LaborLabor

This is the process by which products of conception (fetus, placenta, cord

and membranes) are expelled from the uterus. It is defined as the progressive

effacement and dilatation of the uterine cervix, resulting from rhytmic

contarctions of the uterine musculature

Changes in late pregnacy which prognosticate labor:

• Braxton-Hick’s contractions

• lightening

• bloody show

Uterine contractions without effacement and dilatation of the cervix occur normally in the third

trimester of pregnancy and are termed Braxton-Hicks contractions.

Their number and intensity becomes greater as the patient approaches term. Sometimes they result in the patient’s perception of discomfort and cause so called „false labor” which doesn’t change the status

of the cervix (its length and dilatation)

Each contraction has three phasesEach contraction has three phases:

• increment - the intensity of the contraction increases

• acme - the contraction is at its high

• decrement - the intensity of the contraction diminshes

Lightening - (2-3 weeks before labor) It is the result of fetal head descending into the pelvis. The

patient reports a change in the shape of her abdomen and the sensation that the baby has gotten less heavy. As the bladder is compressed by the fetal head there

may be more frequent urination. The patient may also notice an easier time breathing, because there is

less pressure on the diaphragm.

Bloody show - (1-2 days before labor) this is the passage of blood-tinged (pink) mucus from vagina

which is the result of begining of the cervical effacement and extrusion of mucus from the

endocervical glands.

LIE = SITUSIt is the relation of the long axis of the

fetus with the maternal long axis

• longitudinal (99%) when the axes are parallel

• transverse when the axes cross at 90° angle

• oblique when the axes cross at 45° angle

Presentation is determined by „the presenting part” i.e. the portion of the fetus lowest in the birth canal

In longitudinal lie, the presenting part is either cephalic (96%) or breech (3%)

Position

• it is the relation of the fetal presenting part to the right or left side of the maternal pelvis or

• it is the relation of fetal spine to the right or left side of mother’s body Position I - left Position A – anterior Position II - right Position B - posterior

The pelvis is formed by five bones: the ilium, the ischium, the pubis, the sacrum, the coccyx and the

ligaments connecting them.

The ilium, the ischium and the pubis form the lateral and anterior boundaries of the pelvis. The sacrum and coccyx form the posterior wall of the pelvis.

The pelvis may be divided into:

1.The false pelvis - the upper part - which is seldom involved in the problems of labor2.The true pelvis - the lower part - which formes the bony canal through which the

baby must pass during delivery

The pelvis inlet divides the false pelvis from the true pelvis

Patient ought to come to the hospital if:

• uterus contractions occur approximately every 10 minutes for at least two hours

• there is a sudden gush of fluid or a constant leakage of fluid (rupture of membranes)

• there is some bleeding

• there is significant decrease in fetal movements

At the time of initial evaluation at the hospital the physician must:

• at first auscultate fetal heart tones • determine the nature and frequency of the uterus

contractions• determine the possibility of spontaneous rupture

of membranes• examine the gravid abdomen by Leopold

maneuvers• perform the vaginal examination

At the time of initial evaluation at the hospital the physician must reviev the

prenatal records to:

• identify complications of pregnancy up to that point

• confirm gestational age to differentiate preterm labor from labor at term, if necessary by use of USG

• review laboratory informations

1.The first Leopold maneuver determines what occupies the fundus (it helps to determine the lie and presentation)

2.The second Leopold maneuver determines location of small parts

(it is used to determine the position)

Using one hand to steady the fetus, the fingers of the other hand are used to palpate either the firm, long fetal spine or the various shapes and movements indicating fetal small parts (hands and feet)

3.The third Leopold maneuver identifies descent of presenting partSuprapubic palpation identifies the presenting part as the fetal head which is relatively mobile, or a breech which moves the entire body

4.The fourth Leopold maneuver identifies the cephalic prominenceAs long as the cephalic prominence is easily palpable, the vertex is not likely to have descended to 0 station (linea interspinalis, level of ischial spines)

Vaginal examination consists of:

- speculum examination- digital examination

!!! In every case of vaginal bleeding the vaginal examination should be done with extreme care, only by use of speculum, because of the risk of

disrupting a placenta previa !!!

