Gas and air pain relief at a major hospital could return within weeks, an NHS trust has said.
North West Anglia NHS Foundation Trust (NWAFT) stopped using Entonox at the Peterborough City Hospital maternity ward in February over safety concerns for staff.
Some mothers have told the BBC the suspension of this pain relieving gas mixture is "completely unacceptable".
NWAFT said "its reintroduction is a high priority for us".
Entonox is a mixture of nitrous oxide combined with oxygen.
The trust said its use was paused in February after the levels of nitrous oxide in the air were found to be above an acceptable level.
Melissa Davies, director of midwifery at the trust, said: "There were failed attempts to improve ventilation to bring nitrous oxide levels in balance at the hospital, after which scavenger units were ordered.
"These are specialist medical devices used to gather gas or aerosolized medication from the air."
The devices are expected to reduce circulating levels of the mixture by 80% and a Peterborough City Council health meeting - held earlier this week - tested the efficiency of the devices.
Ms Davies said: "If initial results suggest they can bring Entonox levels to an acceptable level it will then be a quick process to reintroduce it to the maternity ward."
During the time the pain relief has been unavailable, expectant mothers have been offered the pain relief drug Penthrox or otherwise changed their birth plans, such as by being rerouted to Hinchingbrook Hospital or being supported to have home births.
Ms Davies said bringing back Entonox in Peterborough has been "a long time coming" and that its reintroduction was a "very high priority".