series of events that take place in the genital organs in an effort to expel the viable fetus out of the uterus through the vagina in to the outer world.
Definition of delivery:-
Is the expulsion or extraction of a viable fetus out of the uterus .
Labour is normal when it is
Spontaneous in onset
Without undue prolongation
With no maternal complications or
- Any deviation from this definition is abnormal
On set of labour
Based on naegel’s formula labour starts approximately as follow.
In the expected date of delivery in 4% of cases
One week on either side in 50% of cases
Two weeks earlier and one week later on 80% of cases
At 42 weeks in 10% of cases
At 43 weeks plus in 4% of cases
Causes of the onset of labour
Unknown the following theories were postulated
Optimal distension theory
When the uterus is distended to a certain limit, it starts to contract to evacuate its contents (multiple preg. Polyhydramnios)
2. feto- placental theory
- Due to unknown factors fetal pituitary is stimulated with increase release of ACTH that stimulate the
fetal adrenal to produce cortisol which act in the placenta to produce estrogen and prostaglandins.
3- estrogen theory:-
during the last trimester more free estrogen appears increasing the excitability of the myometrium and prostaglandin synthesis
Increase fetal production of dehydroepiandro-sterone sulphate with cortisol may inhibit the conversion of fetal pregnenolone to progesterone there by altering the estrogen progesterone ratio.
5- prostaglandins :-
- Attracted much attention in recent years produced by-placenta –membrane –decidual cells and myometrium
Synthesis is triggered by
Rise in estrogen level
Altered estrogen. Progesterone ratio
Mechanical stretching in later pregnancy
Infection or separation of membranes
↑ oxytocin receptors
6. Oxytocin theory:-
although oxytocin is a powerful stimulator of uterine contraction its natural role in onset of labour is doubtful .
Diagnosis of labour :-
Pre labour (premonitory stage :-
- May begins two to three weeks before the onset of true labour in PG. and few days before in multi gravida and may consist of the following .
1)Lightening :- A sense of relief from the upper abdominal pressure symptoms such as dyspnoea or dyspepsia due to sink of the presenting part into the true pelvis .
2.Pelvic pressure symptoms such as frequency of micturition due to engagement of the presenting part .
3.Cervical changes (ripening of the cervix) become soft , less than 1.3cm in length ,Admit tip of the finger and is dilatable .
4.Appearance of false pain .
Features of true labour are :-
Intermittened painful and regular .
Increase progressively in frequency, duration and intensity .
Felt in the abdomen and radiate to the back and thigh .
2)The show Expulsion of the cervical mucus plug mixed with blood –may occur few days before the onset of labour .
3) Progressive effacement and dilatation of the cervix .
4) Formation of the bag of forewater ,the lower pole of the fetal membranes become unsupported and tend to bulge through the cervical canal .
Stages of labour
Labour is divided into four stages:-
1- First stage of labour:-
It is the stage of cervical dilatation .
Starts with the onset of labour pain and ends with full dilatation of the cervix .
It takes about 12 hours in a Primipara, and 8hrs in a multipara .
It’s composed of two phases .
A) Latent phase:
Starts from the onset of labour and ends when the cervix is (2 to3 cm) dilated . It occurs because the thinning of the lower segment and cervix take a lot of uterine work before rapid dilatation can begin . It takes about (6 to 8 hrs) .
B) Active phase :-
It is the phase of rapid dilatation of the cervix from 3cm dilatation up to full dilatation it also take (6hrs) with a rate of cervical dilatation of (1.2cm/hour)in PG and (1.5cm/hour)in multigravida .
It has three components:-
i) Accelerated phase of dilatation from (2.5cmto4cm).
ii) Phase of maximum slope of (4to9cm) dilatation .
iii) Phase of deceleration of (9-10cm) dilatation .
Causes of cervical dilation:-
Contraction and retraction of uterine musculature (primary force)
- Normal uterine contraction occur with frequency of one every 2-3 minutes with at least 1min between contraction. With a duration of 40-70 seconds and an intensity of around 50 mmHg & a resting tone less than 15 mmHg
The contraction begins in two pace makers near the utrotubal junction –only one pace maker is operative in each contraction. It spread like a wave over the whole uterus- strong in the funds (fundal dominance) less strong in the mid zone and relatively in the lower segment.
Relaxation begins simultaneously in all areas of the uterus.
The force generated by each contraction is applied to the amniotic fluid and directly
Against the pole of the infant that occupies the upper segment therefore each time the muscle contracts the uterine cavity becomes smaller and the presenting part or the fore bag of water lying a head of it is pushed down ward in to the cervix this tends to force it to open or dilate .
A more potent factor in cervical dilatation however is the retraction of the upper segment. As this area of the uterus becomes shorter and thicker it pulls the lower segment and the dilating cervix upward around the presenting part at the same time the
uterus contracting directly against the infant tends to push it through the cervical opening .
Cervical dilatation in primigravida occurs from above down ward causing progressive shortening of the cervix.( effacement).
In multigravida effacement and dilatation occurs simultaneously.
2. Second stage of labour
It is the stage of expulsion of the fetus
Begins with full cervical dilatation and ends with delivery of the fetus
Its duration is about one hour in primigravida and ½ an hour in multigravida.
Delivery of the fetus is affected in addition to the uterine contraction( primary force) by voluntary contraction of the abdominal muscles with the diaphragm fixed after forced inspiration .
