UK researchers found that obese pregnant women were 3.5 times more likely to require a caesarean than pregnant women of a normal weight.
They believe that the high cholesterol levels found in obese pregnant women could weaken the strength of contractions during labour, ruling out a natural delivery.
The researchers propose that giving statins to obese pregnant women could prevent thousands of caesareans each year, but no studies have been conducted to prove this.
Around 150,000 caesareans are carried out each year in England and Wales, and more than half are carried out as an emergency.
What is the research?
The reports are not based on any new research, but on a study published in 2007, and the announcement by the researchers of plans to test statin use in pregnant women.
The researchers carried out a retrospective analysis of women who gave birth at Liverpool Women's Hospital in 2005.
A total of 3,913 pregnant women were identified, 566 of whom were obese, 1,106 overweight, 1,879 of normal weight and 363 underweight. The average age of the women was 29.
Overall, 17.8 per cent of the obese women had an emergency caesarean, compared with 13 per cent of normal weight women. After controlling for other risk factors such as smoking, obese pregnant women were found to be 3.54 times more likely to have an emergency caesarean than women of a normal weight.
Additionally, the researchers collected samples of uterine muscle biopsies from 24 normal weight women and 28 obese women who had undergone an emergency caesarean.
The researchers found that the biopsied muscle samples from the obese women contracted less frequently and with less force than the muscle samples from the normal weight women.
What do the researchers say?
Lead researcher Professor Sue Wray, head of physiology at the University of Liverpool, said: 'We suspect that high cholesterol levels in an obese woman's bloodstream prevent sufficient levels of calcium from entering the uterus muscles which reduces the number of contractions.
'This means that it is not possible to have a normal delivery, so an emergency caesarean is required.'
Giving statins to pregnant women in their final trimester could help to reduce the number of caesareans, said Professor Wray.
Statins are cheap and available on the NHS so they could be an attractive option for obese pregnant women, she added.
'We now hope to investigate giving statins to obese women in the final stages of pregnancy,' she said.
What do other researchers say?
But Dr Sarah Jarvis, RCGP spokeswoman for women's health and a GP in West London, said: 'There have been no studies on the use of statins in pregnant women so we cannot recommend that pregnant women take them.
'GPs should instead encourage pregnant women to follow a healthy diet to lower their cholesterol levels.'
BJOG 2007; 114: 343-8
- Obese pregnant women are 3.5 times more likely to require an emergency caesarean than a pregnant woman of a normal weight.
- High cholesterol levels reduce the number of uterine muscle contractions.
- Statins have not yet been tested in pregnant women.
- GPs should advise pregnant women to follow a healthy diet.
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