The digital portion of vaginal examination allows the examiner to determine :

• - the degree of cervical effacement (from 3 to 0 cm)

• - the degree of cervical dilatation (from 0 to 10 cm)

• - the consistency of the cervix (firm, medial, soft)

• the position of the cervix in vagina (anterior, medial, posterior)

• the fetal station determined by identifying the foremost point of the fetal presenting part relative to the level of the ischial spines

The degree of engagement (in cm relative to the level of ischial spines)

• If the leading point of the presenting part is palpable at the pelvic inlet or above, it is called -4 station (floating)

• If the leading point of the presenting part is palpable lower but above the level of ischial spines it is called respectively -3, -2 or -1 station (fixed)

• If the leading point of the presenting part has reached the level of the ischial spines, it is termed 0 station. The largest diameter of presenting part is in the inlet (engaged)

The degree of engagement (in cm relative to the level of ischial spines)

• Descent of the leading point of the presenting part below the line of ischial spines is defined respectively as +1, +2, +3 . The largest diameter of presenting part is between the inlet plane and maximum depth of pelvis (midplane)

• If the presenting part is deep in pelvis and its leading point +4 or +5 it is called on perineum

The clinical significance of the fetal head presenting at 0 station is that the biparietal diameter of the fetal head (9,5-10 cm - the greatest transverse diameter of the fetal skull), has negotiated the pelvic inlet

Stages of labor

• The first stage (the period of dilatation and effacement) is the interval between the onset of labor (from the begining of regular contracions which occur every 10 minutes, from the moment of rupture of membranes) and full cervical dilatation (10 cm) - the latent phase which comprises cervical

effacement and early cervical dilatation (to 3-4 cm) - the accelerated phase (from 5 to 7 cm) - the transition phase (from 8 to 10 cm)

Stages of laborThe second stage (the period of expulsion) lasts from complete cervical dilatation till the delivery of the infant

The third stage (the placental stage) begins immediately after delivery of the infant and ends with the delivery of the placenta

The fourth stage is defined as the early postpartum period of approximately 2 hours after delivery of the placenta. During this period the patient undergoes significant physiologic adjustment and must be under close medical control

During the first stage of labor frequency of contractions rises from 1/10 min. to 5/10 min.

The contractions gradually become more frequent and regular. They also become

longer (60 s) and stronger

As the contractions continue through the first stage of labor, a pull is exerted on the cervix. The pressure of the baby’s presenting part (head) against the cervix

stimulates the release of the hormone oxytocin, which in turn stimulates further contractions.

As the upper portion of the uterus contracts, the lower portion relaxes, allowing the baby to descend further

toward the vagina.

If the fetal membranes don’t rupture spontaneously, sometimes (often) in the active phase of labor

(dilatation > 4-5 cm) we perform amniocentesis :

• to intensify uterine contractions• to insert intrauterine pressure catheter or a

fetal scalp monitor• to state the presence or absence of

meconium in amniotic fluid• to state the presence of blood in amniotic

fluid

Sometimes sponatneous (and rarely artificial rupture of membranes) may cause some risk:

- umbilical cord prolapse may occur if rupture of the membranes takes place before engagement of the presenting fetal part (fetal heart tones should be assesed after rupture of membranes in any case)

- icidence of infection may be increased if labor is prolonged, because there is an entry for bacteria - in some cases abruption of the placenta occurs

Mechanism of labor refers to the changes of the position of the fetus and movements of its head during the passage through the birth canal. These movements are accomplished by the forceful contractions of the uterus. The long diameter of the inlet of the pelvis is side to side. The long diameter of the outlet is from front to back. Therefore, the baby’s head must turn 90 degrees to emerge from the outlet. During normal cephalic labor the occipital portion of the fetal head is the lower-most part in maternal pelvis and rotates toward symphysis pubis.

Movements of the fetal head during its passage through the birth canal

• engagement

• descent

• flexion

• internal rotation

• extension

• external rotation

• expulsion

Engagement is defined as descent of the biparietal diameter of the head to the level of the pelvic inlet.

