The chances of a woman having a baby following IVF go "very rapidly downhill" from the age of 37, according to a study.
The University of Aberdeen study reports a woman's age affects the outcome of every single step of IVF.
Researchers studied data from 121,744 women from across the UK.
They found the chances of having a baby following IVF start to decline by the time the woman reaches her mid-30s, but especially from 37.
The team used data from women who underwent their very first cycle of IVF between 2000 and 2007 using their own eggs.
The research found that even after a pregnancy has been confirmed, women aged 38-39 were 43% more likely to have a miscarriage than women aged 18-34, while women aged 40-42 were almost twice as likely to lose the baby as the younger age group.
Prof Siladitya Bhattacharya, of the Reproductive Medicine team at the University of Aberdeen who led the research, said: "IVF comprises a number of key steps, each of which has to be successfully achieved before the next stage can be attempted.
"We found that age impacted on every single hurdle that has to be overcome during the emotional rollercoaster that is IVF.
"This influence of age is sustained at each stage of the IVF process.
"There is no point during an IVF treatment - even in women who have done well in a preceding stage - when age ceases to matter.
"Age has the capacity to increase the risk of treatment failure even in women who respond to hormonal treatment, have eggs harvested and embryos replaced."
He concluded: "Many couples want to understand how their chances of having a baby evolve over the course of an IVF treatment.
"Previous work has been able to offer a global prediction of success in IVF.
"We hope our study provides a more accurate and dynamic way of predicting a couple's chances of treatment failure as they negotiate each step of IVF."