The second period of labor

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Stages of Childbirth
Head birth
Umbilical newborn

The second period of labor (or the period of expulsion) begins with the disappearance of the cervix and ends with the birth of the child..

Factors that determine the course of II. times
  • uterine contractions, their intensity peaks;
  • Abdominal pressure – is caused reflexively by the pressure of the head on the presacral receptors (the same as the defecation reflex – if the intestine is not emptied with an enema, there is a risk of passing stool);
  • mutual differences pelvic planes and the specific topic of the pelvis;
  • concavity of the birth canal (see below for the shape of the fetal head).

Birth parameters in the head position:

  • penetrating circuit – suboccipitobregmatic;
  • leading point – small fontanelle;
  • hypomochlion - subocciput;
  • head configuration - dolichocephalic.

We can divide the birth of the head into five stages:

Initial flexion and entry into the entrance plane[edit | edit source]

When entering the plane of the pelvic entrance, the head initially flexes so that it lowers the occiput and the lowest point is the small fontanelle.
The head first enters through a small section and, after passing through the biparietal diameter, is fixed by its large section in this plane.
Header position – is in the transverse or I position. oblique (when standing normally) or II. oblique (in less common positions).

Header progression to width and height[edit | edit source]

The head enters the spacious width and then the isthmus where it meets the pelvic floor resistance.
At this moment, the mother begins to engage the abdominal press (reflexively), the mother feels the active involvement in the expulsion as a psychological relief, but it is quite exhausting for her physically, especially for a first-time mother.

Normal and Abnormal Head Internal Rotation[edit | edit source]

In the region of the strait (or between the strait and the exit) the head rotates internally.
The following rule applies to all positions of the fetal head - during normal rotation, the leading point rotates forward behind the clip, regardless of where it was previously located - for example, in dorsoposterior positions, the rotating small fontanelle describes an arc of up to 135°.
Duration – tends to be longer in dorsoposterior positions (there are also more disorders of the mechanism of the second stage of labor, such as abnormal rotation or a deep transverse position).
Abnormal rotation – on the contrary, the leading point rotates towards the coccyx.

Normal internal head rotation

Rotation of the head around the lower edge of the symphysis[edit | edit source]

After the internal rotation was completed, the head entered the pelvic outlet with a sagittal suture in a straight diameter.

The head rests with the occiput on the lower edge of the symphysis.

The concavity of the birth canal forces the head to lean back (but it is not a change in the deflection position), thereby first cutting the area of the small fontanel (head of the head), then the forehead, the forehead, the face and finally the chin. The point of contact that rests on the symphysis is described as the hypomochlion - it is usually located at one pole of the penetrating circumference of the head. Birth "after abnormal rotation" - the hypomochlium is the bregma, the baby is born facing the symphysis (the head must first be maximally flexed before the head is born at the back, but then it deflects sharply in the front when the areas around the bregma are released - but that's should be avoided as sudden deflection may cause intracranial haemorrhage!).

  • A wider biparietal diameter is born in the area of the perineum, so a larger injury to the perineum occurs more often.

External rotation[edit | edit source]

The head, which was born with an arrow seam in the direct diameter of the pelvic outlet, turns according to the position of its body.

This rotation is conditioned by the mechanism of the birth of the hangers.

Braces delivery mechanism[edit | edit source]

Even before the head exits the pelvic outlet, the branches enter the pelvic inlet.

  • At entry, the biacromial suture is usually in the opposite oblique diameter to where the sagittal suture of the head was.

The shoulder placed more in front becomes the leader, placed below.
The brachii progress through the neck to the isthmus, where after birth the head internally rotates so that the leading brachii twists forward beyond the lower edge of the symphysis.
In the east, the biacromial diameter (as well as the sagittal arrow of the head) is in a straight diameter.
We deliver the front arm approximately to the level of the attachment of the deltoid to the humerus.

  • There, the hypomochlion is formed, around which we flex laterally, and thus give birth through the perineum and the posterior shoulder.

Duration II. delivery time – 15–20 min for a primiparous mother, 5–10 min for a multiparous mother.




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