[R] how to combine several subsets?

[tooblue]

I simply put, 
> NEVER=subset(infants$bwt,ISNO1)
> UNTILPREGNANT=subset(infants$bwt, ISNO2)
> ONCENOTNOW=subset(infants$bwt, ISNO3)

and I wanna combine those three. 
I do it like 
ISNO=NEVER&UNTILPREGNANT&ONCENOTNOW

and R tells me 
1: In NEVER & UNTILPREGNANT :
  longer object length is not a multiple of shorter object length
2: In NEVER & UNTILPREGNANT & ONCENOTNOW :
  longer object length is not a multiple of shorter object length

I'm confused coz these are not objects, but a list of sets of numbers.
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