Lecture of labor

2021-03-21 12:00 AM

Until now, people did not know clearly and completely the causes of contractions of labor. People have given many theories to explain, there are a number of theories accepted.


Labor is a process in which the fetus and placenta are removed through the uterus through the vagina.

A labor usually occurs after a gestation period from 38 (259 days) to 42 weeks (293 days) with an average of 40 weeks (280 days), at which time the fetus is mature and capable of living toxic. ectopic pregnancy.

Preterm birth is a condition in which a pregnancy is interrupted when it is viable. Preterm labor occurs between 28 weeks and 37 weeks gestation

Premature labor is a labor phenomenon occurring 2 weeks after the expected date of delivery. Called the old pregnancy when the gestational age is more than 42 weeks 

Stages of labor

3 phases, each period is long and short.

State 1

The period of cervical dilation, from the beginning of labor to the time when the cervix is ​​completely open, this stage is the longest stage of labor. The average duration of this period is 15 hours including:

Stage 1a: From the time the cervix begins to erase until the cervix opens 3 cm, it is called latent phase, time of 8 hours.

Stage 1b: From the time the cervix opens 3 cm to 10 cm (fully opened) called active phase, time 7 hours.

Phase 2

The period of pregnancy registration is from when the cervix is ​​fully opened until the pregnancy passes out, the average time is 30 minutes, up to 1 hour. This stage is performed by 2 factors: the strength of the uterus contraction and contraction of the abdominal wall muscles.

Stage 3

It is the period of vegetables, starting from the time the pregnancy takes out until the vegetables are peeled, down and the vegetables are taken out together with the vegetable film, with time of 15-30 minutes.

Causes of labor

Until now, people did not know clearly and completely the causes of contractions of labor. People have given many theories to explain, there are a number of theories accepted.

Prostaglandin (PG)

Prostaglandins are substances that can change the contractile activity of the uterine muscles. The production of PGF2 and PGE2 increases gradually during pregnancy and reaches high values ​​in amniotic fluid, membranes, and in the uterine muscles at the onset of labor. Reduced oxygen during labor increases prostaglandin synthesis. Prostaglandin is synthesized from the sheath and amniotic membranes.

Labor can be induced by injecting Prostaglandin regardless of the gestational age.

Prostaglandins are involved in cervical ripening by acting on the cervical collagen.

Estrogen and Progesterone

During pregnancy, estrogen increases the stimulation of smooth muscle fibers of the uterus and the rate of transmission of electrical activity, the uterine muscle becomes more susceptible to uterine contractions, especially with oxytocin. Estrogen increases the development of the uterine muscular layer and facilitates the synthesis of prostaglandins from the sheath and amniotic membranes. Progesterone has an inhibitory effect with contractions of the uterine muscle. The decrease in progesterone concentration in late pregnancy changes the ratio of Estrogen/progesterone (increased) that is responsible for labor.

The role of oxytocin

There has been an increase in the maternal posterior pituitary secretion of oxytocin during labor. However, oxytocin does not play an important role in inducing labor, but mainly accelerates the ongoing labor process.

Other factors

A gradual and excessive increase in the uterine muscle and an increased response to stimuli will induce labor.

Fetal factors: A fetus with incarnation or adrenal insufficiency usually prolong pregnancy, whereas if adrenal insufficiency will cause premature birth.

A contraction of the uterus

The contraction of the uterus is the driving force of labor.

Methods of studying uterine contractions

By hand: Place the palm of the hand on the pregnant woman's abdomen and monitor the length of each uterine contraction, the distance between the two contractions.

This method is not accurate and does not accurately assess the intensity of uterine contractions.

External recording method: Place a Murey drum at the base of the uterus and measure the pressure of the uterine contraction. The unit is in mmHg. This method measures the frequency and length of contractions but does not accurately measure the pressure of the partial uterine muscle and the pressure in the amniotic chamber.

