I must add my voice to those of your good friends here. And they are good friends, however harsh some of their words may seem to you now.
The current state of your relationship is NO PLACE to raise a child. And no, having a child does NOT guarantee that "she cannot leave." Not at all. She CAN leave, and there will also be a dependent child, and then what? Who gets the child? Who pays child support? Etc. S/he will be caught in the middle any time your wife decides to play "Leave PNG For A While And Then Come Back"?! That can be devastating to a child. Scotty is right. The relationship MUST be solid and healthy before adding a child to the mix. A child is not a fix-it for a dysfunctional relationship. A child would be victimized by this situation. I've known people who have had babies to try to keep a wandering partner from leaving. In all cases, years later, they've turned into divorced couples with a scared or angry child being tossed from guardian to guardian amidst an ongoing chaos of changing custody agreements, and/or only seeing a beloved parent once or twice a year throughout childhood and teen years.
Please PNG, if you do decide to enter Round 5 of this scenario with your wife who has already left and come back 4 times, please do not bring a child into the home unless you AND she have both had extensive couples' counseling with a professional. Please - for the sake of the child. The first part of being responsible for a child's well-being is knowing when you are not positioned to give the child what s/he needs most. A safe, consistent loving environment. How safe, consistent and loving has your relationship with your wife been, and do you really want a child to feel the way you do now, only at the age of 2 or so and be unable to articulate or contain such feelings the way an adult can?
And I agree with your other friends. Re-read your words on the thread you started when she left you the fourth time. Are you truly willing to sign up for that experience all over again? Yes, I believe in second chances. But four and five times?!! What would you think if someone else told you their spouse left them 4 times? Would you be confident your friend wouldn't be hurt a fifth time? The sheer number of times this has happened indicates an entrenched and ongoing pattern. It's been her proven track-record. Are you really sure you are okay with signing up for round five?
Never linger too long with the ignorant,
throw stones at their talk.
Walk only with the lovers,
the mirror of the soul gets rusty when
dipped in muddy water.