A lot of it seems to depend whose name is on the house. When you buy a house it can be in your name only, or in both your names (legal document).
If YOUR name is on it she has no claim to it.
If BOTH your names are on it then you could be in trouble as she can claim half of it, and could probably get the court to agree to her staying in the house (if she keeps the child) and you moving out.
So my first suggestion would be to not move in together at all if it is not going to work (it is MUCH harder to split up once you are living together). I got maried to my first wife even though I knew it would not work (just to stop her nagging me to marry her) and we had 10 years of misery.
My second suggestion is to ONLY put you name on the house if you have paid all the deposit, mortgage repayments etc. If her name is on the house she will have a claim on it.
Search the web for legal sites about "cohabiting"
Here is one
http://www.lawonthewe...mily_Law/Cohabitation