Pregnancy Due Date Calculator
Calculate your estimated due date, current gestational age, and pregnancy progress milestones based on LMP, conception date, or IVF transfer.
How a Pregnancy Due Date is Calculated
A typical pregnancy lasts about 280 days (40 weeks) from the first day of your last menstrual period (LMP). Because conception dates are rarely known precisely, doctors and midwives use the LMP as the starting point to estimate when a baby will be born.
Naegele's Rule
The standard formula to calculate a pregnancy due date is Naegele's Rule. It assumes a regular 28-day menstrual cycle. The formula takes the first day of the last menstrual period, adds 280 days, and adjusts for cycle variations:
Alternative Calculation Methods
Depending on your pregnancy details, other methods may be more accurate:
- Conception Date: If the exact date of conception is known, the due date is calculated by adding 266 days to that date.
- IVF Transfer Date: For pregnancies achieved through In Vitro Fertilization (IVF), the due date is calculated based on the embryo transfer date and age (Day 3 or Day 5).
- Ultrasound Scan: Early ultrasound measurements are often the most accurate way to establish or revise a due date, especially for irregular cycles.
Standard Pregnancy Trimester Timeline
Pregnancy is divided into three distinct phases called trimesters. Here is the standard timeline breakdown:
| Trimester | Weeks Range | Key Developments |
|---|---|---|
| First Trimester | Weeks 1 to 12 | Organ development, first heartbeat, hormone fluctuations. |
| Second Trimester | Weeks 13 to 26 | Baby grows rapidly, movements felt (quickening), gender reveal. |
| Third Trimester | Weeks 27 to 40 | Baby gains weight, lungs mature, preparing for labor and delivery. |
Also check: Pregnancy Conception Calculator, Pregnancy Weight Gain Calculator, Fertility Calculator, Age Calculator, Date Calculator, BMI Calculator.
Frequently Asked Questions
How accurate is the estimated due date (EDD)?
Only about 4 to 5% of babies are born exactly on their estimated due date. Most babies are born within two weeks before or after the EDD. It acts as a useful reference timeline rather than a precise prediction.
What happens if my menstrual cycle is irregular?
If your cycle is irregular, calculations based on the LMP may be less accurate. In these cases, doctors rely on dating ultrasounds performed during the first trimester to set the official due date.
Can my due date change during pregnancy?
Yes. If an early ultrasound scan shows that the baby is significantly larger or smaller than expected based on your LMP, your healthcare provider may update your due date.
When is a baby considered full-term?
A pregnancy is considered full-term between 37 weeks and 42 weeks. Delivering between weeks 39 and 41 is associated with the best outcomes for both mother and baby.
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