It helped my sister go into labour but she was full term I've been having terrible back pain and discomfort the past few weeks and asked my doctor could i use one and she advised me not to until at least 36 weeks I'm currently 34 weeks
I've recently started to use one. I'm only 23+4 but Ive been having horrendous back pain and this helps. At the moment I mainly use it for sitting upright as it encourages better posture and my soft sofa is getting more difficult to get up from and not to mention uncomfortable. I also use it for bits of gentle exercise by sitting on it and rotating my hips or leaning over it and rocking slightly. I can't comment on success with babies position though as I never used one with my first. However he was born in posterior position and so far this baby is also back to back so I intend to keep up with forward leaning positions in the hope he will turn the preferred way :)