According to a recent research, overweight women in their first pregnancy face a high risk of premature birth, having an underweight baby or suffering pre-eclampsia, a condition which can be fatal.

Although obesity has been linked to many problems during pregnancy, researchers wanted to examine if the seriousness varied in the first and subsequent pregnancies.

Scientists at Kings College in London looked at pregnancy data from 385 first time obese mothers in Britain and the Netherlands. The researchers found that four out of 10 women or 39 % had to have a Caesarean section which researchers say is the highest ever reported in the world.

They reported that obese first time mothers were twice as likely to give birth to an underweight baby weighing less than 5lbs 8oz
(2.5kg) as compared to women who were not obese. These mothers were also a third more likely to have an overweight baby and the risk of premature birth was also twice the national average at 11.9%.

The study reported that the obese women were six times more likely than first time mothers of healthy weight to develop pre-eclampsia, a potentially deadly syndrome in which blood pressure becomes raised because of significant amounts of protein in the urine. The researchers also said these women stayed longer in hospital, 4.6 days compared to a national average of three days or fewer.

Lead researcher, Professor Lucilla Poston of Kings College Hospital and St Thomas's Hospital, said, "The large proportion of small babies was particularly unexpected as obesity is more often associated with the birth of overweight babies.

"The high number of cases of pre-eclampsia found in this group was very concerning as this is a serious pregnancy complication which, in extreme cases, can result in maternal and/or foetal death.

"We must now start to consider first-time pregnancy as an additional problem in obese pregnant women, who we know are already more likely than thinner women to have a complicated pregnancy."

Premature births and babies with a low birth weight are at risk of suffering brain damage, breathing difficulties, learning problems and are more susceptible to infection. Why obesity causes these problems is not known Poston said but said it could be that insulin resistance, when normal amounts of insulin can't completely breakdown sugar in the diet, may be the problem.

"Normal pregnancy induces a mild form of insulin resistance and we know that obese people become more insulin resistant and that promotes diabetes, pre-eclampsia and macrosomia or bigger babies."

Mervi Jokinen, from the Royal College of Midwives, said, "Obesity is an issue that is becoming increasingly prominent in maternity care and midwives are aware of the complexities and potential problems that obesity brings into pregnancy.

"We need to ensure that women get early access to a midwife so that she can get lifestyle and weight management advice as soon as possible, and that this continues throughout the pregnancy and after the birth of the baby."

The study, the findings of which were published in the American Journal of Obstetrics and Gynaecology, was carried out by Tommy's, the baby charity, the Wellcome Trust, and the National Institute for Health Research (NIHR) comprehensive Biomedical Research Centre at Guy's & St Thomas' NHS Foundation Trust in partnership with King's College London. (Harkiran contributed to this report)