The College of Midwives says the centralisation of birthing units is putting pressure on neonatal facilities.

Christchurch Hospital's acute neonatal unit operated at or above 100% occupancy rate for all of last year.

NZ Midwives Chief executive, Karen Guilliland says closing small birthing units is to blame.

"There is a continual downgrading of the primary birthing unit in favour of centralising which is sort of an economic model but it is certainly not a model for having a maternity service that works."

She says healthy women are giving birth in hospital, taking up beds needed by sick women and babies.

"Big acute admitting hospitals are for women and babies that are sick needing help and what we have is a big acute emergency hospital full of well and healthy women and babies."

Guilliland says those women should be giving birth in primary units or at home.