Pregnancy is a happy time. When expecting your little one, you may want to know when he or she was born. Even if it's just an estimate, your due date (HPL) can help you get ready to welcome your baby. In addition, HPL also helps you monitor the growth and development of the fetus. There are several methods for determining HPL, and your doctor can provide a more accurate estimate.
Step
Method 1 of 3: Using an Online Calculator
Step 1. Select the online calculator you want
There are several free options for calculating HPL on the internet. Each calculator provides various features that you may or may not be interested in, such as different ways of calculating HPL and optional reports. You may prefer the calculator provided by your favorite pregnancy site. If you're not sure which one to try, here are HPL calculators that are popular with moms-to-be:
- For a simple option, try Web MD:
- For pregnancy monitoring tips, try What to Expect:
- For pregnancy monitoring and pregnancy facts, try Baby Center:
- For more detailed calculation and reporting options, try Your Due Date:
Step 2. Enter the date of your last menstrual period or the date of conception
Most calculators can provide an HPL based on the date of your last menstrual period or the date of conception. Most women can remember when they last had their period, but determining the exact date of conception is usually not possible.
- Use the date of the first day of your last period.
- Mothers undergoing IVF treatment or using ovulation tracking methods may be able to tell when fertilization occurs.
Step 3. Confirm the date with the doctor
Calculators can provide birth estimates, but you should still see your doctor to check if the calculation is correct. Even though doctors agree, remember that only 5% of babies are born exactly at HPL.
- Online calculators are a way to estimate your due date early in your pregnancy so you can be prepared.
- Later, the doctor can give a clearer picture when the baby should be born.
Method 2 of 3: Calculating Weeks Manually
Step 1. Determine the date of the first day of your last period
Your last period is your period before you get pregnant. The first day of your period represents the first day of your cycle.
- HPL calculations usually use the date of the last menstrual period, not the date of conception because most women do not know when fertilization occurred.
- Fertilization can occur 11–21 days after the first day of the last menstrual period, and sperm can remain in the body for several days after sexual intercourse to fertilize an egg.
Step 2. Count 40 weeks from the date of your last period
The baby will be born 280 days after the first day of the last menstrual period, which is usually 40 weeks. It also represents 10 months, or 10 cycles of 28 days.
Pregnancy usually lasts 37–38 weeks, but is estimated to be 40 weeks because fertilization usually occurs about two weeks after the last menstrual period, which is the date for calculating the HPL
Step 3. Use Naegele's rule as an alternative
You can also calculate your HPL by subtracting three months from the first day of your last period, adding seven days, and then adding one year. The result is your HPL.
- Naegele's rule provides an alternative to calculating HPL that is easier to calculate in your head.
- For example, if your last period started on August 8th, reduce three months to May 8th. If you add seven days, the result is May 15. Your HPL is May 15 next year.
Step 4. Tell your doctor if your periods are irregular
Calculations based on the date of your last period are more accurate for a 28-day cycle. If your cycle is irregular, you may need to wait for an ultrasound from your doctor to determine your HPL.
Method 3 of 3: Using ultrasound
Step 1. Make an appointment with the doctor
As the fetus develops, the doctor will perform an ultrasound to determine the size of the baby. The doctor will be able to see the baby's development better, and also calculate the HPL. Determination of HPL with ultrasound will be more accurate than calculation based on the last menstruation because it is connected with the development of the baby in the womb.
Ultrasound can be done from the 5th or 6th week after the mother's last menstrual period
Step 2. Request an ultrasound examination during the 8th to 18th weeks
This time period is the best time to calculate the HPL by ultrasound. Before 8 weeks, a baby's growth is still difficult to measure. Meanwhile, after the 18th week, the baby's development may vary according to each stage, but this is normal.
Step 3. Wear two-piece clothes that are loose and easy to remove
The doctor will need to attach an ultrasound device to your abdomen to see the baby. You may have to take your clothes off although it can sometimes be just a little unzipped.
For example, you can lift your top to reveal your belly
Step 4. Get ready to take off all your clothes for a transvaginal ultrasound
You will need to completely remove clothing and jewelry that may interfere with the examination process, and the doctor will provide the hospital patient's gown. The ultrasound device will be lubricated and inserted into the vaginal canal to take a close look at the uterus and baby.
- The doctor may perform a transvaginal ultrasound to get a clearer view of the uterus in the early stages of pregnancy. Transvaginal ultrasound is also recommended if there is a high risk of pregnancy or if there are problems with the fetus.
- Your doctor will ask you to empty your bladder just before the transvaginal ultrasound is performed.
Step 5. Drink enough water to fill the bladder
Ultrasound results are usually best when the bladder is full. So, drink plenty of water before going to the doctor. Try to drink up to 8 glasses.
Ask the doctor if you can eat before the ultrasound examination because sometimes it is best for the patient not to eat a few hours before the examination
Step 6. Tell us when your last period was
HPL estimation will be better if the doctor can use the date of the last menstrual period and ultrasound. With these two pieces of information, doctors can determine when the baby will be born with the best accuracy.
Tips
- A normal pregnancy lasts between 38 to 42 weeks. The 40 week estimate is just an average.
- The HPL can change if you are pregnant with twins. Some twin pregnancies do not reach 40 weeks, and the doctor may need to perform an induction based on the development of the fetus.
- Self-calculation of HPL is usually most accurate if your menstrual cycle is 28 days. If your period is irregular, your doctor will provide a more accurate estimate.
