Almost half of pregnant women in Scotland are either overweight or obese, new figures show.
Cancer Research UK has urged the Scottish Government to act after the "deeply concerning" statistics were revealed.
It urged a crackdown on supermarket multi-buy deals for junk food, arguing this would help everyone – including mothers-to-be – to cut back on foods with high levels of sugar, fat and salt.
Figures for 2017-18 showed 42% of women who gave birth were classed as being a healthy weight, while 26.2% were overweight and 22.7% were obese.
Three-fifths (61%) of pregnant women over the age of 40 were either overweight or obese, compared to 36% of those who were under 20.
"There has been a gradual increase in the proportion of overweight and obese women in all the age groups in the past five years," the report noted.
Professor Linda Bauld, Cancer Research UK's prevention expert, based at the University of Edinburgh, said: "It's deeply concerning that around half of women are overweight or obese in pregnancy."
She spoke out after new NHS figures for 2017-18 showed 13,427 mothers-to-be were recorded as being overweight when they had their initial booking in appointment for their pregnancy, with a further 11,604 classed as being obese.
Both of these totals were down on the previous year, when 50.7% of mothers to be were in these groups.
Prof Bauld said: "Carrying too much weight causes around 2,200 cases of cancer every year in Scotland.
"New laws would work hard to turn around Scotland's poor health record but also do a great deal to ensure the future of new generations is in much better shape."
She said: "Tackling obesity is complex but laws to restrict supermarket multi-buy offers on junk food would be an effective measure, helping everyone, including mums-to-be, from filling their shopping trolleys with foods high in fat and sugar."
The figures also showed another rise in the number of women having surgical births, with 15.7% of all babies delivered in 2017-18 born by planned Caesarean section.
A record number of 7,886 infants were born this way, compared to 3,051 in 1975-76.
There was a slight fall in the number of babies delivered by emergency Caesarean section, with this falling from 8,710 in 2017-17 to 8,460 in 2017-18.
But the falling birth rate meant the proportion of babies born this way rose from 16.7% to 16.8%.
NHS data revealed of the 51,197 hospital births in Scotland in 2017-18, 14.4% were to mothers who were smokers, down from 14.8% the previous year and 28.7% two decades ago.
More than half (54.2%) of women giving birth were aged 30 or above, with almost a third (32%) of women having a baby aged between 30 and 34, while 18.3% were between 35 and 39 and 3.9% were 40 or older.
This continues the trend of women leaving having babies until later in life, with 53.3% of mothers aged over 30 in 2016-17, compared to just 19.5% in 1975-76.
Health Secretary Jeanne Freeman said: "The downward trend over the past two decades of women not smoking during pregnancy is hugely encouraging and means a healthier start for both mum and baby.
"We want to help women be as healthy as possible in their individual circumstances.
"That's why it's crucial we support women to seek as healthy a weight as achievable, particularly prior to and in pregnancy.
"We are currently working on an action plan with NHS Health Scotland which will broaden the information and support available to all women of child bearing age across Scotland, as well as their partners.
"This will focus not only on healthy weight and diet but also mental and physical health, vitamin supplementation, tobacco and alcohol use before becoming pregnant.
"This is in addition to our ambitious Diet and Healthy Weight Delivery Plan, published in July, which sets out our aim to halve childhood obesity by 2030.
"It includes a wide range of proposals to help everyone eat well and have a healthy weight.
"To tackle our nation's damaging relationship with junk food we are also consulting on restricting the in-store promotion and marketing of food that is high in fat, sugar or salt but with little or no nutritional benefit."