The risk of suffering a miscarriage soars for older mothers, a study suggests.
The number of older mothers has increased in recent decades, as more women concentrate on their career first and turn to family later.
Women now have their first child five years later on average than they did four decades ago.
It means there are now more births to over-40s than to teenagers (in the UK).
But researchers warn that this could be having an impact on complications and miscarriages.
Miscarriage affects one in eight pregnancies - usually occurring before 12 weeks of pregnancy.
A study published in the British Medical Journal found miscarriage rates are lowest among women aged 25 to 29, at 10 per cent.
It rises slightly to 11 per cent among women in their early 30s and to 17 per cent among women aged 35 to 39.
The risk of miscarriage then spikes to 32 per cent among those in their early 40s and 54 per cent over the age of 45.
The research, by the Norwegian Institute of Public Health, involved 420,000 women who became pregant between 2009 and 2013.
They also found a strong recurrent risk of miscarriage - with a woman who had already suffered one miscarriage having a 50 per cent increased risk of a repeat.
After two, the risk doubled, and after three consecutive miscarriages, the risk was four times greater.
Previous pregnancy complications also predicted a higher risk of miscarriage.
For example, if the previous birth ended in a preterm delivery, caesarean section, or if the woman had diabetes during pregnancy, known as gestational diabetes.
But pre-eclampsia, a potentially fatal condition that causes abnormally high blood pressure, in the previous pregnancy was not associated with increased risk of miscarriage.
The researchers wrote: ‘More focused studies of these associations might lead to new insights regarding the shared underlying causes of pregnancy complications and miscarriage.’