Older mothers are being subjected to scans, Caesarean sections and aided deliveries even when these procedures are unnecessary, a hospital study suggests.

Researchers found that doctors viewed birth by older women as high risk, and were more inclined to intervene even if there had been no complications. The report, based on a survey at Aberdeen Maternity Hospital of 28,484 deliveries in nine years, calls on the medical profession to reassess its attitude to older mothers.

First-time mothers at the hospital over the age of 40 were 14 times more likely to have an elective Caesarean than those under 30. Older mothers were more likely to have more than two scans, a stay of more than five days in hospital and to have their baby admitted to a neonatal unit.

John Grant, the editor-in-chief of the British Journal of Obstetrics and Gynaecology, which has published the study, said: "How often has one seen 'elderly primigravida' [first-time mother] written in the special features column of the maternity record? This will convey a subliminal message to the obstetrician and midwife caring for the woman in labour, which will colour their judgements, and lead to a Caesarean section.

"Where there are no tangible medical complications of pregnancy, the risks of childbirth in older women are no greater than in younger women."

The proportion of babies delivered by Ceasarean section has risen steadily in Britain since the 1970s.

Gillian Fletcher, president of the National Childbirth Trust, said doctors making assumptions that all older women would need medical intervention "could become a self-fulfilling prophecy. One should always start from the premise that pregnancy is an entirely normal physiology."

Peter Bowen-Simpkins, consultant obstetrician and spokesman for the Royal College of Obstetricians and Gynaecologists, said: "We probably do intervene more among older women and it is probably unjustified. It is more the worry of the obstetrician than the fact the woman has problems."

Older mothers were more likely to ask a doctor for a Caesarean than younger mothers.