';if(method==='5day'){info+='1. 5-Day Blastocyst transfer occurs 5 days after ovulation.
2. Add 261 days to transfer date (266 total days post-conception).';}else if(method==='3day'){info+='1. 3-Day embryo transfer occurs 3 days after ovulation.
2. Add 263 days to transfer date (266 total days post-conception).';}else{info+='1. Ovulation/Retrieval is considered Day 0 (equivalent to CD14).
2. Add 266 days to determine the 40-week due date.';}info+='
Using the Due Date Calculator by IVF
A due date calculator by ivf is a specialized tool used by fertility patients and specialists to accurately determine the expected date of delivery (EDD) after an assisted reproductive procedure. Unlike natural conception, where the first day of the last menstrual period (LMP) is used—which can be inaccurate due to varying ovulation cycles—IVF provides precise "event dates."
By using specific dates like the egg retrieval or the embryo transfer date, this calculator removes the guesswork often associated with gestational age.
- IVF Method Selection
- Choose between a 3-day embryo transfer, 5-day blastocyst transfer, egg retrieval date, or IUI date. Each method adjusts the calculation by a few days to account for the age of the embryo at the time of transfer.
- Procedure Date
- The calendar date when your transfer or retrieval occurred. This is the "Anchor Date" for all subsequent pregnancy milestones.
- Show Pregnancy Milestones
- Check this box to see your "Equivalent LMP" (the date a doctor would record as your last period) and your current gestational age in weeks and days.
How the IVF Due Date is Calculated
Pregnancy is mathematically defined as lasting 280 days (40 weeks) from the first day of the Last Menstrual Period. However, biological gestation is actually 266 days from the moment of conception (ovulation). In IVF, we know the exact moment of conception or embryo age, making the calculation more reliable.
Formula for 5-Day Transfer: EDD = Transfer Date + 261 days
- 3-Day Embryo Transfer: The due date is 263 days from the transfer date.
- 5-Day Embryo Transfer: The due date is 261 days from the transfer date (because the embryo is already 5 days old).
- Egg Retrieval / ICSI: The due date is 266 days from the retrieval date.
- Equivalent LMP: This is calculated by subtracting 14 days from the retrieval date (or 19 days from a 5-day transfer) to align IVF dates with standard obstetric tracking.
Step-by-Step Calculation Example
Scenario: A patient has a frozen 5-day blastocyst transfer on October 10th.
Detailed Calculation:
- Identify Event: 5-Day Transfer
- Identify Date: October 10
- Apply Offset: For 5-day transfers, we add 261 days to the transfer date.
- Mathematics: October 10 + 261 days = June 28 of the following year.
- Equivalent LMP: October 10 minus 19 days = September 21. This is the date you would give a standard OBGYN who asks for your "Last Period."
- Result: Estimated Due Date is June 28.
Common IVF Due Date Questions
Is an IVF due date more accurate than a regular due date?
Yes. Because the date of fertilization or embryo development is known to the hour in a lab setting, IVF due dates are considered the "Gold Standard" of accuracy. Natural conception dates can fluctuate by up to 7-10 days based on when ovulation actually occurred within a cycle.
What if I had a Frozen Embryo Transfer (FET)?
The calculation remains the same for fresh or frozen transfers. The biological age of the embryo (usually 3 or 5 days) is the determining factor, not the time it spent in cryopreservation.
Why does my doctor use a different date?
Some clinics use a standard 40-week wheel which might vary by 1-2 days depending on how they round leap years or month lengths. However, the 266-day post-conception rule is the medical standard used by this due date calculator by ivf.