One in every 1,100 pregnant women in the UK is extremely obese, a nationwide study by Oxford University researchers has shown.
The researchers found that extremely obese women with a body mass index (BMI) of 50 or higher experience greatly increased risks of complications during pregnancy and that basic equipment for their care was not universally available. With a rising birth rate and levels of obesity increasing, the findings published in the journal Obstetrics and Gynecology hold implications for maternity services in the UK.
Body mass index is a measure commonly used to classify adults as being underweight, overweight or obese. A BMI of 50 corresponds to a woman of average height (5ft 5) weighing around 22 stone (140 kg).
‘Extremely obese women are at risk of a wide range of problems in pregnancy, affecting both them and their babies,’ says Marian Knight of the National Perinatal Epidemiology Unit at Oxford University, who led the study.
‘There is a need to help people manage their weight before becoming pregnant and to make sure the appropriate services are in place to improve outcomes of pregnancy and childbirth for these women.’
Obesity is known to hold greater risks for mother and baby in pregnancy than in women of normal weight, yet there are no national data for the UK on the prevalence of obesity in pregnant women nor have there been any studies to address the risks among women who are extremely obese. Because of the small number of women who have BMIs of 50 or more, studies monitoring huge numbers of pregnancies are required to investigate the risks involved.
Researchers at the National Perinatal Epidemiology Unit have used data from the UK Obstetric Surveillance System – a nationwide reporting system that covers all births in hospitals in the UK – to measure the prevalence of extreme obesity among pregnant women in the UK and identify any increased risks of poor outcomes for mother and baby.
The study found there were 665 extremely obese women among an estimated 764,387 maternities in the UK between September 2007 and August 2008. That is a prevalence of almost one in every 1,100 maternities.
The outcomes of these pregnancies were compared to a group of 634 women with BMIs under 50 who gave birth in the same hospitals immediately before the extremely obese women.
Extremely obese women were more than five times more likely to have high blood pressure in pregnancy than pregnant women who are not extremely obese, nearly nine times more likely to have newly-diagnosed diabetes during pregnancy, and almost four times more likely to be admitted to an intensive care unit. Their babies are also more likely to be born prematurely.
Nearly half of extremely obese women have a caesarean delivery and a high proportion have problems with epidural or other anaesthesia for pain relief or for their delivery.
There is an effect on maternity and health services as a result. Extremely obese pregnant women received care from a wider range of health professionals, had more complex pregnancies, received more interventions and were more likely to give birth to preterm and high birth weight children – both groups that are susceptible to long-term health problems.
Basic equipment for the appropriate and safe care of obese women was not available everywhere, but no adverse outcomes for the mothers or staff were reported.
The study found that operating theatre tables and normal beds with a sufficiently high weight capacity were available for 80% of extremely obese women. But chairs of an appropriate capacity were only available as standard equipment for 30% of women, and hoists to allow safe lifting of women when they are incapacitated were only available for 20%.
‘We did not find any incidences where women were harmed by the lack of equipment. However, adverse outcomes for women and also for staff are likely to result if equipment provision remains inadequate,’ says Dr Knight.
‘In the context of an increasing birth rate and rising levels of obesity and particularly extreme obesity, this is an important area for maternity services to address.’