Telling SD about a new baby - help!

[AmethystMoon]

My DP has two DD from his marriage and he's worrying about how to tell them if we have a baby together. They are lovely girls and understandably protective of their mum who they live with. They are 11 and 14 and on the perfectly nice to me ( I do realise I am lucky). DP separated from his wife 3 years ago (she has barely accepted that he's not coming back even after 3 years). We are planning to start trying for a baby in a few months time but he is really stressed that it will drive them away from him when they find out (if I even get pregnant - I have had no children yet but want one so much it hurts). The eldest has had counselling and seems to be getting on well with her dad but the youngest is quite insecure. She was always brought up as the 'baby' and seems to love that role. Their relationship with their dad is good and I know they enjoy seeing him as does he them. They come and stay with us from time to time and see him twice a week. I know they prefer to spend time alone just the three of them, which I totally understand and I do try to make sure they get time together as much as possible. I sometimes go out to see friends for a few hours if they're staying for the evening to give them time alone. Anyway I want to be able to make some helpful suggestions to my DP as to how he might broach this with them and I wondered if anyone could help?

you must tread very, very carefully.
one way to do it is to keep telling your stepdaughters how much you enjoy spending time with them, how much fun you have with them etc [but be sincere of course]
and then start dropping in comments like 'id love to have girls like you someday'
just so they know that you think about having kids of your own. i think its better if you gradually lead up to it, rather than dropping a bombshell one day.
then if you do get pregnant[and god luck by the way!] id get DH to tell them, but dont take them out somewhere on their own and turn it into a massive deal, like they SHOULS have a problem with it. get him to talk to them at home, encourage them to ask questions, i wouldnt come out with stuff like 'it doesnt mean we wont love you any less' unless they say something along those lines, because that thought might not have entered into their heads! make the baby all about THEM getting a new sister, and involve them as much as possible, but dont baby talk all the time.