Fertility declines naturally with age, and for women the quality and quantity of eggs reduces significantly after the age of 35, meaning a woman’s chances of successful IVF also reduce with age, falling sharply after the age of about 42.
Factors such as body weight, smoking, drinking, and drug use can all influence the chances of getting pregnant, which is why a healthy lifestyle is recommended. The University of Aberdeen has created an online tool that can be used to provide an indication of individual chances of success: w3.abdn.ac.uk/clsm/opis
All IVF clinics in the UK are regulated by the HFEA (Human Fertilisation and Embryology Authority), which records data about IVF success. In 2018, the average birth rate per embryo transferred was 31% for patients below 35 (source: HFEA).
The cumulative effect of three full cycles (round of treatment) of IVF increases the chances of a successful pregnancy to 45-53% (source: NICE). This is why the NICE fertility guidelines recommend that those who have been trying to conceive naturally for two years but have been unsuccessful should be offered three IVF cycles.
Sadly, few couples are offered this opportunity through the NHS, which is why many choose to self-fund their treatment.