The Outcome study examines the fate of 4083 patients beginning IVF in 41 IVF centres, between January 2010 and December 2013.

Cumulative live birth rate per patient (CLBR), the best reflection of IVF efficacy, is rarely presented in publications as it requires long-term follow-up, including all successive cycles, and pregnancies outcome.

Analysis of international publications shows an average CLBR of 41.6 % and a drop-out rate of 49.5 %, both greatly varying by country and IVF centres.

Because of the frequency with which patients change centre (8%), the Outcome study distinguishes patients with a past history of IVF in another centre (CLBR=47.2 %) and patients undergoing their first true cycle (CLBR=56.4 %). Survival techniques by Competing Risk, intended to take account of drop-out and lost to follow-up, assessed the overall CLBR as being 65.4 %.

Differences in performance between centres are considerable for both CLBR (32–64%) and Performance Index, taking account of the number of cycles required to achieve a pregnancy (2–5).

Multiple variance logistic regression analysis shows that the indicators influencing performance are age, parity, number of oocytes, smoking habit and overweight. These indicators are independent each other and are influencing performance in a high significant way.

After adjusting for these indicators, the differences between centres are reduced but remain large and very significant. No centre appears to have specific expertise in the management of patients with adverse indicators.

The Outcome study therefore confirms that the large differences in performance between centres are not explained by a difference in the treated population.