Thousands of emergency caesarean sections could be avoided in the UK every year by scanning women in late pregnancy, research by the University of East Anglia and the University of Cambridge suggests.
A routine ultrasound at 36 weeks would help detect babies in breech position, which can lead to complications during labour, according to the study published in journal PLOS Medicine.
Midwives currently check the position of the baby by feeling the mother's bump, but the researchers said an extra scan could save the NHS money and reduce the risk of problems.
The team, from the University of Cambridge and the University of East Anglia (UEA), performed ultrasounds at 36 weeks in 3,879 women in England having their first child.
They discovered breech presentations, when a baby is lying feet or bottom first, in 179 women (4.6%).
In more than half of these cases (55%), a breech presentation had not previously been suspected.
Dr Ed Wilson, from UEA's health economics group, said:
Diagnosing breech presentation at 36 weeks allows a woman to try to turn the baby before the labour, the researchers said.
Professor Gordon Smith, from the University of Cambridge and chief investigator, said:
Hospitals in England offer all women at least two ultrasound scans during their pregnancy, at eight to 14 weeks and between 18 and 21 weeks. Some women are offered more depending on the health of their baby.