It's not recommended that you diet while pregnant but just a word of advice, you don't need to eat for two these days lol. Make sure you get all the nutrients you need but don't go mad with food or you'll have loads to lose again afterwards.
You must come off the plan as you are only just getting the minimum daily requirements for yourself.......so no.
You can do weight watchers or slimming world though as long as you tell your class leader.
But lipotrim is a definate no-no.....sorry