I have never dealt with a pregnant cat either. but have you considered taking her to your vet. She/he could probably give you that answer and provide any health care, including disease checks for her to help keep her & her kittens as healthy and safe as possible.
My cat is approximately 7-8 yrs. old. he has asthma & IBS/chronic pancreatitis. AS a result he is on prednisolone twice a day. he had to have his belly shaved last summer for an ultrasound & his hair has never grown back. Does anyone know if that could be due to long-term steroids?