Baby cries so hard during sleep training she stops breathing for a second

eaprice01

We just started the ferber method with my 4 month old and while she has fallen asleep right away with dad with minimal fussing,  she literally screams bloody murder with me. Today I noticed on the monitor she kept on falling asleep then startling herself to wake and when I went in to check on her I realized she was waking up because she had stopped breathing for a second!!


Any advice?? Yes we're setting time limits and yes I'm going in to comfort her periodically.  Also I asked my mom (a veteran mom of 8) and she said she's fine,  it's normal for babies to do that when they're that upset and I should have left her in there and let her learn to comfort herself.  

Also, I'm only interested in CIO or sleep training advice. If you're anti CIO our opinions differ so please don't comment.