The technique is based on a specific protocol and observed reflexes that then uses chiropractic adjustive techniques on the sacrum. If you have never been "adjusted" before, an adjustment is the application of light force by hand or by an instrument in a very specific direction on the spine to help the body correct a subluxation of the spine. The technique itself should be very gentle with the pregnant woman. The beauty of it is that it is based on the fact that the baby wants to be, and is designed to be head down given the opportunity. The technique is designed to work with the body to normalize the bony and soft tissue structures of the pelvis so the baby CAN go head down. It is non-invasive and does not involve physically manipulating the baby at all.
In regards to the procedure causing early labor it cannot cause the body to do something other than what it is "programmed" to do... Meaning, when the baby turns, if the body is ready to go into labor you will go into labor. However, the head pushing on the cervix as it "drops" helps stimulate labor when labor is ready. Many times we do not see the patient until late into pregnancy so that possibility of labor starting AFTER the baby turns does exist. Chiropractic in general is designed to allow the body to work the very best possible without interference from subluxations. We free up the ability for the body to do exactly what it needs to do.
We have had babies turn in the office that the medical doctor had said did not have enough amniotic fluid to turn even it if wanted to. When they went in for their scheduled c-section the baby had turned. We have also seen patients scheduled for an external version that the baby turned the day of the scheduled version. This technique is amazing! It is best to have a few weeks to work with but we have seen them turn in as few as two visits in three days (or take as long as three weeks or longer with seeing the mother 3 and 4 times a week). Don't think it is too late. Just get started as soon as possible. You have nothing to lose and a natural birth to gain!!
Dr. Webster developed it over many years and had used it before his death in 1997 over 800 times (to his recollection) only about 25 that did not turn. Those that did not turn were later found to have an underlying reason anatomically or otherwise why they did not turn. He reported no adverse effects in any of these from the technique. Most other chiropractors that use it regularly note a 80-90% success rate. We have seen dozens of patient in our office with this approximate success rate as well.