There are many benefits to having chiropractic treatment during pregnancy, for both mother and baby.
The earlier in the pregnancy treatment can commence the better, especially if back pain has been previously experienced. As the tissues loosen around the joints due to lactin hormone release, the joints have less support and move more, which is a common source of pain for mothers. This can affect not only the lower back, but also lead to pain further up the back, neck and shoulders due to changes in posture and centre of gravity.
Chiropractors can help with pregnancy-related pain by mobilising the joints that aren't moving enough, and by massaging and stretching muscles that are tight. Everyone's case is a little bit different so treatment varies depending on what the patient needs, and more importantly what is comfortable for them.
There is no evidence to suggest manual therapy is contraindicated in pregnancy, and in fact there is good evidence to support its role in both pre and post-natal care of PPGP. In combination with exercise, function can be improved and even reduce back pain during the birthing process.
Feel free to visit my advice blog for more details and self help advice with regards to pregnancy-related pelvic gridle pain (PPGP formally SPD):
http://www.thewhitchurchclinic.co.uk/2013/04/13/spd-symphysis-pubis-dysfunction/
The American Chiropractic Association also gives some great advice:
http://www.acatoday.org/content_css.cfm?CID=85