Women who wait until their 30s to start a family are defying nature and risking heartbreak, say doctors in a stark warning about the dangers of older motherhood.
Three obstetricians from Guy's and St Thomas' Hospitals in London have catalogued the problems - including high blood pressure, diabetes and fetalabnormality - that can befall older women who become pregnant.
Men are also affected because sperm counts decline with age and their children have an increased risk of schizophrenia and genetic disorders.
Many couples wrongly believe they can fall back on IVF if all else fails. But doctors say this "expensive, invasive" treatment has a high failure rate. Seven out of 10 women who have IVF do not achieve a live birth, rising to nine out of 10 over the age of 40.
The obstetricians say in the British Medical Journal: "Women want to have it all, but biology is unchanged ... If women want room for manoeuvre they are unwise to wait till their 30s."
The biologically optimal time for childbearing is 20 to 35, but the age of first motherhood has been rising since the mid-1970s, with the sharpest increases in births to women in their late 30s and early 40s.
And the rate of complications and abnormalities is increasing.
Susan Bewley, consultant obstetrician at Guy's and lead author of the study, says: "If you want a family - and most people want a couple of children - and you are going to complete your childbearing by 35 and leave time for recovery in between, you would be wise to start before 30.
"People are aware ageing is a bad thing but the bio-panic women used to have on their 30th birthday has moved up to the 40th birthday.
"In surveys of older mothers, 50 per cent said they delayed because they had not met a suitable partner.
"Maybe instead of waiting for Mr Right they ought to wait for Mr Good-Enough, if they want children."
Social and psychological benefits of older motherhood were found to be slight compared with the physical risks.
