Understanding Pregnancy Rates

It's important to understand what your chances of success are. At Fertility Associates we have put together a number of pregnancy rates for groups of people undergoing similar treatment or are in similar circumstances.

Stats can be confusing so to start with we have a guide on what you need to look out for or be conscious of when comparing success rates or finding out your chances,

Guidelines to consider when looking at pregnancy rates:

The most important factors affecting pregnancy rate are:

  • Age of the woman
  • The number of embryos transferred in the case of IVF

There are various ways to present pregnancy rates:

  • The chance of a birth from a single completed treatment. We consider a completed treatment as an IVF cycle with egg collection, or a donor cycle with insemination.
  • Some cycles are stopped before IVF egg collection or donor insemination, but when this happens most of the non-drug costs are reimbursed. 
  • The chance of a clinical pregnancy from a single treatment. A clinical pregnancy is the presence of a fetal sac on ultrasound early in pregnancy, so excludes most miscarriages. Clinical pregnancy rates are used for recent data, since it takes at least 9 months to collect birth outcomes. 
  • Cumulative pregnancy rates, which is the overall chance of a birth. For instance, from the use of all the fresh and frozen embryos from an IVF cycle, or from several cycles of treatment. 
  • It can be useful to compare pregnancy rates with treatment with those of fertile people. As a yardstick, we use a birth rate of 20% per month for fertile women 37 and younger.

Important factors when comparing pregnancy rates:

  • Am I comparing like with like - women’s age, number of embryos, clinical pregnancies or deliveries of a child, definition of a completed IVF cycle?
  • Has a large number of treatment cycles been used to derive the statistics? Small numbers can give higher results in some groups just by chance. At Fertility Associates we like to start with at least 500-1000 cycles of treatment.
  • What is the rate of twins and triplets? Many clinics increase their IVF pregnancy rate by transferring more than two embryos.
  • What proportion of people were stopped before IVF egg collection? Fertility Associates patient information booklets give this information. 


Success with IVF at Fertility Associates

The following tables and graphs come from the most recent Fertility Associates patient information.

Success from a single IVF cycle

Birth rate per egg collection by woman's age

The graph below shows the chance of a child from a single IVF egg collection, including the use of any frozen embryos if a fresh embryo transfer did not result in a pregnancy. The data includes all cycles at Fertility Associates clinics between 2010 and 2012, including those where no eggs were collected, but it excludes women using donor eggs since it is the donor's age that is more important in this group.


Birth rate from a single IVF cycle - curve split by AMH level:

We don’t have enough information yet to subdivide anything below 5 pmol/l AMH into smaller steps.

Birth Rate from a single IVF cycle by the number of eggs collected:

People frequently want to know how the number of eggs affects success rate. We have tried to do that in the figure below. Please remember these are averages and that there can be a lot of variation for individuals. Although it would be nice to obtain 11–15 eggs, many women are unable to produce this number no matter what medication dose or method is used. Fortunately, getting fewer eggs still gives a reasonable chance of having a baby.

Success using thawed embryos:

The chance of birth after transferring a thawed embryo is also dependent on the woman’s age, but it is her age when the egg is collected not when the embryo is transferred. The figure below shows data from Fertility Associates clinics for cycles in 2010–2012. Of course, embryos needs to survive freezing and thawing first – survival rates per embryo are around 70% per embryo frozen on day 1–3 of development, but are now around 90% for blastocysts. Identical twins can also occur with frozen embryos, and at about the same rate as with fresh embryos.

Cumulative Success rates:

No one tries to become pregnant naturally and then gives up if it doesn’t happen in the first month of trying – becoming pregnant is a numbers game with overall chance of success increasing each time you try. This is called the ‘cumulative birth rate’. The same applies to fertility treatments like IVF, although of course cost and ‘effort’ set limits for most people. Fortunately, if you do not become pregnant from your first IVF cycle, then the chance of success in the second or third cycles is just as good. It may even be a bit higher if you do become pregnant but miscarry. If you are prepared to try up to three IVF cycles, then your overall chance of having a baby is 80% if you are under 38, as shown in the figure below:

If you are still feeling confused or you would like to know more we do offer:

FREE nurse consults:
A free 15 minute nurse consult where you can ask for personalised information and you have the opportunity to ask a fertility nurse the key things you would like to know about fertility treatment. Click here to find out more 

Pathways Magazine:
Check out our pathways magazine to find out more about fertility treatment at Fertility Associates. Click here to view.

See a Fertility Specialist:
Talk through the options with a specialist: Click here to book an appointment