The association says more than 6,500 e-postcards have been sent to Premier Dalton McGuinty advocating for birth centres.
It says hundreds of supporters are also using Facebook to promote the benefits of birth centres and funding for the pilot project in the 2012 budget.
Ontario's 550 registered midwives currently attend births in hospitals and women's homes.
The association says birthing centres could cut costs such as medical and surgical expenses.
And it says reducing Ontario's rate of caesarean section to 15 per cent could save $50 million a year.
"Establishing free-standing, midwifery-led birth centres would cut health care costs by giving women with healthy pregnancy and birth another option for community-based care," said Katrina Kilroy, president of the association.
The association adds that women who deliver in birth centres may have a lower risk of serious infections, particularly hospital-based infections with antibiotic-resistant bacteria.