Childbirth (Пологи)

Childbirth (also called labour, birth, partus or parturition) is the
culmination of a HYPERLINK «» \o
«Human» human HYPERLINK «» \o
«Pregnancy» pregnancy or HYPERLINK
«» \o «Gestation» gestation
period with the delivery of one or more newborn HYPERLINK
«» \o «Infant» infants from a
HYPERLINK «» \o «Woman» woman ‘s
HYPERLINK «» \o «Uterus» uterus .
The process of human childbirth is categorized in 3 stages of labour.
The first stage accomplishes the shortening and then the dilation of the
cervix. It is deemed to have started when the cervix is 3 cm dilated,
and ends with full dilation. Contractions begin in the first stage of
labour although they may be irregular and sporadic at first. The second
stage, often called the pushing stage, starts when the cervix is fully
dilated and ends with the expulsion of the fetus. In the third stage,
the HYPERLINK «» \o «Placenta»
placenta detaches from the uterine wall and is expelled through the
birth canal. HYPERLINK «» \l «cite_note-0»
\o «» [1] Preceding the onset of labour is a period called the latent
phase. This phase may last many days, and the contractions are an
intensification of the HYPERLINK
«» \o «Braxton
Hicks contractions» Braxton Hicks contractions that start around 26
weeks gestation. Latent phase ends with the onset of active first stage

The mechanics of birth

Because humans are bipedal with an erect stance and humans have
relatively the biggest head and shoulders to the size of the pelvis of
any species, humans fetuses are adapted to make birth possible.

The erect posture causes the weight of the abdominal contents to thrust
on the pelvic floor, a complex structure which must not only support
this weight but allow three channels to pass through it: the urethra,
the vagina and the rectum. The relatively large head and shoulders
require a specific sequence of manoeuvres to occur for the bony head and
shoulders to pass through the bony ring of the pelvis. If these
manoeuvres fail, the progress of labour is arrested. All changes in the
soft tissues of the cervix and the birth canal are entirely dependent on
the successful completion of these six maneuvers:

Engagement of the fetal head in the transverse position. The baby is
looking across the pelvis at one or other of the mother’s hips.

Descent and HYPERLINK «» \o
«Flexion» flexion of the fetal head

Internal rotation. The fetal head rotates 90 degrees to the HYPERLINK
&redlink=1» \o «Occipito-anterior (page does not exist)»
occipito-anterior so that the baby’s face is towards the mother’s

Delivery by extension. The fetal head passes out of the birth canal. Its
head is tilted backwards so that its forehead leads the way through the

Restitution. The fetal head turns through 45 degrees to restore its
normal relationship with the shoulders, which are still at an angle.

External rotation. The shoulders repeat the corkscrew movements of the
head, which can be seen in the final movements of the fetal head.

These movements are all due to the relationship of the bony head and
shoulders of the fetus to the bony ring of the mother’s pelvis and are
independent of any changes in the maternal soft tissues.

The stages of normal human birth

Latent phase

The latent phase of labour causes confusion with many. Latent phase may
last many days and the contractions are an intensification of the
«Braxton Hicks contractions» Braxton-Hicks contractions that start
around 26 weeks gestation. HYPERLINK
«» \o «Cervical
effacement» Cervical effacement occurs during the closing weeks of
pregnancy and is usually complete or near complete, by the end of latent
phase. Cervical effacement is the incorporation of the cervix to form
the lower segment of the uterus. The muscular portion of the uterus is
the upper segment, and is made of HYPERLINK
it&redlink=1» \o «Non-striated muscle (page does not exist)»
non-striated muscle . The lower segment of the uterus has no muscles and
is comprised of the cervix itself, which becomes massively stretched and
thinned out. This cervical effacement will usually be accomplished fully
prior to the onset of labour. The degree of HYPERLINK
«» \o «Cervical
effacement» cervical effacement may be felt during a vaginal
examination. A ‘long’ cervix implies that not much has been taken into
the lower segment, and vice versa for a ‘short’ cervix. Latent phase
ends with the onset of active first stage; when the cervix is about 3 cm

Mother and newborn with HYPERLINK
«» \o «Umbilical cord»
umbilical cord still attached after a HYPERLINK
«» \o «Water birth» water birth

First stage: contractions

The first stage of labor is an active stage and should not be confused
with the latent phase of labor.

The first stage of labor starts classically when the effaced cervix is 3
cm dilated. There is variation in this point as some patients may
present a little before this point with active contraction, or later,
without regular contractions. The onset of actual labor is defined when
the cervix begins to progressively dilate. Rupture of the membranes, or
a blood stained ‘show’ may or may not occur at around this stage.

Uterine muscles form opposing spirals from the top of the upper segment
of the uterus to its junction with the lower segment. During effacement,
the cervix becomes incorporated into the lower segment. During a
contraction, these muscles contract causing shortening of the upper
segment and drawing upwards of the lower segment, in a gradual expulsive
motion. This draws the HYPERLINK «»
\o «Cervix» cervix up over the baby’s head. Full dilatation is reached
when the cervix is the size of the baby’s head; at around 10 cm dilation
for a term baby.

The duration of labour varies widely, but active phase averages some 8
hours for women giving birth to their first child («primiparae») and 4
hours for women who have already given birth («multiparae»). HYPERLINK
«» \l «cite_note-1» \o «» [2]

Second stage: delivery

This stage begins when the cervix is fully dilated, and ends when the
baby is finally delivered. At the beginning of the normal second stage,
the head is fully engaged in the pelvis; the widest diameter of the head
has successfully passed through the pelvic brim. Ideally it has
successfully also passed below the interspinous diameter. This is the
narrowest part of the pelvis. If these have been accomplished, all that
will remain is for the fetal head to pass below the pubic arch and out
through the introitus. This is assisted by the additional maternal
efforts of «bearing down». The fetal head is seen to ‘crown’ as the
labia part. At this point the woman may feel a burning or stinging

Delivery of the fetal head signals the successful completion of the
fourth mechanism of labour (delivery by extension), and is followed by
the fifth and sixth mechanisms (restitution and external rotation).

A newborn baby with umbilical cord ready to be clamped

The second stage of labour will vary to some extent, depending on how
successfully the preceding tasks have been accomplished.

Похожие записи