More than 10,000 who had babies in the 12 months to the end of March 2013 were obese, representing 18.1 per cent of all new mothers.
Mothers with the condition were more likely to be from deprived areas, older and at higher risk of requiring an emergency caesarean, according to the report from ISD Scotland.
In the study which measured body mass for the first time, overweight mothers accounted for 23.8 per cent of the 55,542 deliveries in 2012/13, equivalent to more than 13,000 women. The figures mean that overweight and obese women accounted for slightly more births in Scotland than women who were a healthy weight - 41.7 per cent of the total.
A BMI of 25 to 30 is classed as overweight and 30 to 35 is obese. However, only mothers whose BMI exceeds 35 - "morbidly obese" - are considered abnormal by the health service and taken out of the normal clinical pathway for specific help and support.
Gillian Smith, director of the Royal College of Midwives Scotland, said: "We are in the grip of an obesity epidemic. Some of the knock-on effects for pregnant women include the impact on their mobility, and the mode of delivery because we know they will have a higher caesarean section rate.
"They will also have a higher post-partem haemorrhage rate, they are at higher risk of suffering stillbirths if they are obese and we have to keep an eye on hypertension."
Ms Smith added that obese women were more likely to suffer from infertility, and said that more needed to be done to confront expectant mothers about their weight. Obesity can heighten the risk of miscarriage, gestational diabetes, pre-eclampsia, blood clots and having a baby with an abnormally high birthweight. She added: "The idea that you have to eat for two is a fallacy. Putting on a stone during pregnancy is too much."
A Scottish Government spokesman said: "An action plan was published in January 2011 to help NHS Boards, local authorities and others to improve the nutrition of pregnant women, babies and young children."