specific due date.
Other Methods For Estimating the Gestational Age
- A pelvic examination supported by good menstrual records in the first trimester has been reported to be a reliable method for dating pregnancy.
- The fetal heart can be heard using Doppler ultrasound by 10 to 12 weeks in most patients.
- The gestational age should, therefore, be at least 10 to 12 weeks if fetal heart tones are heard.
Human Chorionic Gonadotropin Pregnancy Test
- Human chorionic gonadotropin first becomes detectable in the mother's blood and urine between 6 and 14 days after fertilization (3 to 4 weeks gestational age)
- The gestational age would, therefore, be at least 3 to 4 weeks at the time of a reliable hCG pregnancy test.
- When a twin pregnancy is a result of in vitro fertilization determination of gestational age should be made from the date of embryo transfer.
- Otherwise, to avoid missing a situation of early intrauterine growth restriction in one twin, most experts agree that the clinician may consider dating pregnancy using the larger fetus.
Observed Gestational Age at Delivery
The table below shows the average age of infants delivered in the United States according to the number of fetuses being carried (plurality).
Average Gestational Age (weeks)
- The earlier age at delivery of multiple gestations is a reflection of the increased incidence of preterm labor and obstetric intervention for complications such as preeclampsia, abruptio placentae, fetal growth restriction, and increased risk for stillbirth that occurs as the number of fetuses increases.
- The tendency for multiple gestations to be delivered earlier than singleton pregnancies should not be interpreted as that multiples should be assigned an earlier estimated due date.
- A full-term pregnancy is considered to be 39 to 40 6/7 weeks regardless of the number of fetuses being carried.
Determining the Estimated Due Date
The American College of Obstetricians and Gynecologists recommends that ultrasound-established dates should take preference over menstrual due date change when the discrepancy between ultrasound dating and LMP is
- Greater than 5 days before 9 0/7 weeks of gestation by LMP
- Greater than 7 days from 9 0/7 weeks to 15 6/7 weeks by LMP
- Greater than 10 days from 16 0/7 weeks to 21 6/7 weeks by LMP
- Greater than 14 days from 22 0/7 weeks to 27 6/7 weeks by LMP
- Greater than 21 days after 28 0/7 weeks by LMP
How likely am I to give birth on my due date?
- Of course, a due date calculation is always approximate, whether it's from our tool or from your doctor or midwife.
- Only 1 in 20 women delivers on their due date. You're just as likely to go into labor any day during the two weeks before or after.