This is a really good question. When babies are not "head down" in the pelvis right before your due date, your provider has several choices to make. The provider can choose to deliver the baby as a breech (yes, that is still done by skilled doctors!), or plan a Cesarean delivery, or attempt to change the baby's position so a vaginal delivery can be accomplished.
Your provider has decided to try and change the baby's position from buttocks or feet down, to head down. This is called "external version." The doctor will actually move the baby with his or her hands, trying to roll the baby's head and shoulders forward and turn the baby around so the head is down and the buttocks are up in the top of the uterus. While this is being done, a nurse will probably be monitoring the baby's heartbeat, just to be sure everything is fine. External version has a good chance of success (the success rate is about 65 percent in the U.S.), depending on some factors. The shape of the woman's pelvis seems to make a difference, and how snugly the baby is fitting into the pelvis also makes a difference. Also, some doctors are more skilled than others in version.
Will it work? You have about a 65 percent chance that it will, but sometimes babies change back to the breech position after the version. There's no way to predict that. Will it hurt? Women I know who have had versions say it is not painful, but a bit uncomfortable, especially if the baby is large. The version itself should not harm your wife or your baby. Versions are considered safe when done by skilled doctors. Good luck!