Which of the following sentences is/are grammatically correct?
Of the correct ones: what is the difference in meaning?
Are there other (more correct or more precise) ways to express the same meaning?

1. Being 19 weeks outside the womb my baby has learned to grab things.
2. Having been 19 weeks outside the womb my baby has learned to grab things.
3. Having been being 19 weeks outside the womb my baby has learned to grab things.