Lecture difficult delivery due to uterine contractions

2021-03-21 12:00 AM

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).


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

The effect of uterine contractions changes the mother's side, the fetal side, the fetal appendage, pushes the fetus out of the uterus.

In a normally progressive labor, the uterine contraction must be normal, rhythmic, not too strong, not too weak. An abnormal uterine contraction when the contraction is too fast, too strong, or the base tone increases, or the contraction of the uterus is too thin, too weak.

Methods of assessing uterine contractions

Through the pain of the pregnant woman: In the pain of the uterus, strong contractions cause pain. This assessment is inaccurate because the contraction begins before the pain and lasts longer when the pain goes away. On the other hand, the pain depends on the psychological condition of each woman.

Manual assessment: Place the palm on the pregnant woman's abdomen and monitor the length of each contraction, the distance between the two contractions. This method is also not accurate, depends on subjective measurements and does not accurately assess the intensity of the uterine contractions. It can be applied at all treatment levels, initially assessing contractions.

Measuring uterine contractions with obstetric Monitoring: Helps us to accurately assess the intensity of each contraction, the frequency of contractions, the tonicity of the uterus through each stage of labor and also monitor the fetal heart. change in uterine contractions to detect pregnancy failure early.

The method of recording the ectopic contractions did not accurately measure the pressure of the partial uterine muscle and the pressure of the amniotic sac.

Internal recording method: Inserting a soft amniotic tube into the amniotic chamber over the cervix or through the abdominal wall of the mother to measure the intra-amniotic pressure, basal uterine tone, frequency, intensity of uterine contractions. The downside of this method is that it cannot determine the individual pressure of the uterine muscle and the long placement in the uterus also causes infection of the amniotic fluid, the technique is complicated so it is rarely used. Only for use in the case of the uterus with old surgical scars, premature rupture of amniotic fluid.

Microballons are inserted into the uterine muscle at different locations of the uterine muscle (horn, base, trunk, lower uterine segment across the abdominal wall to record contraction pressure in different areas of the uterus. , determine the origin of uterine contractions, change the contraction pressure and spread of the uterine contraction.

Characteristics of uterine contractions

Normal 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 the 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 reduction. 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.

Uterine contractions in labor

The contraction occurs spontaneously, without the wishes of the woman. The starting point of the contraction is located at one of the uterine horns. Usually there is only one starting point that acts and deflects the other. All contractions come from one point. The contraction or starts from the right horn of the uterus spread to the left, the speed of transmission is 2-3cm / s.

The contraction is cyclical and regular in nature. The contraction gradually increased, the contraction time gradually grew, the intensity also gradually increased.

A contraction of the uterus causes pain. Pain threshold depends on the woman. When the pressure of contraction reaches 25-30 mmHg, women feel pain. The faster and more intense the contraction of the uterus, the more painful it will be during the long contraction time. When there is anxiety, pain increases.

Uterine contraction of nature 3 decreases: The pressure decreases gradually from top to bottom, the rate of spreading down to the muscle part according to the rule of 3 decreases, the highest in the uterine horn, when reaching the outer hole of the cervix, the pressure is zero. , the contraction of the uterine muscle also decreases, in the body of the uterus contract longer than in the lower segment and in the lower part, the contraction of the cervix is ​​longer, the pressure decreases from top to bottom, the intensity is higher in the upper part. below.


At the beginning of labor, the cervix is ​​2cm

When the cervix is ​​completely open


Time (seconds)



Intensity (mmHg)


50-55 ;  60-70

Frequency (contraction / 10 minutes)



Activity (Montevideo)



Muscular tone of the uterus

8 mmHg

10-12 mmHg

Abnormal contractions

Uterine contractions increase

Increase the intensity of uterine contractions

The contraction duration is longer, the contraction amplitude is stronger, the distance between the two contractions is shorter than normal, meaning the contraction is too long, too strong, too fast.


The common cause is that the risk factors of the birth of the mother belong to the mother, such as abnormal pelvic abnormalities, and tumors of the striker. Pregnancy such as total fetal enlargement, abnormal stars, fetal deformity, multiple pregnancy.

Some cases are caused by using uterine inotropic drugs in case the uterus has a fibrous nucleus, a malformed uterus, or an underdeveloped uterus.

Due to nervousness, psychology, or anxiety and fear in pregnant women.

Often increased contraction intensity is accompanied by increased uterine muscle tone.

