A Glasgow study found smoking rates amongst mothers fell from 25.4% to 18.8% after the ban started on March 26, 2006.
The number of pre-term deliveries before 37 weeks also fell.
Scientists looked at pre-term delivery rates and gestational age in 716,941 single-baby births before and after the introduction of the smoking legislation.
There was also a 5% drop in the number of infants born small for gestational size, and an 8% decrease in the number born very small for gestational size.
The reductions occurred in mothers who smoked and those who had never smoked.
The researchers looked at data for babies born between January 1996 and December 2009 from Scottish maternity hospitals.
Professor Jill Pell, of the Institute of Health & Wellbeing at Glasgow University, led the research.
She said: "The potential for tobacco control legislation to have a positive effect on health is becoming increasingly clear.
"These findings add to the growing evidence of the wide-ranging health benefits of smoke-free legislation and support the adoption of such legislation in other countries which have yet to implement smoking bans.
"Irrespective of legislation, many women quit smoking when pregnant because of concerns about their infant's health.
"There has also been increased awareness of the need to protect children from exposure to tobacco smoke.
"While survival rates for pre-term deliveries have improved over the years, infants are still at risk of developing long-term health problems.
"So any intervention that can reduce the risk of pre-term delivery has the potential to produce important public health benefits."