The Association of Ontario Midwives has filed a human rights complaint over what it says is the government's refusal to comply with pay equity for midwives.
It says midwives "suffer a gender penalty" because they are a female-dominated workforce.
Matthews says the government wants more midwives so women have another option when giving birth, but she can't understand why they'd ask to double their pay.
The health minister says she is "puzzled by their approach."
Matthews says midwives are well compensated in Ontario, which she says also pays about $33,000 in liability insurance for each midwife that other provinces don't cover.
Midwives spokeswoman Lisa Weston says the association was "forced to sue" after all its efforts to ensure pay equity were dismissed by the government.
"The most recent pay equity reports confirm the pay equity gap for midwives means we are only paid 52 per cent of what our work is worth," Weston said in a release.
The association said there are almost 700 registered midwives in Ontario, serving communities in 100 clinics across the province.