The birth of children and clinical depression are no longer being formally reported as incidents in Australian detention centres, while self-harm events have been downgraded from critical to major, according to new guidelines from the detention service provider Serco.

The new guidelines were created in March this year, when the previous Labor government was in office.

Incident reports are how Serco communicates with the immigration department about events in detention centres, such as births, deaths, assaults and escapes.

The new reporting guidelines, which were obtained under freedom of information laws by Refugee Rights Watch, significantly alter the categories of incidents Serco is required to report to the immigration department. While some categories have been replaced or expanded, “birth of a child” and “clinical depression” have been removed, with no apparent replacements.

The removal of the categories means it is unclear how the immigration department is now being informed about births in detention facilities. It also means that no performance audits in the form of “post incident reviews” would occur for childbirths.

Serco issued a statement saying the department determined how an incident was categorised.

"The categorisation of incidents, that is, whether an incident is classed as minor, major or critical, is determined by the department. The categories relate to reporting timeframes.

"We are required to report minor incidents within 24 hours, major incidents within one hour and critical incidents within 30 minutes."

The federal government has come under increasing pressure for its care of children and pregnant women in detention centres. An asylum seeker on Nauru who was transported to Brisbane hospital to give birth was separated from her newborn at night, while a number of unaccompanied minors on Nauru have been transferred back to Christmas Island due to concerns about their mental health. Earlier incident logs show there were 28 births in Australian detention centres between October 2009 and May 2011.

“It’s shocking to think that a birth behind bars doesn’t even rate a mention any more,” the Greens immigration spokeswoman, Sarah Hanson-Young, told Guardian Australia.

“This change in protocol is very concerning. Will the department of immigration now plead ignorance when it comes to the number of babies born in detention? This government’s addiction to secrecy is becoming ridiculous and dangerous.

“As a wealthy and generous nation Australia should be treating refugees with care but, instead, this government’s policies are creating the next generation of damaged children,” Hanson-Young said.

Among other changes to the guidelines are the downgrading of “self-harm – actual” and “assault – serious” from critical incidents to major incidents. This means Serco has more time to inform the department of when an incident has occurred. Bomb threats and unauthorised media presence have also been downgraded from critical to major.

Some categories have been expanded to give more detailed reports. Assaults are broken down further so that incidents involving children are logged separately, and voluntary hunger strikes have been reclassified as “food/fluid refusal”.

Sexual assault has been listed as a separate category. Guardian Australia had previously had to lodge freedom of information requests with Comcare to reveal the number of sexual assaults in detention centres, because the immigration department did not log this information as a separate category.

Guardian Australia contacted the immigration department and the minister for immigration and border protection, Scott Morrison, to see whether the immigration department had any involvement in the incident categories, but they declined to respond.