Birth weight of a baby can be increased by:
Cessation of smoking
Aspirin
Ca++  and vitamin D supplement
Bed rest
“Smoking is the single most preventable cause of IUGR in infants born in the united states—women who quit smoking at 7 months gestation have newborns with higher mean birthweights than do women who smoke throughout the pregnancy. Women who quit smoking before 16 weeks of gestation are not at any increased risk for an IUGR infant.”
COGDT 10/e, p 293
The answer is further supported by Williams 24/e, p 882
“In prevention of fetal growth restriction – smoking cessation is critical”
Williams 24/e, p 882