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How many weeks pregnant are you?
Typically, pregnancy lasts for about 40 weeks, or 280 days. If you conceive naturally, the estimated due date is usually determined based on the first day of your last period, not from the date of conception. Why is this?
The reason is that most people don’t know exactly when they ovulated or conceived. Someone with a regular 28-day menstrual cycle usually ovulates around day 14.
However, this date isn’t 100-percent accurate, as ovulation can occur earlier or later. This is why a due date is just a rough estimate of the day the baby is likely to arrive.
Due date calculation for IVF pregnancies
In-vitro fertilization (IVF) is the only case in which your health care provider will know exactly when you conceived. Enter this date in the “Date of transfer” field of the calculator.
You can calculate your due date by using different formulas depending on the type of IVF you had. Choose your IVF type in the “Type of transfer” field of the calculator.
This is how Flo’s calculator formulas work based on your IVF type (these formulas are set automatically in the calculator for each option you choose):
- IVF with own eggs (with or without ICSI) — Egg retrieval date + 266 days (or 38 weeks)
- IVF with fresh donor egg cycle (with or without ICSI) — Egg retrieval date + 266 days (or 38 weeks)
- Fresh donor embryo cycle — Egg retrieval date + 266 days (or 38 weeks)
- 3 day FET — Transfer date + 266 days (or 38 weeks) – 3 days (for embryos)*
*Sometimes your embryos’ age is more than 3 days, so it’s important to subtract the exact age of the embryos.
- 5 day FET — Transfer date + 266 days (or 38 weeks) – 5 days (for blastocysts)*
*If the blastocysts’ age is more than 5 days, you need to subtract their exact age.
How accurate are IVF due dates?
Due date calculations may vary regardless of whether you conceived naturally or via IVF. Even with IVF and ultrasound measurements, no due date is a guarantee. It’s just a way to provide a window of time in which you are likely to go into labor.