MECHANISM OF LABOR IN ENGLISH

                                                   

                                  MECHANISM OF LABOR IN ENGLISH

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Mechanism of labor

The series of movements that occur on the head in the process of adaptation during its journey through the pelvis is called mechanism of labor. It is just a guide for midwives may not suite to every delivery because each labour is unique.

In this class we will discuss mechanism for normal labor in which-

• the lie is longitudinal

• the presentation is cephalic

• the position is right or left occipitoanterior

• the attitude is one of good flexion

• the denominator is the occiput

• the presenting part is the posterior part of the anterior parietal bone.

 

Mechanism of labor can be learnt with the world EDFICEREE

(1) Engagement,

(2) Descent,

(3) Flexion,

(4) Internal rotation,

(5) Crowning,

(6) Extension,

(7) Restitution,

(8) External rotation

(9) Expulsion of the Shoulder/trunk.

 

(1) Engagement- engagement is the process by which the widest part of the baby's head (the biparietal diameter) passes through the pelvic inlet, meaning it has descended into the mother's pelvis. Successful engagement indicates that the pelvis is large enough for the baby to descend further

 (2) Descent- Descent is the process where the baby's head, or presenting part, moves downward through the maternal pelvis and into the birth canal. If there is no undue bony or soft tissue obstruction, descent is a continuous process. It is slow or insignificant in first stage but pronounced in second stage. It is completed with the expulsion of the fetus.

 (3) Flexion- flexion at neck is achieved either due to the resistance offered by the cervix, the walls of the pelvis or by the pelvic floor. It has been seen that flexion precedes internal rotation or at least coincides with it. Flexion is essential for descent, since it reduces the shape and size of the plane of the advancing diameter of the head.

 (4) Internal rotation- Internal rotation in labor is the process where the fetal head pivots inside the mother's pelvis, typically from an occipitolateral (ROA or LOA) position to an occipitoanterior position, to align its longest diameter with the widest part of the pelvic outlet. 

 (5) Crowning- Crowning is a stage in the mechanism of labour where the largest part of the baby's head is visible through the vaginal opening and no longer recedes between contractions. It occurs in the second stage of labour after the cervix is fully dilated.

 (6) Extension- Delivery of the head takes place by extension through “couple of force” theory. The driving force pushes the head in a downward direction while the pelvic floor offers a resistance in the upward and forward direction. The downward and upward forces neutralize and remaining forward thrust helping in extension

 (7) Restitution- It is the visible passive movement of the head due to untwisting of the neck sustained during internal rotation. Movement of restitution occurs rotating the head through one-eighth of a circle in the direction opposite to that of internal rotation

 (8) External rotation- It is the movement of rotation of the head visible externally due to internal rotation of the shoulders. As the anterior shoulder rotates toward the symphysis pubis from the oblique diameter, it carries the head in a movement of external rotation through one-eighth of a circle in the same direction as restitution.

 (9) Expulsion of the Shoulder/trunk.- After the shoulders are positioned in anteroposterior diameter of the outlet, further descent takes place until the anterior shoulder escapes below the symphysis pubis first. By a movement of lateral flexion of the spine, the posterior shoulder sweeps over the perineum. Rest of the trunk is then expelled out by lateral flexion.

PHYSIOLOGY OF LABOR IN ENGLISH

                                                     

                                  PHYSIOLOGY OF LABOR IN ENGLISH

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Physiology of Labor-

Physiology of labor is a Series of events that take place in the genital organs in an effort to expel the viable products of  conception  into the outer world. It includes events in first stage of labor, events in second stage of labor and events in third stage of labor.

Events in first stage of LABOR-

Physiological events in first stage of labor includes-

(1) Contractions of uterus- there are wide variations in frequency, intensity and duration of contractions, having following patterns.

Ø  There is good synchronization of the contraction waves from both halves of the uterus and also between upper and lower uterine segments.

Ø  There is fundal dominance of contractions that diminish gradually in duration and intensity

Ø  through midzone down to lower segment. It takes about 10–20 seconds.

Ø  The waves of contraction follow a regular pattern.

Ø  The upper segment of the uterus contracts more strongly and for a longer time than the lower 

Ø  Intra-amniotic pressure rises beyond 20 mm Hg during uterine contraction.

