Scotland's busiest maternity unit is beginning a four-month trial in which disposable nappies are being replaced by washable ones.
Campaigners say real nappies save money
The switch at the Simpson Maternity Pavilion in Edinburgh is being made for financial and environmental reasons.
The start of the Simpson experiment is coinciding with Real Nappy Week.
It will allow mothers to compare the two types of nappy.
Under the 16-week pilot, one postnatal ward at the Simpson will use real nappies and the other will use disposables.
Women will be allowed to choose which ward they stay in.
Yvonne Clarke, from the Simpson Centre for Reproductive Health, believes parents should look to the long term.
"It takes so long for disposable nappies to biodegrade and our landfill sites in Edinburgh are fast and furiously being filled up," she said.
The washable nappies being tried out are held in place by poppers or adhesive material.
The hospital said the soiled nappies will be cleaned to stringent NHS standards at the Western General Hospital laundry.
Campaigners are pointing out that three million disposables are thrown away in the UK every year.
Environmentalists said disposable nappies make up at least 4% of household waste.
Collette Healy from campaign group Nappy Days said parents assume real nappies are still like folding origami with pins.
"Very few realise that modern nappies are now velcro closing with elasticated legs that are just as convenient as many brands of disposables," she said.
In Edinburgh, city officials say tackling the issue is an important element in the council's waste strategy.
Edinburgh City Council spends £200,000 on disposing of nappies each year.
Scottish Green Party leader Robin Harper praised the scheme.
He said: "This is a brilliant example of a community enterprise which benefits its members, the wider community and the environment."