Obesity in pregnancy can harm unborn child
The study revealed that 9,500 babies born to obese mothers every year are more likely to die or experience long-term issues with their health, compared to infants whose mothers weight is within the healthy range.
Jacqui Clinton, health campaigns director at Tommy's, said: "Poor diet, obesity, lack of physical activity, smoking and mental health problems can all impact on the healthy development of the baby."
Ms Clinton conceded that the charity is aware that it can be hard for mothers-to-be to change unhealthy eating habits.
Women only need to consume an additional 200 calories per day in the last 12 weeks of their pregnancy in order to remain healthy, the charity stated.
The NHS suggests that pregnant women who get hungry should aim to have healthy snacks and avoid fat-filled things such as biscuits, chocolate and crisps.