Ø  Good relaxation occurs in between contractions to bring down the intra-amniotic pressure to less than 8 mm Hg. Contractions of the fundus last longer than that of the midzone.

During uterine contractions the patient experiences pain which is situated more on the hypogastric region, often radiating to the thighs.  causes of pain are:

(a)    Myometrial hypoxia during contractions 

(b)    stretching of the peritoneum over the fundus,

(c)    stretching of the cervix during dilatation,

(d)    stretching of the ligaments surrounding the

uterus and (e) compression of the nerve ganglion.

Tonus : It is the intrauterine pressure in between contractions. During pregnancy, as the uterus is inactive, the tonus is of 2–3 mm Hg. During the first stage of labor, it varies from 8 mm Hg to 10 mm Hg. The factors which affects the tonus are:

(i) Contractility of uterine muscles,

(ii)intra-abdominal pressure, and

(iii) overdistension of uterus as in twins and hydramnios.

Intensity : The intensity of uterine contraction describes the degree of uterine systole. The intensity gradually increases with advancement of labor until it becomes maximum in the second stage during delivery of the baby. Intrauterine pressure is raised to 40–50 mm Hg during first stage and about 100–120 mm Hg in second stage of labor during contractions. 

Duration : In the first stage, the contractions last for about 30 seconds initially but gradually increase in duration with the progress of labor. Thus in the second stage, the contractions last longer than in the first stage.

Frequency: In the early stage of labor, the contractions come at intervals of 10–15 minutes. The intervals gradually shorten with advancement of labor until in the second stage, when it comes every 2–3 minutes.

(2) Retractions of uterus- Retraction is a phenomenon

of the uterus in labor in which the muscle fibers are permanently shortened. the uterine muscles have this property to become shortened once and for all.

Effects of retraction-  — Essential property in the formation of lower uterine segment and dilatation and effacement of the cervix. — To maintain the descent of the presenting part made by the uterine contractions and to help in ultimate expulsion of the fetus. — To reduce the surface area of the uterus favoring  separation of placenta. — Effective hemostasis after the separation of the placenta.

(3) Dilatation of the cervix-   Dilatation of cervix starts at onset of labor. In multipara it may start a little earlier.

Predisposing factors which favor smooth dilatation are—

(a) softening of the cervix,

(b) fibromusculoglandular hypertrophy,

(c) increased vascularity, 

(d) accumulation of fluid in between collagen fibers,

(e) breaking down of collagen fibrils by enzymes collagenase and elastase, and

(f) Increase in hyaluronic acid, decrease in dermatan sulfate in the matrix of the cervix. These are under the action of hormones—estrogen, progesterone and relaxin

Actual factors which favor smooth cervical dilatation are—

Uterine contraction and retraction-  Each uterine contraction, not only the cervical canal is opened up from above down but also it becomes shortened and retracted.

Fetal axis pressure: In labor with longitudinal lie and with well-fitted (flexed) fetal head on the cervix, fetal vertebral column is straightened by the contractions of the uterus. This allows the fundal strong contraction force to be transmitted through the fetal podalic pole and vertebral column to the well-fitted fetal head. This causes mechanical stretching of the lower segment and dilatation of the cervical canal.

Bag of membranes:  During uterine contractions the bag of membranes or bag of waters (forewater)  generate hydrostatic pressure that in turn dilate the cervical canal .

EFFACEMENT OF CERVIX:

Effacement is the process by which the muscular fibers of the cervix are pulled upward and merges with the fibers of the lower uterine segment. The cervix becomes thin during first stage of labor or even before that in primigravidae

LOWER UTERINE SEGMENT: Before the onset of labor, there is no complete anatomical or functional division of the uterus. During labor the demarcation of an active upper segment and a relatively passive lower segment is appeared. This demarcation is known as physiological retraction ring

Events in second stage of LABOR-

The second stage begins with the complete  dilatation of the cervix and ends with the expulsion of the fetus. This stage is concerned with the descent and delivery of the fetus through the birth canal. Second stage has two phases:

(1) Propulsive—from full dilatation until head touches the pelvic floor.

(2) Expulsive—since the time mother has irresistible desire to “bear down” and push until the baby is delivered.

In second stage cervix is fully dilated and  the membranes usually rupture and there is escape of good amount of liquor amnii. The volume of the uterine cavity is thereby reduced. Simultaneously, uterine contraction and retraction become stronger. The uterus becomes elongated during contraction. The elongation is partly due to the contractions of the circular muscle fibers of the uterus to keep the fetal axis straight.

