Quote from mandyjk77
So I know it's an emergency if you have a shoulder dystocia and the longer the head is out the worse the consequences, but why? The baby is still attached to the placenta so it doesn't have to breath yet. I know there can be damage to the upper brachialplexas nerves
causing paralysis or a clavical fx but how is the o2 supply diminished?
Thanks for any light you can shed
Because the body is so low in the pelvis when the head is delivered, the cord is compressed or nearly completely compressed from that point forward and there is extra pressure around the neck and shoulders from the vagina and perineum which further restricts blood flow to the brain. So you can reasonably assume that oxygen transfer from the cord stops within the first 30 - 60 seconds after the head delivers. After that, asphyxiation begins. How well baby does depends on how well oxygenated they were to begin with (have they been having deep variables with pushing for an hour? Are they metabolizing anaerobically already? If so they have less reserve and therefore less time before damage to brain tissue occurs) and I'm sure other variable factors like maternal tissue and cord thickness etc.