Should New Mom's/Mom's of 2-5 year olds w Who knows what is best for a child better than a mother?
To answer the question directly however, yes I think mom's with kids in the age group of 2-5 can work if circumstances are favorable.
Newborns do require lots of time and extensive care, toddlers require lots of devoted time which help them to grow their social skills, and most importantly they all require loving and nurturing environment which can equally be provided by joint efforts of other family members and sometimes a child care facility. There are some fanatically career minded, some have careers that don't allow much flexibility, some are balance seekers and some prefer to stay home full time even after kids grow up. Some mothers have choice of working, some don't. Sometimes working outside home (all moms are working: some work at home, some work at home and outside too) brings sense of satisfaction of accomplishing a specific ambition which helps mothers to take care of kids more efficiently and more devotionally while at home. Sometimes stress at work could bring out the negative impact on kids as well.
Stealth Parenting is one tough job, and I have known quite a few mothers feeling guilty on their own for being professionals, so I wouldn't judge them. I respect the decision a mother takes in her life about her kid and her career; working part time or full time or not at all (which I think is equally a bigger challenge for a well qualified professional mother).