Consequences: There are many negative consequences for both mother and fetus. Increased contraction can slow the cervix to open slowly, most dangerous is the rupture of the uterus or rupture of the uterus, which is life-threatening for both mother and fetus. In pregnancy, a decrease in uterine circulation leads to pregnancy failure, or fetal death. Postpartum in cases of contraction prone uterine sputum.

Treatment attitude

If the cause is mechanical, the treatment is cesarean section, while waiting for surgery, it is necessary to give contraceptive drugs, and at the same time resuscitate the fetus by giving the mother oxygen, and 20% sweet serum infusion.

If an overdose of an inotropic drug is used, a careful review of the indications and dosage of the drug must be carefully reviewed.

If the disorder is caused by the starting point of the contraction, it is necessary to use contraction-reducing drugs, cut the contraction, and then adjust the contraction. If the adjustment is not possible, there are bad signs for both the mother and the fetus, a cesarean section is required when the conditions for vaginal abortion are not eligible.

Increased uterine muscle tone

In open cervical labor 2 cm, the basal tonicity is 8 mmHg. When the cervix is ​​completely open, the basal tonicity is 10 mmHg, and when forced to deliver is 12 mmHg.

If the basal tonicity increases, it will be difficult to distinguish the uterus during contraction, at rest, reducing the effect of the contraction. If the tone of the uterus is equal to the intensity of the contraction, then the uterus spasm, which can be dangerous for the fetus.


Long labor and juvenile morphology.

Underdeveloped uterus, uterus deformity, uterus in children compared to old age, or women easily irritated, afraid.


The uterus is spastic, the cervix narrows, opens slowly, causing labor to last long. Hypertonia associated with uterine contractility reduces vegetable uterine circulation, leading to fetal failure or fetal death.

Treatment attitude

Encourage pregnant women to rest assured.

Reduce contraction to reduce muscle tone, help the cervix open quickly, labor will progress normally. If the fetal failure is not corrected, then a cesarean section is required ineligible for vaginal delivery.

Premature peeling vegetables can be handled depending on the severe cases, even though the fetus is still dead, it is necessary to cesarean section.

Uterine contractions decreased

Decreased uterine contractions show short duration of each contraction, the space between contractions is thin and weak. Decreased contractions can be accompanied by hypotonia.


Systemic diseases of the mother such as heart disease, anemia, tuberculosis weaken the mother's condition.

The uterus, giving birth many times, prolonged labor, premature rupture of the amniotic fluid, premature rupture of the amniotic fluid

The uterus is too stretched in poly amniotic fluid, multiple pregnancy, the uterus has a fibrous nucleus.


During labor, remove cervical opening of the cervix, weak contractions cause the cervix to open slowly, so labor is prolonged. If the amniotic fluid breaks prematurely, it is more susceptible to infection of the amniotic fluid and pregnancy failure.

During the pregnancy period, the weak contraction makes the pregnancy impossible, so it is necessary to intervene with some procedures such as forxep or suction to remove the pregnancy, so it can cause trauma to the mother and baby.

During the period of vegetable book, if the contraction is weak, it can lead to uterine sputum causing bleeding, threatening the mother's life, so it is necessary to follow up early for timely treatment.

Treatment attitude

After eliminating other difficult birth defects, if the amniotic fluid breaks early, the contraction is weak for uterotonic drugs: oxytocin is infused with an intravenous drip. Adjust the amount of drug infusion according to uterine contractions - Poly amniotic fluid needs amniotic rays for the uterus to help less stretch the uterus contraction increase, if still weak, for the drug to increase contraction. If the amniotic fluid breaks for more than 6 hours, it is necessary to give antibiotic to whole body to prevent infection.

In the period of pregnancy, if the contraction is weak, sparse should increase contraction, combined with the weak force of the pregnant woman, it is possible to use forxep or suction to remove the pregnancy.

During the period of vegetable delivery, if the uterus contraction is weak or the uterus is giving birth many times, the uterus is too stretchy in poly amniotic fluid, multiple pregnancies need to prevent uterine expulsion by intravenous drip oxytocin until after the test is taken. vegetable 2 hours. After the vegetable book, if you are sure the uterus is clean for intramuscular ecgotamine. Following uterine control, oxytocin is injected directly into the uterine muscle.

When using an inotropic drug, it is necessary to have the right indications, the right technique, and to set up a close monitoring table on the mother and fetus to have timely management attitude when there is an incident. In pregnancy, oxytocin must continue to be infused until the uterus contracts well, creating a safe mass after birth.