My stray in heat

Question
I have recently taken in a cat - I took her in because I new she was in heat and want to prevent more kittens living on the street - obviously my home is all new to her and I'm starting to think I was to late and she is already pregnant - She didn't meow all night - she doesn't want my male cats around her - she gets extremely mad when I touch her hind quarters and starts growling at me (this shocks me because she was previously a very sweet cat) I don't know if she is in heat anymore though?!?! I have an appointment to get her fixed on Wed. but am unsure if she may already be pregnant in which case I don't really want to kill the kittens.

Answer
Hi Ashley,

I applaud your decision to get this kitty spayed to prevent more unwanted kittens and I agree, I wouldn't want to kill any unborn ones, either.  Its entirely possible that she is pregnant and you might want to wait on the spaying until you see more signs one way or the other.  She may have been as friendly as she was because she was in heat and now that she's not more of her true nature is coming out.  And, as you say, your house is new to her.  I assume your male cats are neutered and therefore could not impregnate her if she isn't already.  If they're not you could do that first and just wait on the spay for a while.  The gestation period for a cat is a little over two months and in that time she will either gain a lot of weight in her midsection (she'll probably gain some just being inside and eating right) or she'll go back into heat.  Then you can make a decision what to do.