Wednesday, October 13, 1999 Published at 00:26 GMT 01:26 UK
Caesareans 'more likely for obese women'
Slimmer women are more likely to have a vaginal delivery
The more obese a pregnant woman is at the time of delivery, the more likely it is she will undergo a Caesarean section, researchers have found.
Dr Elizabeth Bell, an obstetric anaesthesiologist at Duke University Medical Center in the US, reviewed the medical records of 2,493 mothers who gave birth at Duke University Hospital.
She found that 833 - or one third - received a Caesarean section.
The body mass index (BMI) - the most reliable measure of obesity - of women who had a Caesarean section was almost twice that of women who delivered in the conventional way.
And that the more obese a patient was at time of delivery the more likely she was to have a Caesarean section, Dr Bell found.
Mr Andrew Bond, a consultant obstetrician and gynaecologist from Princess Margaret Hospital, Swindon, said he was not surprised by the findings.
Mr Bond said: "Obese women are more likely to get high blood pressure and therefore there is more likely to be some sort of intervention in late pregnancy.
"There is also quite a lot of evidence that some of these women are mildly diabetic and therefore likely to grow bigger babies that will not fit comfortably through the birth canal."
Duke obstetric anaesthesiologists are recommending that all obese women in labour are offered an epidural to avoid the potential health risks of general anaesthesia if a Caesarean section becomes necessary.
In the UK about 80% of women undergoing Caesarean section are given some form of local anaesthesia.
An epidural involves the placement of a thin catheter into the epidural space near the spinal column, which allows physicians to introduce anaesthetic agents that numb feeling in the lower half of the body.
It carries less risk to the health of the mother and child than general anaesthesia, which doctors find particularly problematic to administer to obese women.
When administering general anaesthesia, physicians insert a tube through the voice box into the windpipe to maintain an open breathing passage for the patient while she is unconscious.
All pregnant women retain fluid which makes them swell and prone to bleeding, but the effect is amplified in larger women, so it can be difficult to place the tube in the right place.
If it then turns out that physicians are unable to place the tube, the patients remain under the influence of drugs administered to stop them gagging and are unable to take care of themselves until the drugs wear off. The timing is especially critical if the baby is in distress.
Dr Bell said: "Every minute that passes that the baby is not delivered can lead to potential health problems for the baby."
This is complicated by the fact that since the baby pushes the diaphragm upward as it grows, pregnant women are more prone to acid reflux from the stomach, which can come up the throat and down into the lungs. This effect is also amplified in the obese.
BMI is calculated by dividing body weight by the square of the height. In the general population, a BMI of 30 is considered obese and 35 is considered morbidly obese.