Due Date Calculator
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Your Estimated Due Date is
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Pregnancy Timeline
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Trimester Chart
A pie chart showing the duration of each of the three trimesters.
How is Due Date Calculated?
Your estimated due date (EDD) is the projected date your baby will be born. While it's called a "due date," it's more of a guideline, as only a small percentage of babies are born on this exact day. The most common calculation methods are:
- Last Menstrual Period (LMP): This is the most common method. The due date is calculated by adding 280 days (40 weeks) to the first day of your last menstrual period. This assumes a 28-day cycle, but our calculator adjusts this based on your actual cycle length.
- Date of Conception: If you know the exact date you conceived, the due date is calculated as 266 days (38 weeks) from that date. This is more accurate but often harder for people to know precisely.
- IVF Transfer Date: For IVF pregnancies, the due date is highly accurate. It's calculated based on the embryo's age at transfer. A 5-day blastocyst transfer adds 261 days, and a 3-day embryo transfer adds 263 days to the transfer date.
What Affects Due Date Accuracy?
Several factors can influence the accuracy of your initial due date estimate:
- Irregular Cycles: If your menstrual cycles are irregular, calculating from your LMP can be less accurate because the timing of ovulation varies.
- Unknown LMP: If you're unsure of the first day of your last period, the calculation will be a rough guess.
- First-Trimester Ultrasound: An early ultrasound is the most reliable way to date a pregnancy. A doctor will measure the baby (crown-rump length) to determine a more precise gestational age and may adjust your due date based on these findings.
Tips for a Healthy Pregnancy
- Take Prenatal Vitamins: Start taking a prenatal vitamin with folic acid even before you conceive to help prevent birth defects.
- Eat a Balanced Diet: Focus on fruits, vegetables, lean protein, and whole grains. Stay hydrated by drinking plenty of water.
- Stay Active: Regular, moderate exercise like walking or swimming is beneficial unless your doctor advises otherwise.
- Get Plenty of Rest: Your body is working hard, so aim for 7-9 hours of sleep per night.
- Avoid Harmful Substances: Steer clear of alcohol, tobacco, and illicit drugs. Limit caffeine intake.
- Attend Regular Prenatal Checkups: Regular visits with your healthcare provider are essential for monitoring your health and your baby's development.
Frequently Asked Questions (FAQ)
How accurate is a due date calculator?
A due date calculator provides a very good estimate, especially when your menstrual cycle is regular. However, it's an estimation because the exact day of ovulation and conception can vary. It's a starting point that your doctor will use and may later confirm or adjust with an ultrasound.
Can my due date change during pregnancy?
Yes, it's common for a due date to be adjusted. Your doctor might change your due date after a first-trimester ultrasound, which measures the baby's size and provides a more accurate assessment of gestational age. This is especially common if your periods are irregular.
What if my menstrual cycle is not 28 days?
This calculator accounts for that! If your cycle is longer or shorter than the average 28 days, the calculator adjusts the due date accordingly. A longer cycle usually means ovulation happens later, pushing the due date back, while a shorter cycle moves it forward.
Can an ultrasound give a more accurate due date?
Yes. An ultrasound performed in the first trimester (up to 13 weeks) is considered the most accurate method for dating a pregnancy. It measures the fetus from crown to rump (CRL) to determine its gestational age and establish a more precise due date.
How is the due date calculated after IVF?
IVF due dates are very precise because the exact date of conception is known. The calculation depends on the age of the embryo at transfer. For a 3-day embryo transfer, the due date is 263 days after the transfer date. For a 5-day blastocyst transfer, it's 261 days after.
What percentage of babies are born on their due date?
Only about 4-5% of babies are born on their exact due date. Most babies are born within a week or two of their due date. A full-term pregnancy can last anywhere from 38 to 42 weeks, so the due date is best thought of as the center of a two-week 'delivery window'.
