This stage is much shorter than the first—generally lasting about an hour—and it is often gratifying to the mother, for at this point she can take an active role. When the cervix is fully dilated, the fetus has no further barrier in the upper birth canal, and the full power of the uterine contractions works to drive the baby downward along the lower birth canal. The contractions are now very intense and occur at about two-minute intervals and last for about one minute. During them, the woman feels an intense desire to bear down and expel the baby.
The instinct is appropriate; pushing with the abdominal muscles and diaphragm will speed the baby on its way. But the mother should await guidance, since pushing with these muscles is effective only if the uterus is in contraction at the same time. The baby turns a quarter way around, to present its head at the birth passage with the narrowest diameter foremost. Each contraction now brings the child closer to the exit. Head foremost, it will first emerge from the bony pelvis, the coccyx moving out of its way, and then through the lower vaginal tract. The perineum, the outer muscle wall of the passage, stretches to a fantastic degree.
If the delivery is to be a spontaneous one, the laboring woman may feel both the urge to retract in the face of the terrific force that seems ready to tear her apart, and at the same time a tremendous desire to expel the baby, to get it past this point and relieve herself of it. Now the vulva dilates to let the head through. The top of the head appears, and the vulva stretches to an oval and finally a circular openinge As it stretches, the physician
often chooses to make a small cut into the perineum with a scissors to widen the opening. He performs this episiotomy to prevent development of a natural tear, with ragged wound edges, and to avoid producing laxness in the vaginal tissues from overstretching.
The vulva stretches around the largest diameter of the baby’s head; this is called crowning. Then the forehead, nose and chin appear and the entire head is out—generally with the face downward. The obstetrician then gently turns the child and, with the final pushes of the mother, he brings out first one shoulder and then the
other. The rest of the baby’s body follows easily, for it is narrower and the baby is born.