No I'm sorry, a pregnant mother residing in a shelter that was already on the list would not receive a priority for that reason in Sonoma County. Each County may set certain preference points for their waiting list and Sonoma only gives preference points to Veteran's, Current residents or persons working in the jurisdiction of Sonoma County HA, Persons with disabilities, seniors, and families with minor children, and the date and time the application is received.
So she may receive a preference point if she resides in that county and she would receive another one once her child was born. She would need to report her child's birth and provide a copy of the birth certificate and SS card in order to receive that preference.
It is also very important that if she is in a shelter that she provide the Housing Authority with a good mailing address. The Housing Authority will contact her by mail when she reaches the top of the waiting list and if the Housing Authority does not receive a response they will remove her from the list.
Since you mentioned Sonoma county you may also want to consider the Housing Authority of the City of Napa, City of Fairfield Housing Authority, City of Benicia Housing Authority, City of Vallejo Housing Authority, Suisun City Housing Authority, Contra Costa County Housing Authority, and Sacramento Housing Redevelopment Agency.
20 years working for the Section 8 program