Method of inscription: Insert a thin, soft amniotic tube into the amniotic fluid through the cervix or across the abdominal wall of the mother to measure the intra-amniotic pressure, the basal tone of the uterus, the frequency and intensity of the uterine contractions. bow.

Miroballons are inserted into the uterine muscle at different positions of the uterus, across the abdominal wall to record contraction pressure in different areas of the uterus, the starting point of uterine contractions, change the pressure of the contraction and diffusion of the uterine contraction.

Characteristics of uterine contractions

Pressure of uterine contractions in mmHg or in Kilo Pascal (KPa) (1mmHg = 0.133 KPa). Montevideo unit (UM) is calculated as the average contraction amplitude multiplied by the frequency of contractions (number of contractions per 10 minutes).

During the first 30 weeks of pregnancy, the uterus has no contractions, from 30 to 37 weeks uterine contractions may be more, reaching 50 UM. At the onset of labor, the uterine contraction is 120 UM, gradually increasing by 250 UM at the time of delivery.

One or two weeks before labor, the uterus has a milder, more rapid contraction than before, with a pressure of 10 - 15 mmHg called pain-free Hicks contractions.

The intensity of uterine contractions is measure at the moment of the highest uterine pressure of each contraction.

Basic tonicity of the uterine muscle: 5 - 15 mmHg.

The effect of uterine contractions = intensity of uterine contractions minus baseline tone.

The length of the uterine contraction is from the moment the uterus starts to contract until the end of the contraction, unit = seconds.

The frequency of uterine contractions increases gradually in frequency and intensity during labor.

The starting point of each contraction is located in 1 of the 2 horns of the uterus, usually the right horn in humans.

A contraction of the uterus causes pain when the pressure is 25-30 mmHg.

Uterine contractions have properties of 3 reductions. The contraction of the uterus from the uterus spreads to the base and body to the lower part and cervix.

The contraction time of the uterine muscle gradually decreases from top to bottom, the pressure of uterine contractions gradually decreases from top to bottom.

Characteristics of uterine contractions in labor

Uterine contractions occur spontaneously against the will of a person.

A contraction of the uterus is cyclical and regular in nature. The contractions of the uterus quickly increase, the distance between 2 contractions at the beginning of labor is 15-20 minutes, then shorter and shorter, at the end of stage I about 2-3 minutes.

The contraction of the uterus gradually lengthens, begins labor 15-20 seconds, reaches 30-40 seconds at the end of cervical dilation. The intensity of contractions gradually increases, the pressure of new labor contractions 30-35mmHg (120Um) gradually increases to 50-55 mmHg in the open cervical stage and in the gestational period up to 60-70 mmHg, equivalent to 250UM. Lying on the left side does not change basal uterine tonicity, but the intensity of uterine contractions increases by 10 mmHg and the frequency of contractions decreases.

A contraction of the uterus causes pain when the pressure reaches 25-30 mmHg. The pain occurs after uterine contractions and goes before uterine contractions, the stronger the contraction becomes more painful and the pain increases when the anxious woman is afraid.

A contraction of the uterus has 3 decreased properties: contraction pressure decreases from top to bottom, contraction time of uterine muscle decreases from top to bottom, spread of uterine contractions in the direction of the uterus from top to bottom.

Uterine contractions and abdominal wall contractions during the pregnancy period

In the second stage of labor, the uterine contraction combined with the contraction of the abdominal wall pushes the fetus out. The pressure of the uterine contraction at the end of stage II increases with the contraction of the abdominal wall causing the pressure in the amniotic chamber to increase to 120-150 mmHg.

Therefore, guiding the woman to correct labor is very valuable in giving birth.

Changes in the maternal, fetal and maternal side of the fetus as a result of uterine contractions

Change towards mother

Removal of cervical opening and lower segment formation

Erection: The normal cervix is ​​cylindrical with an inner and outer orifice.

Erasure is a gradual dilatation of the inner hole causing the cervix to change from a cylinder to a thin sheet. When the cervix is ​​erased, the cervical chamber along with the lower segment becomes the cervical canal - the segment.

