Cost of hiring a weekly housekeeper?

Husband has OCD and with both of us working full time AND me being 7 months pregnant AND having a two year old, the house can get a little untidy and I could use some help. 
I pay the sitter to come here daily and I don't expect her to clean the house while she watches my son. 
So what's a fair price for a once or twice a week visit from a housekeeper?