Delivery of the fetus is accomplished by bearing down effort that is the downward thrust  provided by uterine contractions supplemented by voluntary contraction of abdominal muscles against the resistance offered by bony and soft tissues of the birth canal.

 

Events in third stage of LABOR-

The third stage of labor is the phase of placental separation; its descent to the lower segment and finally its expulsion with the membranes.

Mechanism of separation: Marked retraction reduces the surface area at the placental site to about its half. But as the placenta is inelastic, it cannot keep pace with such an extent of diminution resulting in its buckling

shearing force is instituted between the placenta and the placental site which brings about its ultimate separation. The plane of separation runs through deep spongy layer of decidua basalis so that a variable thickness of decidua covers the maternal surface of the separated placenta. There are two ways of separation of placenta (1) Central separation  and (2) Marginal separation

(1) Central separation – Detachment of placenta from its uterine attachment starts at the center resulting in opening up of few uterine sinuses and accumulation of blood behind the Placenta. With increasing contraction, more and more detachment occurs facilitated by weight of the placenta and retroplacental blood until whole of the placenta gets detached.

(2) Marginal separation - Separation starts at the margin as it is mostly unsupported. With progressive uterine contraction, more and more areas of the placenta get separated. Marginal separation is found more frequently.

SEPARATION OF THE MEMBRANES: The membranes, which are attached loosely in the active part, are thrown into multiple folds. Those attached to the lower segment are already separated during its stretching.

EXPULSION OF PLACENTA: After complete separation of the placenta, it is forced down into the

flabby lower uterine segment or upper part of the vagina by effective contraction and retraction of the

uterus. Thereafter, it is expelled out either by voluntary contraction of abdominal muscles (bearing down efforts) or by manual procedure

TYPES OF ABORTION part 2 IN ENGLISH

                                                      

                                  TYPES OF ABORTION part 2 IN ENGLISH

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Types of Abortions PART 2

Missed abortion-

When the fetus is dead and retained inside the uterus for a variable period, it is called missed miscarriage. The causes of prolonged retention of the dead fetus in the uterus are not clear. Beyond 12 weeks, the retained fetus becomes macerated or mummified. The liquor amnii gets absorbed and the placenta becomes pale, thin and may be adherent.

Clinical manifestations-

The patient usually presents with features of threatened miscarriage followed by:

(1) Persistence of brownish vaginal discharge.

(2) Disappearance of pregnancy symptoms

(3)Retrogression of breast changes.

(4) Cessation of uterine growth which in fact becomes smaller in size.

(5) Non-audibility of the fetal heart sound even with Doppler ultrasound if it had been audible before.

(6) On PV examination cervix feels firm

(7) Immunological test for pregnancy becomes negative.

Management-

If pregnancy is less than 12 weeks: (i)  Medical

Management includes insertion of Prostaglandin E1 (misoprostol) 800 mg vaginally in the posterior fornix and repeated after 24 hours if needed. Expulsion usually occurs within 48 hours.

(ii) Suction evacuation or dilatation and evacuation is done either as a definitive treatment or it can be done when the medical method fails

If pregnancy is more than 12 weeks:

(a) Prostaglandin E1 analog (misoprostol) 200 μg tablet is inserted into the posterior vaginal fornix every 4 hours for a maximum of 5 times.

(b) Oxytocin—10–20 units of oxytocin in 500 mL of normal saline at 30 drops/min is started. If fails, escalating dose of oxytocin to the maximum of 200 mlU/min may be used with monitoring.

(c) Many patients need surgical evacuation following medical treatment after ultrasonography. 

(d) Dilatation and evacuation is done once the cervix becomes soft with use of PGE1. Otherwise cervical canal is dilated using the mechanical dilators or by laminaria tent. eacuation of the uterine cavity is done thereafter slowly.

Septic Abotion-

Any abortion associated with clinical evidences of infection of the uterus and its contents is called septic abortion. It is considered septic abortion  when there are: (1) rise of temperature of at least 100.4°F (38°C) for 24 hours or more, (2) offensive orpurulent vaginal discharge and (3) other evidences of pelvic infection such as lower abdominal pain and tenderness.

