Whanganui midwives are working to educate people about the dangers of wrapping babies in polar fleece blankets.
"We know polar fleece blankets are made from the likes of recycled bags and bottles," midwife Angela Adam said.
Mrs Adam, who is Whanganui's maternity community quality co-ordinator, said polar fleece blankets were made from plastic-based fibre which meant the materials did not breathe.
This meant babies could overheat or sweat, then get too cold because the sweat would not evaporate. Both of these could contribute to sudden, unexpected death in infancy.
"As midwives in the maternity unit, we don't support the use of polar fleece blankets," Mrs Adam said.