Women who want a family should conceive or freeze their eggs by 35, doctors have said, after a major study showed fertility falling off a "cliff edge" in subsequent years.
The research shows that women trying to have a baby are 18 times less likely to succeed at the age of 44 as when they are just six years younger.
Senior doctors said findings from the study - the largest and most detailed of its kind - showed the need for women who want children to stop delaying motherhood, or putting careers first.
They said there was a need for "more realistic expectations" among many women, who should either start trying for a family earlier or freeze their eggs.
IVF experts said many women had little idea how low their conception chances were.