               Causes and Risk factors-

Main factor causing septic abortion is unsafe abortion technique by unqualified and unauthorized person. While the majority of cases, the infection occurs following illegal induced abortion but infection can occur even after spontaneous abortion.  by the sepsis are usually those normally present in the vagina (endogenous). The microorganisms are:-

(a)    Anaerobic—Bacteroides group (fragilis), anaerobic Streptococci, Clostridium welchii and tetanus bacillus.

(b)     Aerobic—Escherichia coli (E. coli), Klebsiella, Staphylococcus, Pseudomonas and group A beta-hemolytic Streptococcus (usually exogenous), methicillin-resistant Staphylococcus aureus

Clinical manifestations-

Depending upon the severity the clinical picture varies widely. These includes-

•        „„The woman looks sick and anxious

•        „„Temperature: >38°C

•        „„Chills and rigors (suggest-bacteremia)

•        „„Persistent tachycardia ≥ 90 bpm (spreading infection)

•        „„Hypothermia (if in shock) < 36°C

•        „„Abdominal or chest pain

•        Tachypnea (RR) > 20/min

•        „„Impaired mental state

•        „„Diarrhea and/or vomiting

•        „„Renal angle tenderness

Diagnostic Investigations-

(1) Cervical or high vaginal swab is taken prior to internal examination for—

(a)    culture in aerobic and anaerobic media to find out the dominant microorganisms,

(b)     sensitivity of the microorganisms to antibiotics and

(c)     smear for Gram stain.

 (2) Blood for hemoglobin estimation, total and differential count of white cells, ABO and Rh grouping.

(3) Urine analysis including culture.

(4) Ultrasonography of pelvis and abdomen to detect intrauterine retained products of conception

(5) Blood culture

(6) Serum electrolytes

Cinical Grading-

Septic abortions are of three types as per severity-

Grade I: The infection is localized in the uterus.

Grade II: The infection spreads beyond the uterus to the parametrium, tubes and ovaries or pelvic  peritoneum.

Grade III: Generalized peritonitis and/or endotoxic shock or jaundice or acute renal failure.

Management-

In case of Grade I:

(1)Broad spectrum Antibiotics  to control infection.

(2) Prophylactic anti gas gangrene serum of 8,000 units and 3,000 units of anti tetanus serum

intramuscularly are given if there is a history of unsafe abortion.

(3) Analgesics and sedatives as per need.

 (4)Blood transfusion is given to improve anemia and body resistance.

(5)Evacuation of the uterus: As abortion is often incomplete, evacuation should be performed at a convenient time within 24 hours following antibiotic therapy.

In case of Grade II:

(1)Broad spectrum Antibiotics  to control infection. Empirical therapy is started first and is changed when culture sensitivity report is available including Piperacillin-tazobactam and carbapenems:.

(2) Prophylactic anti gas gangrene serum of 8,000 units and 3,000 units of anti tetanus serum intramuscularly are given if there is a history of unsafe abortion.

 (3) Analgesics and sedatives as per need.

(4)Blood transfusion is given to improve anemia and body resistance.

(5) Evacuation of the uterus—Evacuation should be withheld for at least 48 hours when the infection is controlled and is localized, the only exception being excessive bleeding.

In case of Grade III:

(1) Clinical monitoring: To note pulse, respiration, temperature, urinary output and progress of the pain, tenderness and mass in lower abdomen.

(2) Broad spectrum Antibiotics  to control infection. Empirical therapy is started first and is changed when culture sensitivity report is available including Piperacillin-tazobactam and carbapenems.

(3) Prophylactic anti gas gangrene serum of 8,000 units and 3,000 units of anti tetanus serum intramuscularly are given if there is a history of unsafe abortion.

(4) Supportive therapy is directed to treat generalized peritonitis by gastric suction and intravenous crystalloids infusion. Management of endotoxic shock or renal failure.

(5)Patient may need intensive care unit management in case of respiratory, cardiovascular and kidney problems appear.

(6) Laprotomy with Removal of the uterus should be done irrespective of parity. Adnexa is to be removed or preserved according to the pathology found. Thorough inspection of the gut and omentum for evidence of any injury is mandatory

ONSET OF LABOR IN ENGLISH

                                             

                                  ONSET OF LABOR IN ENGLISH

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ONSET OF LABOR-

 

Labor-

Series of events that take place in the genital organs in an effort to expel the viable products of  conception (fetus, placenta and the membranes) out of the womb through the vagina into the outer world is called Labor.

