Babies are not a marriage saver.
First off id like to say, if you feel like you need to have a baby to save your marriage it probably wont work out in the first place. (That's my own 2 cents) Another person to take care of will only bring tension to the home and not enough time to work on the marriage problems that you already have. So here's some facts about having a baby that I hope will make you change your mind.
First babies require CONSTANT care. There wont be a lot of time for you and hubby anymore. Some men even feel a little jealous toward baby because mothers will put baby before anything and everybody.
Second you will not be getting any sleep so irritability will come into play. Third money issues will most likely arise do to the HIGH cost of having a baby.
And stress is a HUGE thing to think about. Less money, less sleep, less sex, less time for hubby and more diapers, puke, stress and I guarantee more arguments between you and your lover. Ask someone that has kids and they will tell you to think twice.