Children born to obese mothers are 35% more likely to die before they reach 55, a study has found.
They also have a 29% increased chance of being admitted to hospital for heart attacks, angina and stroke than those born to mothers of a normal weight.
Experts analysed data for 37,709 babies delivered between 1950 and 1976 in Scotland who were now aged 34 to 61. Their mother's weight was recorded during her first antenatal appointment in pregnancy.
The results showed that offspring were 35% more likely to have suffered an early death from any cause by the age of 55 if their mother had been obese in pregnancy (body mass index of 30 or over). This held true even after other factors were taken into account, including mother's age, socioeconomic status, sex of the child, birthweight and their current weight.
Writing online in the British Medical Journal (BMJ), the experts concluded: "Maternal obesity is associated with an increased risk of premature death in adult offspring. As one in five women in the United Kingdom is obese at antenatal booking, strategies to optimise weight before pregnancy are urgently required."
Among the 28,540 mothers, 21% (5,993) were overweight at their first antenatal appointment and 4% (1,141) were obese. Among the 37,709 children, there were 6,551 deaths from any cause, with the leading cause of death being heart disease (24% of deaths in men and 13% in women). This was followed by cancer (26% of deaths in men and 42% in women).
The experts, from the universities of Aberdeen and Edinburgh, said the results were a " major public health concern", especially seeing as only 4% of mothers in the study were obese, "far smaller than current levels in the US and UK".
Louise Silverton, director for midwifery at the Royal College of Midwives, said: "This research shows the importance of women starting their pregnancy at a normal weight.
"However, not all pregnancies are planned and midwives encourage mothers to manage their weight during pregnancy. For those who are overweight or obese, there is a need to avoid excess weight gain and for those of normal weight to maintain this status.
"In addition, after the birth midwives work hard to support women to lose their weight - over a reasonable time period - so that they are an ideal weight for the next pregnancy. Midwives do communicate to women the long-term health risks of obesity for mother and baby."