Cigarettes smoked per D^1st trimester:NRat:Pt:^Mother:Qn
cigarettes smoked per d^1st trimester:nrat:pt:^mother:qn
Cigarettes smoked per D^1st trimester:Number=Count/Time:To identify measures at a point in time:^Mother:Quantitative
cigarettes smoked per d^1st trimester:number=count/time:to identify measures at a point in time:^mother:quantitative