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Embryo attrition funnel calculator

Why do numbers drop from eggs to embryos?

Q: Which step matters most?

The one where your numbers fall furthest below your unit’s typical rate. Low maturity points at trigger timing; low fertilisation at sperm or method; low blastocyst conversion at egg quality.

Q: Is uniform loss at every step normal?

Some loss at every step is expected. Uniform heavy loss usually reflects egg quality, which tracks age and is not something anyone caused.

Q: Which step should I ask about first?

The one furthest below your unit's typical rate for your age. If every step is roughly normal and the final number is simply small, the limiting factor was how many eggs you started with — a different conversation from one where a specific step failed.

The whole cycle as a funnel — eggs to mature to fertilised to blastocyst. Where you dropped off is more informative than the final number.

Eggs retrieved

Mature (MII)

Fertilised (2PN)

Blastocysts

These are example numbers. Replace them with yours, then press Calculate.

Example answer

25%

15–30%

Within the range commonly reported across mixed populations.

This is a guide, not a diagnosis. Share the result with your doctor.

Your result on the scale

The ranges this calculator uses. Yours is highlighted.

Your numbers

Everything worked out from what you entered.

Retrieved → mature: 83%
Mature → fertilised: 70%
Fertilised → blastocyst: 43%
Overall: eggs → blastocyst: 25%

What each result means

Your result is highlighted. Your own clinic's advice always comes first.

Your result<15%

High attrition overall. Look at the step-by-step rates above — a single weak step points somewhere specific, while uniform loss usually reflects egg quality.

Your result15–30%

Within the range commonly reported across mixed populations.

Your result30%+

Good overall conversion from eggs to blastocysts.

Where this fits in your journey

The usual order, from trying to conceive to pregnancy. Not everyone needs every stage. This calculator belongs to stage 4.

Stage 4 · you are here

During an IVF cycle

Make sense of the numbers your clinic gives you.

Medicines
→
Egg collection
→
Your embryos

This calculator: Why do numbers drop from eggs to embryos?

Calculators for what comes next

How this is worked out

Exact calculationArithmetic on the numbers you enter. If your inputs are right, this figure is right.

The attrition funnel tracks eggs retrieved through mature, fertilised, and blastocyst stages. Where a cycle dropped off is more informative than the final number: low maturity points at trigger timing, low fertilisation at sperm or method, low blastocyst conversion at egg quality.

About this calculator

?What it tells you

Each step from eggs to embryos. The whole cycle as a funnel — eggs to mature to fertilised to blastocyst. Where you dropped off is more informative than the final number.

✓When to use it

After a cycle that did not work, to find where it dropped off

iWhat you need

Eggs retrieved
Mature (MII)
Fertilised (2PN)
Blastocysts

!What it cannot tell you

Compare each step against your own unit’s figures for your age band.

Common questions

Which step matters most?

The one where your numbers fall furthest below your unit’s typical rate. Low maturity points at trigger timing; low fertilisation at sperm or method; low blastocyst conversion at egg quality.

Is uniform loss at every step normal?

Some loss at every step is expected. Uniform heavy loss usually reflects egg quality, which tracks age and is not something anyone caused.

Which step should I ask about first?

The one furthest below your unit's typical rate for your age. If every step is roughly normal and the final number is simply small, the limiting factor was how many eggs you started with — a different conversation from one where a specific step failed.

Sources

Attrition at each step varies with age and between laboratories. The step rates above are more informative than the overall figure.

In an emergency

If you have any of the warning signs listed here, don't wait for a test result or a calculator. Get help now.

112All emergencies, anywhere in India 108Ambulance

Also call your IVF clinic. Most clinics give an emergency number on your treatment or discharge sheet. Save it in your phone now, before you need it.