step mom's.. need some advice

So for about the past 3 months my SO has been begging for us to start ttc. we had talked about kids years ago when we first got together and we both wanted one, but it being a new relationship of course wanted to wait and then after 3 years of being together we though it would be best to wait and have custody settled first. Well that's been done for about 2 years now and he is wanting to start. I am too but I'm unsure about how my step daughter will react to this. she is going to be 8 soon and has been an only child with us and is very attached to me. I'm more afraid that she might have a hard time with this. how did your step child/ren react when you found out you were pregnant? I do so much with her and I'm afraid that being pregnant and all the changes I won't be able to do all that I have been for so long and that may have some impact on her.