Background on the ‘obesity epidemic’
There has been a dramatic rise in the worldwide prevalence of obesity, leading to a World Health Organization (WHO) declaration that obesity is a major killer disease of the millennium on par with HIV and malnutrition. The rising prevalence of obesity has created a ‘global paradox’ in that the two extremes of malnutrition and obesity can coexist, at the same time, in the same country.1 Although there is a higher rate of men in the overweight category, globally more women are in the obese category. The epidemic of obesity is equally threatening the developing countries and the developed world.2
Definition of obesity
A common and universally acknowledged definition of obesity is: ‘a condition characterised by excess of body fat frequently resulting in a significant impairment of health and longevity’.The most frequently used criteria for measuring obesity is an elevated body mass index (BMI) of more than or equal to 30.3 Others include an increased waist circumference, an increased waist to hip ratio or a body weight of more than 90 kg. For this review, in accordance with the 1990 Institute of medicine (IOM) guidelines, an elevated BMI of more than or equal to 30 was chosen and this definition is widely acknowledged in the WHO surveys and The Health survey for England.
Normal weight gain in pregnancy
Recommendations for maternal weight gain in pregnancy were controversial during the 20th century. In 1990, the IOM recommended weight gain ranges for pregnant women depending on whether the pre-pregnancy weight was in the underweight, normal, overweight or obese ranges3 (Table 1). A systematic review in 2000 by the Californian School of Public Health showed that pregnancy weight gain within the IOMs ranges is associated with the best outcome for both mothers and infants.4
|Pre-pregnancy BMI||Recommended weight gain (kg)||Recommended weight gain (lb)|
|Obese, >29.9||At least 6.8 (higher limit not specified)||At least 15 (higher limit not specified)|
Worldwide prevalence of adult obesity
It is estimated that more than 300 million adults worldwide are obese, more than 1 billion are overweight and a further 115 million suffer related problems ranging from premature death to reduced overall quality of life.2 In the USA, approximately 64.5% of the total population is classified as either overweight or obese, with morbid obesity affecting more than 9 million adult Americans.5 The rising prevalence of obesity worldwide and in Europe are evident from the published figures at the International Obesity Task Force data base.6 Even more alarming is the rise of obesity among children worldwide, which is likely to have a significant effect on the future prevalence of adult obesity.1
Prevalence of obesity in UK
The prevalence of obesity in the UK in 2002 was estimated as 23% in women and 22% in men.7 The Health Survey for England 2004 revealed a steady rise in the prevalence of obesity in women from 16.4% in 1993 to 23.8% in 2004 and prevalence in men to increase from 13.2 to 23.6% between 1993 and 2004.8 This presents an enormous contemporary public health issue, with serious physical, psychological and social effects on the population. Despite this, healthcare provision for obesity is patchy.
Obesity is associated with more than 30 000 deaths every year as well as accounting for 18 million sick days and 40 000 lost years of working life. It costs the NHS half a billion pounds on direct costs and a further £2 billion to the wider economy. A House of Commons Report on Obesity estimated the economic cost of obesity to the country ‘conservatively’ at £3.3–£3.7 billion/year.9
Prevalence of maternal obesity in UK
Obesity in pregnancy carries significant maternal risk. This was highlighted in the last report of Confidential Enquiries into Maternal and Child Health (CEMACH) where obesity was identified as a risk factor for maternal death following the finding that 35% of all mothers who died were obese, representing a disproportionate number of deaths associated with obesity in childbearing women.10
In 2001, a retrospective study of 287 213 pregnant women in London found that 27.5% were overweight and 10.9% obese.11 A similar study of 30 167 pregnancies in Manchester found that of those where BMI was recorded, 18.5% were obese.12
These two studies, in conjunction with the CEMACH data, highlight how common the problem of obesity during pregnancy is in the UK. In fact, obesity is now the most common clinical risk factor encountered in obstetric practice. There is increasing concern that the rise in obese teenagers reaching childbearing age will exacerbate this problem.10
More than half a million women give birth annually in England and Wales.10 The BMI details of all these women are not known, but the ‘Maternal Obesity and Pregnancy outcome’ project, undertaken as a collaborative effort by the North East Public Health Observatory, The Food and Nutrition Group at the University of Teeside and The Regional Maternity Survey Office, is now collecting the relevant data for investigation into the relationship between obesity and outcomes of pregnancy.13 The increasing numbers of obese pregnant women and potential health and economic implications are staggering.