Women who put on too much weight during pregnancy put their children at risk of type two diabetes, research suggests.
Many women still believe the myth that they need to ‘eat for two’, with nearly half putting on too much weight during the nine months of their pregnancy.
Now scientists have shown this has a marked impact on their children’s health by the age of seven.
Research among 900 women showed that those who put on too much weight in pregnancy were more likely to have children who developed insulin resistance - a key precursor to type two diabetes.
By the age of seven the children were also more likely to be overweight and have high blood pressure, putting them at risk of heart disease and strokes in later life.
The findings, published in the Diabetologia medical journal, are of particular relevance to Britain, where one in five women are obese at the start of their pregnancy.
But women in the UK are usually only weighed at the beginning of their pregnancy - which means they have no idea whether they are putting on too much weight in the months before they give birth.
The new research, carried out by the Chinese University of Hong Kong, suggests the answer is not simple dieting - because putting on too little weight during pregnancy comes with its own risks.
Women who did not put on enough weight had children with high blood pressure and poor blood sugar control at seven years of age.
The authors wrote: ‘We found evidence of linkage between gestational weight gain and several cardiometabolic risk factors in the offspring aged seven years, independently of maternal body mass index prior to pregnancy and glucose level during pregnancy.
‘These findings have important implications for both prevention and treatment.
‘There is a need for greater awareness and monitoring of weight gain during pregnancy.’
The Institute of Medicine in the US recommends mothers of a healthy weight put on no more than 2st 7lb during pregnancy, and no less than 1st 11lb.
Mothers who are overweight to begin with, with a body mass index of 25 to 30, should put on no more than 1st 10lbs, and no less than 1st 1lb.
And women who are obese, with a BMI of more than 30, should gain no more than 1st 6lb, and no less than 11lb.
Previous research of 1.3million pregnancies around the world found that 47 per cent of women put on too much weight during pregnancy, 23 per cent put on too little weight, and only 30 per cent meet the guidance.
The new findings come after doctors last month reported a surge in cases of type two amongst children as young as eight.
A national audit by the Royal College of Paediatrics and Child Health found the numbers of under 25s being treated for the condition has increased by 40 per cent in three years.
Just twenty years ago the condition was unheard of among children.
Mandy Forrester, head of quality and standards at the Royal College of Midwives, said: ‘During pregnancy women are very receptive to messages and advice about weight management issues and midwives can have a real impact on improving women’s health and wellbeing.
‘This research highlights the need for guidelines on weight gain in pregnancy in the UK.
‘Without this midwives have to use their own initiative and refer to American guidance.
‘There is a clear need for midwives to have the tools, guidance and training they need so that they can offer women the best possible support and care.
‘This is especially pressing because of the potentially serious complications that can arise in pregnancy as a result of women being overweight or obese. It is a real concern that some midwives do not have access to that most basic piece of equipment, scales.
‘We are calling for clear guidance on healthy weight management in pregnancy and will be looking at how we can take this forward so that women and midwives have the information, support and resources needed.’