Opening: It is a phenomenon that the extra cervical hole expands from 1cm until it is completely open to 10cm. Then the uterus opens straight with the vagina and forms the cervical - segment - vaginal canal. Time to erase cervical opening is irregular: from erase - open 4 cm about 8-10 hours. From 5 cm to open about 4-6 hours. The average opening speed is 1 cm/hour.

How quickly or slowly erased the cervix depends on:

The amniotic fluid head presses the cervix more or less.

The amniotic fluid is more or less sticky

Is the contraction of the uterus strong and synchronous enough?

Lower Uterine Formation: The lower uterine segment forms because the uterine waist is enlarged, elongated, and enlarged. When the sub uterine segment is completely formed 10cm.

There are differences between the rat and the chicken in cervical dilation. In comparison, the cervix is ​​erased and then opened, and when the crow is opened, the cervix is ​​both erased and opened. The opening time of rice stubs is faster than that and the maximum opening speed is 5-7 cm/hour.

Changes in perineum

Due to the pressure of uterine contractions, the fetal throne gradually descends in the subframe, the tip is cut off behind with the diameter of the uterus - the defiant from 9.5-11 cm. The enlarged perineal layer is twice as long as the posterior episiotomy. The anus has erased all folds.

Changes in fetal direction

The pressure of the uterus pushes the fetus out of the uterus according to the delivery mechanism.

During labor, the fetus has a mold bending phenomenon.

Cranial superposition: fetal skull shrinks in size by overlapping bones.

Formation of a serous tumor.

Serum tumor is pushed down to the lowest position of the fetus where the pressure is lowest. Serum tumors form only when the amniotic fluid has ruptured. Each person usually has its own location of serous tumor.

Changes in the appendage of the fetus

The contraction of the uterus causes the amniotic fluid to fall off, the amniotic fluid rushes down to form the amniotic sac or the end of the amniotic fluid.

There are types of amniotic fluid: flat amniotic fluid; bulging amniotic fluid; pear-shaped amniotic fluid.

Amniotic fluid: The amniotic fluid separating the amniotic fluid from the fetus is very thin due to the good regulation of the fetus.

Amniotic fluid: The amniotic fluid between the amniotic fluid and the fetus is thick, often cases the fetus is not rectified well.

Pear diseases: The amniotic fluid head pokes through the cervix and into the vagina even though the cervix is ​​open when the amniotic fluid loses the dilation which is encountered in stillbirth.

Effects of the amniotic fluid

Help the cervix to clear, open.

Protect the fetus from trauma.

When the amniotic fluid ruptures for> 6 hours there is a risk of retrograde infection from the vagina and amniotic fluid.

Forms of rupture of membranes

Broken amniotic fluid at the right time: When the cervix is ​​completely open.

Premature rupture of the amniotic fluid: It ruptures during labor, but the cervix is ​​not fully opened.

Premature rupture of membranes: Broken amniotic fluid during labor.

Vegetable peel and vegetable book: The contraction continues to appear after a period of physiological rest making the placenta and vegetable membrane out. The uterus is constricted to form a safe block within 2 hours, causing physiological embolism after the spinach leaves.

Other changes

During the contraction, the mother's breathing slows down and the pulse increases, the contraction goes back to normal.

About metabolism

Mother's body weight loss from 4-6 kg. The number of leukocytes increases during labor.


The bladder neck may be pulled up above the joint, the urethra is pulled high and squeezed between the fetal seat and the hip joint.

On the side of the fetus

The fetal heart changes during uterine contractions, the fetal heart speed up slightly when the new uterus contracts, then slow down during uterine contractions. In addition to uterine contraction, the fetus gradually returns to normal.

Labor time

In humans: normally 16-20 hours, in humans, the time is shorter, averaging 8-12 hours.

Labor for> 24 hours is a long-term one that can easily fail to conceive. The tired mother no longer has strength and easy procedure intervention.