If there is moderate to severe meconium in the amniotic fluid, waterbirth is not recommended. Mild to moderate meconium is fairly normal. It has been seen that meconium washes off the face of the baby and even comes out of the nose and mouth while the baby is still under water. If the water is stained and birth is imminent, the woman can lift her pelvis out of the water to birth the infant. This is usually considered an obstetric or midwifery emergency by most.
Protocols require the mother who is anticipating a large baby to leave the water.
Now there are some that find it is easier to assist a shoulder dystocia in the water. It is believed that tight shoulders happen more often because of mom or caregiver trying to push before the baby fully rotates. Better to wait a few contractions and allow baby to rotate. Because position changes in water are so much easier than dry land, a quick switch to hands and knees or even standing up with one foot on the edge of the pool helps to maneuver baby out. The water can be draining from the pool at the same time.