WOMEN spend much longer in labour than they did 50 years ago, according to a US study that suggests the causes might include increasing maternal age, weight and changing obstetric practices.

Scientists at the National Institute of Child Health and Human Development compared 39,491 births from 1959 to 1966 with 98,359 births from 2002 to 2008.

All the women initially went into labour without complications.

On average, women in the recent group were 2.5 years older than those in the first. Women giving birth in the 2002-08 group had an average body mass index of 29.9, putting them close to the obese range, compared with 26.3 in the earlier group.

Only 4 per cent of women in the 1959-66 group received epidural anaesthesia, compared with 55 per cent in the recent group. About 12 per cent of the women in the first group received oxytocin to induce labour, compared with 31 per cent in the 2002 group.

A team from the University of Sydney found that epidural analgesia use increased from 17.2 per cent in 1992 to 26.5 per cent in 2003. In 1979, 75 per cent of births were to women under the age of 30. By 1999, births to women younger than 30 had dropped to 52 per cent and by 2009 to 46 per cent, according to figures from the Australian Bureau of Statistics.

The New York Times