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Success Rates Explained

The IVF London guide to understanding IVF success rates,
and how these are calculated


Unfortunately, there are no guarantees with any fertility treatment — even that a cycle will go as planned, not least because the chance of your own success will depend on many factors, including the cause of your fertility problem, your age, weight, lifestyle and how any treatment is carried out. It also depends on how everybody reacts to these treatments, because every ‘body’ is different, which simply reflects your uniqueness.

Because of these factors, IVF success rates can also vary and clinics may choose which rate they publish such as Pregnancy per cycle started (from commencement of stimulation of drugs), Pregnancy per egg collection/retrieval (Cycles that reach an egg collection) ), Pregnancy per Embryo transfer (cycles that reach an embryo transfer) or Pregnancy per embryo transferred as a measure of the success of their IVF/ICSI program.

It is important to understand that not all cycles that start will reach egg collection or embryo transfer. Less than 5% of women would have their cycles cancelled after taking stimulation (Inadequate response to drugs) or after egg collection (no mature eggs/fertilisation or suitable embryos formed)

‘Data pending HFEA verification’

‘Data pending HFEA verification’

Success Rates Page 1

‘Data pending HFEA verification’

Per Treatment CyclePer Egg Collection / RetrievalPer Embryo Transfer
This rate refers to the number of pregnancies among all women who start an IVF treatment cycle, even if they don’t proceed to Egg Collection.This refers to the number of pregnancies among all women who had their eggs retrieved for fertilisation, even if they don’t proceed to Embryo Transfer.This refers to the number of pregnancies among all women who have had fertilised embryos placed back into their uterus, even if they do not become pregnant.
Women commencing IVF stimulation may have their cycle cancelled at this time for the following reasons:
• They may not have produced any or enough eggs for collection after receiving stimulation
• Or, they may have experienced an adverse reaction to the treatment at which point it would be deemed unsafe for them to continue
Those who commence egg collection may have their cycle cancelled at this time for any of the following reasons:
• A woman may have produced too many eggs (hyperstimulation) after taking drugs and it would be deemed unsafe for her to continue the cycle
• The fertilised embryos did not develop normally
• The fertilised embryos test positive during a genetic test
• Or, perhaps no embryos developed
Successful implantation requires a competent blastocyst embryo interacting with a receptive endometrial (uterine) lining to establish a pregnancy, although as in naturally conceived pregnancies, IVF pregnancies may end in miscarriage or loss.
If 10 women commenced a treatment cycle but only 9 have continued to egg collection and embryo transfer, and 5 of those patients had a pregnancy, a clinic would show a 50% success rate Per Treatment Cycle.If 10 women continued their cycle, but only 9 had a successful egg collection and embryo transfer and 5 of those patients had a pregnancy , a clinic would show a 55% success rate Per Egg CollectionIf 9 women had an egg collection but only 7 of those reached an embryo transfer and 5 had successful pregnancies, a clinic would show a 71% success rate per Embryo Transfer

For more information on Success Rates, we recommend you visit

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