Okay, you really have to be a die-hard junkie to appreciate these two videos, but I found them to be very educational. Two maneuvers are known to help with shoulder dystocia, the difficult situation in which the baby's head has emerged yet the shoulder remains caught behind mom's pubic bone. One technique is the Gaskin maneuver, where mom turns over onto her hands and knees, named for the midwife of midwives, Ina May Gaskin. The other is the McRoberts maneuver, where the mother is supine, and her legs are flexed all the way back - think knees to ears, opening the pelvis as much as is possible on one's back.
Here's a 3D animation of this - it's REALLY short, blink and you'll miss it, but it shows exactly how this action works on mom's pelvis and the baby's shoulder.
With that in mind, watch this longer, real-life situation.
It seems clear to me that the change of position is the key thing here; in the video above, mom had already been on hands and knees, so the Gaskin maneuver is, well, moot. So McRoberts was perfect. On the other hand, if mom was in anything like lithotomy, switching to hands and knees a la Ina May could really do the trick.
The threat of cephalopelvic disproportion and thus risk of shoulder dystocia is a common scare tactic used to frighten women into unnecesareans. Whichever maneuver ends up being the appropriate one, what I love about the second video here is how clearly it demonstrates that, with a skilled care provider who is armed with the knowledge of these options, shoulder dystocia, while something to take very seriously and address swiftly, CAN be coped with. The midwife worked efficiently and confidently, and there was no sense of panic or dire emergency. I can't help but wonder how this would have turned out in a hospital setting.