Clinically it is diagnosed by palpation of the leading point of the presenting part in the level of ischial

spines (0 station).

In multiparas engagement sometimes does not occur until dilatation of the cervix begin.

In primiparas it often occurs in the last days of pregnancy causing the feel of lightening (2-3 weeks)

Descent of the presenting part is a necessary for the successful completion of passage through the

birth canal.It is the continous progress of the fetus as it passes through the birth canal. It is brought about by the

downward pressure of uterine contractions.The greatest rate of descent occurs during the latter

portions of the first stage of labor and during the second stage of labor

Flexion of the fetal head allows for the smallest diameters of the fetal head (suboccipito-bregmatic

plane 32 cm of circumference) to present to the maternal pelvis. Flexion occurs when fetus descends and the head encounters resistance. During flexion

the head of the fetus is bent forward causing its chin to rest on its sternum (breastbone). Flexion is

important because the narrowest part of the head must enter the pelvic outlet.

Internal rotation facilities presentation of the optimal diameters of the fetal head to the bony pelvis.

It is the rotating of the head of the fetus 90 degrees from the transverse to the long diameter of the pelvis.

In normal labor the head rotates with its occiput toward

symphysis pubis.

This movement takes place mainly during the second stage of labor.

Extension of the fetal head occurs as it reaches the introitus and is stopped under the pubic arch. To

accomodate to the upward curve of the birth canal, the flexed head now extends

External rotation occurs after delivery of the head as the head rotates back 90 degrees from the long to the

transverse diameter of the pelvis relative to its shoulders

Expulsion is the final delivery of the fetus from the birth canal. It is delivery of the shoulders and the rest

of the body

Management of labor - general rules

- the patient shouldn’t be left without care for any significant length of time

- supporting person may be allowed to remain with the patient throughout the labor and

delivery process in most cases

Management of labor

• maternal vital signs should be taken at least every 30 minutes in the first stage of labor (pulse, blood pressure, respiratory rate, temperature, urine output)

• the patient should be given nothing by mouth except for sips of water or other clear liquids

• an intravenous line is always inserted at the admission to the delivery room to provide hydration or give drugs

Management of labor

• during labor, descent of the presenting part of the fetus causes elevation of the bladder which results in the patient having difficulty urine voiding. Therefore the patient should be encouraged to void frequently. In the end of the first stage or in the second stage of labor catheterisation of the bladder may be necessery

• the use of cleansing enema to empty the lower part of the digestive tract is indicated but not obligatory

Management of labor

• in the first stage of labor the position of the patient depends on her choice (sitting, lying or walking)

• in the second stage of labor we prefer „lying on the back” position

Management of labor• in the first stage of labor auscultation of the FHR

should be performed at least every 15 minutes by stetoscope or UDT. In our Clinic we generally use periodical electronic fetal monitoring (KTG) in low-risk pregnancies. In the cases of high risk we perform continious fetal monitoring

• in the second stage of labor fetal heart rate auscultation should be performed after each uterine contraction !!

Management of labor - drugs

• analgesic and anestetic agents may affect the latent stage of labor - they should generally not be used until the active phase of labor

• when they are used in the end of the first stage of labor they may couse neonatal depresion

Management of labor

• evaluation of the patients progress of labor is accomplished by means of a series of pelvic examinations with average for every two hours

• before every vaginal examination the perineum is cleansed with sterile solution and the examination is performed with sterile glove

Vaginal examination during labor should identify

• cervical dilatation• cervical effacement• station of the presenting part• position of the presenting part• status of the membranes

These findings should be noted graphillicaly on the hospital record (partogram)

In the second stage of labor patients report the need of push which accompanies the contractions. During the contraction voluntary maternal effort (pushing) can be added to the involuntary contractile forces of

the uterus to facilitate delivery of the fetus.

