Obesity among pregnant women has reached epidemic levels, according to health experts, who are warning women not to "eat for two".
About half of women of childbearing age in England are either overweight or obese and about 16 percent of women are obese at the start of pregnancy, according to the National Institute for Health and Clinical Excellence (NICE).
Obesity during pregnancy increases the risk of serious complications like pre-eclampsia or gestational diabetes and the likelihood of miscarriage or stillbirth.
New guidance published by NICE on Wednesday encourages women to achieve a healthy weight before conceiving and says there is no need to "eat for two" when pregnant.
It offers tips on diet and exercise to help women manage their weight before, during and after pregnancy.
King?s College London?s head of maternal and foetal research, Lucilla Poston, who developed the guidance, said there was a "very worrying" prevalence of obesity in the UK.
?These guidelines are incredibly timely," she said. "We have an epidemic of obesity amongst our pregnant population.
?At St Thomas? recently we looked at our stats and there has been an exponential increase in obesity amongst our women attending ante-natal clinics, such that now 40 percent of the women are overweight or obese."
A woman is considered overweight if she has a body mass index (BMI) of 25?29.9 kg/m², or obese if she has a BMI of 30 kg/m² or more.
Women with a BMI of more than 30 should be encouraged to lose weight before they become pregnant, the health watchdog has advised.
But it also warned women not to try to lose weight while pregnant as it could harm the unborn baby.
Professor Mike Kelly, director of the Centre for Public Health Excellence at NICE, said: "About half of women of childbearing age are either overweight or obese and although obese women can have healthy babies, the evidence does suggest that there are more risks associated with pregnancies in women who have a BMI of over 30 when they become pregnant."
He warned against crash diets after pregnancy, instead recommending gradual weight loss to make sure the pounds stay off.
"Women should understand that weight loss after birth takes time, and physical activity and gradual weight loss will not affect their ability to breastfeed," Professor Kelly added.
NICE is urging health professionals to use the guidance to better inform women.
Local authorities should be offering physical and recreational activities for women with babies and children, at affordable prices and suitable times, the health body added.
Louise Silverton, of the Royal College of Midwives, said midwives were dealing with an increasing number of "complex births" as a result of rising obesity.
"These women need to see a midwife as early as possible in their pregnancy," she said. "They need more time to spend with a midwife to help and advise them."
The National Childbirth Trust (NCT) said women too often receive conflicting messages when it comes to weight loss.
NCT chief executive Belinda Phipps said: "There's a lot of conflicting advice about exercise, how much to gain during pregnancy and how to lose weight afterwards which can set a worrying example by encouraging new mums to embark on drastic weight loss programmes, which are not only unrealistic, but can also be very unhealthy."
Copyright 2010 AFP European Edition