Labor (EUTOCIA) is called normal following criteria are fulfilled-

(1) Spontaneous in onset and at term.

(2) With vertex presentation.

(3) Without undue prolongation.

(4) Natural termination with minimal aids.

(5) Without having any complications affecting the       health of the mother and/or the baby.

 

Cause of onset of labor

There is no clarity about what causes onset of labor still some theories are-

Uterine distension: Stretching effect on the myometrium by the growing fetus and liquor amnii can explain the onset of labor at least in twins or poly-hydramnios.

Uterine stretch increases gap junction proteins, receptors for oxytocin and specific contraction associated proteins (CAPs).

Feto-placental contribution: fetal hypothalamic-pituitary- adrenal axis-  Just before onset of labor there is increased CRH  in fetal hypothalamus→ increased release of ACTH from fetal pituitary and→ increased cortisol secretion from fetal adrenals → accelerated. This event leads to production of estrogen and prostaglandins from the placenta

This estrogen — Increases the release of oxytocin from maternal pituitary. — Promotes the synthesis of myometrial receptors for oxytocin, prostaglandins and increase in gap junctions in myometrial cells.

— Accelerates lysosomal disintegration in the decidual and amnion cells resulting in increased prostaglandin (PGF2α) synthesis. — Stimulates the synthesis of myometrial contractile protein—actomyosin 

  and  Increases the excitability of the myometrial cell membranes.

Progesterone:   Progesterone levels  fall before labor (due to fetal cortisol and de-hydro-epi-androsterone sulfate (DHEA-S) . Change in the estrogen : progesterone ratio rather is linked with prostaglandin synthesis.

Prostaglandins: Prostaglandins are the important factors, which initiate and maintain labor.

 

Pre Labor Stage-

PRELABOR: (premonitory stage): The premonitory stage may begin 2–3 weeks before the onset of true labor in primigravidae and a few days before in multiparae. The features are inconsistent

and may consist of the following:

•        Lightening

•        Cervical changes

•        Appearance of false labor pain

 

Lightening-

A few weeks prior to the onset of labor especially in primigravidae, the presenting part sinks into the true pelvis. It is due to active pulling up of the lower pole of the uterus around the presenting part. 

This diminishes the fundal height and hence minimizes the pressure on the diaphragm. It is a  welcome sign as it rules out cephalopelvic disproportion and other conditions preventing the head from entering the pelvic inlet.

Cervical changes-

Cervical changes: A few days prior to the onset of labor, cervix becomes ripe. A ripe cervix is

(a)    soft,

(b)    80% effaced (<1.5 cm in length),

(c) Admits one finger easily, and

(d) Cervical canal is dilatable.

Appearance of False labor pain-

False labor pain is –

      (i)          Dull in nature,

(ii) confined to lower abdomen and groin,

(iii) not associated with hardening of the uterus,

(iv) they have no other features of true labor  pain 

(v) usually relieved by enema or sedative.

 

Identifying the onset of labor-

The onset of labor is a process and is very difficult to identify exactly when the painless (sometimes painful) contractions of pre-labour develop into the progressive rhythmic contractions of actual labour. Onset of labor is assumed to start when rhythmic pattern of contraction starts and results in effacement and dilatation

True labor pain is : (i) Painful uterine contractions at regular intervals, (ii) frequency of contractions increase gradually, (iii) intensity and duration of contractions increase progressively, (iv) associated with “show”, (v) progressive effacement and  dilatation of the cervix, (vi) descent of the presenting part, (vii) formation of the “bag of forewaters” and (viii) not relieved by enema or sedatives.

Show: With the onset of labor, there is profuse cervical secretion. Simultaneously, there is slight oozing of blood from rupture of capillary vessels of the cervix and from the raw decidual surface caused by separation of the membranes due to stretching of the lower uterine segment. Expulsion of cervical mucus plug mixed with blood is called “show”.

Formation of bag of waters- Due to stretching of the lower uterine segment and With the dilatation of the cervical canal, the lower pole of the fetal membranes becomes unsupported and tends to bulge into the cervical canal. As it contains liquor, which has passed below the presenting part, it is called “bag of waters”.