Live birth rate

The live birth rate is the proportion of attempts that ended with a baby born alive. It is the fertility statistic that counts the thing you came for, which makes it the most useful one to ask for. It is also always lower than pregnancy figures, so it helps to know which you are looking at.

Where you'll meet it

On clinic websites, in consultations, and in the national registry figures behind both. The same clinic in the same year can accurately publish several different percentages, measuring different things. Every treatment guide on this site quotes live birth rather than pregnancy, which is why the numbers here sometimes look lower than the ones you were shown.

What the number actually counts

A live birth rate is a fraction. Babies on the top, attempts on the bottom. The bottom is where the differences come from, because "attempt" can be defined in several ways.

Per cycle started counts every cycle from the first stimulation injection. It includes cycles cancelled because the ovaries did not respond, cycles where the eggs did not fertilise, and cycles where nothing was worth putting back. Per egg collection drops the first of those. Per transfer drops all three, and only counts the cycles that got as far as an embryo going in. Each step up that list counts from a later point in treatment, so each step raises the percentage.

Per cycle started is the one that answers the question you are actually asking, which is what happens if I begin this. The others answer narrower questions that are useful in their own right, especially to a laboratory.

Clinical pregnancy rate, and why it is always higher

A clinical pregnancy is a pregnancy that has been seen on a scan, usually as a sac with a heartbeat at around six or seven weeks. That is a real milestone. It is not a baby.

Between a clinical pregnancy and a live birth sits miscarriage, which becomes more likely as the age of the egg rises. So a clinical pregnancy rate per transfer is higher on two counts. It counts pregnancies rather than births, and it counts only the cycles that reached a transfer. Put those two together and the figure can be not far off double the live birth rate per cycle started for the same patients. Both are accurate; they are simply different fractions.

A related term, biochemical pregnancy, means a positive blood test that never became a visible pregnancy on a scan. Some clinics report a positive pregnancy test rate, and that is the loosest figure of all.

Implantation rate

Implantation rate is a laboratory measure: gestational sacs seen on a scan divided by embryos transferred. It is a sensible tool for judging how a batch of embryos is performing, and it tells you very little about your chances, because it says nothing about miscarriage or about the cycles that never produced an embryo. If you are given an implantation rate, ask for the live birth figure too.

Why the denominator matters

The cycles that never reach a transfer are worth including. Between eggs that do not fertilise and embryos that stop growing before day five, a meaningful minority of cycles end with nothing to put back, and that share grows with age and with low ovarian reserve. Those cycles cost the same as the ones that work, and a per transfer figure leaves them out, which is why per cycle started is the figure to plan around.

Two more things move a clinic's figures. Which patients it treats, since a clinic seeing many complex cases will have a different average. And how many cycles the percentage is based on, because a small denominator swings wildly year to year.

What the figures on this site mean

Numbers in the treatment guides here are hedged bands from the published registry picture, not from any one clinic. Live birth per cycle started with your own eggs runs at roughly a quarter to a third under thirty-five, falls through the late thirties, and is into single figures by the early forties. Live birth per frozen blastocyst transfer sits at roughly a quarter to a third, tracking the age of the egg at collection rather than your age at transfer. The bands are wide on purpose, because published figures differ by country and by year.

Questions to ask

Ask one sentence at the consultation: is that live birth per cycle started, for women in my age band, using their own eggs? Then ask what proportion of cycles reach a transfer, because the answer tells you a lot about the clinic. A good clinic will answer both clearly.

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