It's five years since the law was changed to allow women prisoners to keep their babies with them up to aged two, and Corrections Minister Judith Collins says it's paying off.
Until the law change, women prisoners were only able to keep their babies with them until they were nine months old.
Ms Collins has been visiting the mother and baby units at Christchurch, Arohata and Auckland women's prisons.
Since they opened, 77 mothers have been able to keep their babies until aged two.
"Irrespective of a mother's circumstances, these babies deserve a good start in life and to be with their mothers," she said on Monday.
"The units provide a non-threatening, safe haven... being able to form a strong bond with their baby over a two-year period also helps the mothers' rehabilitation."