At the pik of each contraction, the mother is encouraged to take a deep breath, hold it and push

(perform extended Valsalva maneuver) so that abdominal muscules contract and help to expell the fetus. This increase in intra-abdominal pressure aids in fetal descent through the birth canal and this is the

indispensable condition of deliveryThe second stage of labor shouldn’t last longer than

two hours !!

The position of the patient for delivery most preferred by physicians is the dorsal lithotomy position (on the patient’s back). This allows the

physician to have better control of the delivery and facilitates subsequent surgical repair after delivery

In every succesive contraction, the maternal force correlated with uterine contractions cause more of

the fetal scalp to be visiable at the introitus.

In this moment: at the top of the contraction,

andafter local injection of anesthetic substance

(1% xylocaine)episiotomy (an incision of the perineum) is

performed (in our Clinic mediolateral)

- obligatory in primiparas - in some cases in multiparas

The main role of episiotomy is to enlarge the vaginal outlet and to facility delivery (especially

indicated in cases of instrumental delivery)

The episiotomy serves several purposes:

• it is a straight, clean surgical incision, not ragged laceration which otherwise is likely to occur

• it spares the baby’s head from perineal resistance

• it shortens the duration of the second stage of labor

Then the physician performs a modified Ritgen maneuver.

One hand is placed over the vertex while the other exerts pressure through the perineum onto the fetal chin.

The chin can then be delivered slowly, with control applied by the hand.

A sterile towel is used to avoid contamination of this hand by contact with the anus.

After delivery of the head the neck should be evaluated for the possible presence of a umbilical

cord, which should be reduced over the fetal head if possible. If the cord is tight, it may be doubly

clumped and cut.After delivery of the head , the shoulders descend

and rotate from transverse to the anteposterior diameter of the pelvis.

The attendant’s hands are placed on the occiput and vertex, applying gentle downword pressure, thus

delivering the anterior shoulder.The posterior shoulder is then delivered by upward

traction on the fetal head. The rest of the fetal body deliveries easily.

After delivery nasal and oral suction is performed.

It is especially important in case of presence meconium in amniotic fluid because of the possibility of MAS (meconium aspiration

syndrom).

After clumping the umbilical cord the newborn is attended to the neonatologist.

•Immediately after delivery of the infant, the uterus significantly decreases in size. This is the cause of separation of the placenta in the third stage of labor. The classic signs of placental separation are:- rise of the uterus in abdomen and its globular configuration- a gush of blood- lengthening of the umbilical cord

There are two modes of management in the third stage of labor:

1.Waiting for spontaneous extrusion of the placenta, even up to 30 minutes

2. Giving immediately after the delivery of the fetal head a bolus of Oxytocin for

making a strong contraction of the uterus

If spontaneous placental separation does not occur it is necessery to to remove the

placenta manually.

This is accomplished by passing a hand into the uterine cavity and using the palm of the

hand to separate the placenta from the uterine wall.

After delivery of the placenta the evaluation of its surface must be

performed.

If there are any lacks the revision of the uterine cavity by excochleation must be

done.

Then, inspection of the birth canal should be accomplished. It includes control of:

- lacerations of the introitus, vulvar area and periurethral area- lacerations of vagina and extensions of the episiotomy- lacerations of the cervix

Repair of these lacerations and the episiotomy is accomplished with an absorbable suture in local block.

Classification of perineum rupture:

• 1° - involves the vaginal mucosa or perineal skin, but not the underlying tissue

• 2° - involves the underlying subcutaneous tissue, but not the rectal sphincter or rectal mucosa

• 3° - extends through the rectal sphincter but not into the rectal mucosa

• 4° - extends into the rectal mucosa

Fourh stage of labor

For the first (especially two) hours aftere delivery there is the graetest risk of postpartum complications.

Postpartum uterine hemorrhage occurs in 1% of deliveries. It is more likely to occur in cases of:

- rapid labor

- protracted labor- uterine enlargement (large fetus, polihydramnios,

gemelli)

- prolonged use of betamimetic agent

In the fourth stage of labor the uterine palpation by abdominal wall must be

repeated in frequent intervals to accertain uterine tone.

The amount of blood loss must be observed.

It is also necessary to observe the pulse

and blood pressure.