Midwives at Waikato Hospital in Hamilton say the number of family members attending births is putting them and patients at risk.
They are in talks about possibly restricting the number of family members attending a birth.
Waikato District Health Board (DHB) associate director of midwifery Corli Roodt said having so many people in and around the delivery suite put added stress on mothers and was affecting the midwives' ability to work safely.
The board said sometimes as many as 15 relatives could be in a birthing room at one time, and it was putting staff and patients at risk.
Midwives had been threatened and abused, property had been stolen and equipment vandalised by people and extended family wandering around the lounge and hallways.
"We've had graffiti in a meeting room, we've had artwork being destroyed. We've had milk being poured into a fish tank and the fish dying of course," Ms Roodt said.
"Then we have people taking the wheelchairs to have a race about the corridors. One of the biggest concerns is unsupervised children. We've had babies being left asleep in prams in the waiting rooms with no adults around so staff need to go around looking for the parents.
"Our labour rooms aren't very large, so if there are many support people stacked into a room it becomes very cluttered and noisy, and women who labour need the space and the peace to do what she needs to do, so if there are support people talking on phones and chatting loudly it is disruptive."
A DHB spokesperson said one option was to restrict the number of supporters.
Other departments at Waikato Hospital, such as intensive care, limited visitors to two at a time.
At some other hospitals, restrictions are only put in place in the birthing room if there is an emergency during labour or a mother needs to go into a operating theatre.
Lakes District Health Board manager for women, child and family service Donna Mayes said attendance was limited when several doctors and clinicians were needed in the room.
"At Lakes DHB facilities, we allow two people rather than just one because the one person is likely to be the woman's partner or the infant's father and will probably find the situation very distressing without another family member or close friend to support them."
Capital and Coast DHB chief operating officer Chris Lowry said it had similar restrictions.
"There is no limit to the number of support people who can be in the delivery suite during a birth, so long as the numbers are such that staff are not impeded. If this occurs, staff would ask some support people to leave the room so as not to impede the care being provided to the patient.
"Should a birth occur in an operating theatre, only one support person is permitted. This is so as to not to impede staff in their care of the patient. This limit has always been in place."