Opening Up of the Perineum
This is a birth in this room (watch video).
It is her first child. What you see in that image is the opening up of the perineum.
The perineum gets slack, that controlled dilation avoids the rupture of the tissues. If the person makes an effort, instead of relaxing, ruptures can occur. (ver Parto de Cócoras: 1975 a 1987 - Estatísticas e Levantamentos).
Nobody is doing anything; the baby is coming out by itself.
It turns and falls on its side? If the labor is long and the baby is born tired, with low blood sugar, it has to undergo a recovery period.
If it stays with its tummy up, its tongue may fall behind, and if it has poor reflexes, is may suffer form asphyxia. Lying down on its side, while still receiving oxygen from the mother, air passage is guaranteed.
Since the placenta is higher than the baby, the blood flows down to it. The baby can be handed to the mother, because the umbilical cord has valves that stop the blood from flowing back. The baby is born over a soft and warm water bag. The idea is of a water mattress that will maintain its body temperature.
The baby is born and doesn’t cry. It is not because it has any problems, but because it is well and safe.