Physiology of labor
Labor process was divided in to 3 stages. The first stage star when the uterus has enough
frequency, intensity, and duration to produce progressive landfall and dilatation of cervix. The
first stage is over when the cervix has opened completely (around 10 cm) so that enable the head
of the fetus through. The second stage star when the dilatation of the cervix was complete, and
over when the fetus was born. The third stage star as soon as the fetus outward, and over by
outward of the placenta and omniotic membrane.
Diagnosis of stage and phase of labour
Symptoms and Signs Stage Phase
• Cervix not dilated False labour/Not in
labour
• Cervix dilated less than 4 cm First Latent
• Cervix dilated 4–9 cm
• Rate of dilatation typically 1 cm per
hour or more
• Fetal descent begins
First Active
• Cervix fully dilated (10 cm)
• Fetal descent continues
• No urge to push
SecondEarly (non-
expulsive)
• Cervix fully dilated (10 cm)
• Presenting part of fetus reaches
pelvic floor
• Woman has the urge to push
Second Late(expulsive)
The third stage of labour begins with delivery of the baby and ends with expulsion of placenta.
Uterus activity differentiation
During labor, uterus’s form changes into two different parts. Upper segment contracts actively
become more thick during labor. The lower segment is passive compare with the upper segment,
and this part develop become delivery was which has very thin wall. Miometrium in the upper
segment doesn’t relax until reach the length before after contraction, but become constant in the
shorter length. But the strain still same like before contraction. Upper part of uterus contract
downward although when the volume decreases, so that miometrium strain still constant. The
last effect is strain the loose, by defend good condition that was gotten by fetus expulsion and
maintain uterus muscle stay adhere into uterus. As retraction consequences, all the next
contraction star in the place that left by contraction before, so that upper cavity of the uterus
becomes smaller in each contraction. Because shorten of muscle fiber continue in every
contraction, upper active segment of the uterus become thicker as long as first and second stage
and become very thick exact after fetus delivery.
Obliteration and Dilatation of cervix
Obliteration is shortening of cervix canal from length about 2 cm become just around orifice
with the edge near thin like a paper. When uterus contraction produces pressure to amniotic
membrane, hydrostatic pressure of amniotic membrane will dilate cervix canal.
Delivery of the fetus
Active contraction of the uterus of increasing strength, frequency, and duration cause passive
movement of the fetus down the birth canal. At the beginning of labour, the lie, presentation and
engagement of the fetus are assessed. As the labour progresses, the neck becomes fully flexed so
that the suboccipitobregmatic diameter is presenting.
Descent occurs when the head is engaged, followed by internal rotation to bring the occiput into
the anterior posterior when it reaches the pelvic floor. In the second stage of labour, the occiput
descends below the symphysis pubis and the movement of extension pushes the head forwards
and delivers the occiput. Increasing extension round the pubic bone delivers the face.
The fetal head normally engages in the maternal pelvis in an occiput transverse position, with the
fetal occiput transverse in the maternal pelvis
Occiput transverse positions
With descent, the fetal head rotates so that the fetal occiput is anterior in the maternal pelvis
(occiput anterior positions. Failure of an occiput transverse position to rotate to an occiput
anterior position should be managed as an occiput posterior position.
Occiput anterior positions
The head of the baby come in to through pelvic rim can be divided into 3 situations.
Sinklitismus, if the axis direction of fetus’s head is straight upright with pelvic rim area.
Asinklitismus, if the axis direction of fetus’s head is oblique to pelvic rim area. Anterior
asinklitismus according to Naegele is when the axis direction of fetus’s head make sharp angle to
front by pelvic rim. Posterior asinklitismus according to Litzman ia when the condition is opposit
Delivery of the head brings the shoulder into pelvic cavity, with the head oblique to the line of
the shoulders. Restitution occurs: the head rotates to the natural position in relation the shoulders.
Finally, In the process of external rotation continuing descent and rotation of the shoulders
brings their widest diameter into the anteroposterior diameter of the pelvic outlet. This enables
the anterior shoulder to pass under the pubis. Lateral flexion of the fetus delivers the posterior
shoulder and the rest of the body follows.
As soon as the baby born, amplitude of his was same high, just the frequency decrease. Because
of this his, uterus will decrease in size so that placenta sticking to uterus wall will be free. The
sticking of placenta from uterus wall can be started from 1) middle (central according to
Schultze); 2) edge (marginal according to Mathew-Duncan); 3) combination 1 and 2. The most
one is according to Schultze. Generally the third stage happened about 6 till 15 minutes. The
high of uterus after the third stage about 2 fingers below umbilicus.
By: Tri Mardiyana
Source :
Ilmu kebidanan (Kusnarman Keman)
Crash Course: Obstetrics and Gynaecology
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