This will increase intra abdominal pressure (secondary force).
This secondary forces have no effect on cervical dilatation but they are of considerable importance in aiding the expulsion of the infant from the uterus and vagina after the cervix is completely dilated.
3- third stage of labour:- comprises the phase of placental separation its descent to the lower segment and finally its expulsion with the membrane. www.doctor.sd
It begins after delivery of the fetus and end with expulsion of the placenta and membrane.
Duration is about 10__20 minutes in both primigravide and multigravida.
Placental separation is due to marked uterine muscle retraction which reduces the surface area at the placental site to about its half but as the placenta is inelastic a shearing force in instituted bringing about its separation. the plane of separation runs through the deep spongy
Layer of the decidua basalis
There are two mechanism of placental separation.
1- central separation (Schultz) occur in 80% of cases- detachment of placenta from its uterine attachment starts at the centre.
2- marginal separation( Mathews –Duncan) occurs in 20% of cases. Separation starts at the margin as it is mostly un supported
After complete separation of the placenta it is delivered by effective uterine contraction and retraction and expelled out by either voluntary contraction of abdominal muscle (bearing down effort) or by manipulative procedures.
After placental delivery the uterine sinuses and arterioles are occluded by effective uterine contraction and retraction which is the principle mechanism of haemostasis, however thrombosis also occurs and is facilitated by the hypercoagulable status of pregnancy.
4-fourth stage of labour
Begins immediately after expulsion of the placenta and membranes and last for one hour.
Careful observation of the patient for signs of postpartum hemorrhage is essential.
Mechanism of normal labour:-
It refers to the series of changes in position and attitude which the fetus under goes during its passage through the birth canal
And it consist of the following.
Descent of the fetus is a continuous movement it is slow or insignificant in the first stage of labour but pronounced in the second stage. it is completed with the expulsion of the fetus. It is due to contraction and retraction of uterine muscle (primary force). Added in the second stage by bearing down efforts (secondary force).
As the head meet the resistance of the birth canal during descent full flexion is achieved to bring the shortest sub-occipito bregmatic diameter. Of the head(9.5cm).
Flexion is essential for descent since it reduces the shape and size of the plane of the advancing diameter of the head.
3- internal rotation
In the second stage of labour the forces propel the fetus progressively down the birth canal, when the head meets the resistance of the pelvic floor the occiput rotates forward to lie under the sub pubic arch with the sagittal suture in the antero-posterior diameter of the pelvic out let . This internal rotation of the head occurs because with a well flexed head the occiput is leading and meets the slopping gutter of the
Lavatores ani muscles which by their shape direct it anteriorly.
further advances of the head lead to its passage through the vulva by a process of extension. Once the occiput has escaped from under the symphysis pubis the head extends with the nape of neck pressed firmly against the public arch. The successive parts of the fetal head to born through the stretched vulval .out let are vertex , brow and face.
As soon as the head is completely born it resumes its natural position with regard to the shoulders by rotating 1/8 th of a circle in the direction opposite to that of internal rotation. The neck becomes untwisted and the head is restored to its natural relation to the shoulder.
6. External rotation
It is the movement of rotation of the head visible externally due to internal rotation of the shoulders it carries the head in a movement through 1/8 th of a circle in the same direction as restitution.
7- Birth of shoulders and trunk:-
- Further descent takes place the anterior shoulder escapes below the symphysis pubis and by lateral flexion of the spine the posterior shoulder sweeps over the perineum. Rest of the trunk is there expelled out
Management of normal labour
On admission a complete history must be taken
Antenatal record is reviewed to discover whether there have been any abnormalities during pregnancy
The women general condition is assessed her pulse-blood pressure and temperature are recorded
on abdominal examination the presentation and position of the fetus and the relation of the presenting part to the brim of the pelvis are determined
Abdominal examination will also show the frequency and strength of uterine contraction .
The location, rate and regularity of the fetal heart tones are also determined.
A vaginal examination will show the degree of cervical dilation, whether the membranes are intact or rupture and the
Position with station of the presenting part.
A urine specimen is examined for protein and glucose and a hemoglobin or haematocrit determination is made.
It’s routine use is unnecessary and has no particular benefit.
Usually given early in the first stage of labour to empty the rectum to prevents soiling of the perineum during the second stage.
Shaving or clipping of the vulval hair
Is not necessary
Awarm bath or shower is both hygienic and pleasant.
there is no need for the women to remain in bed during early labour. She is allowed to walk about and to sit. This attitude prevents venacaval compression and encourage descent of the presenting part.
The major risk to be avoided is aspiration of gastric contents, this only occurs in the context of general anesthesia.
Intake of solid food must be avoided, low fat, low residuce food and drink can be given.
If dehydration needs to be corrected normal saline should be infused.
The patient should be encouraged to empty her bladder frequently as full bladder often inhibits uterine contraction.
If the patient fails to pass urine specially in late first stage catheterization is to be done with strict aseptic precaution .
Relief of pain:-
Pethidine (100) mg intramuscularly can be given when the pains are well estabished. It.
should not be given if delivery is anticipated within two hours
Epidural analgesia is very effective & do not cause depression of fetal respiration
If epidural is not used towards the end of first stage a mixture of nitrous oxide & Oxygen (Entonox) may be started with the onset of each contraction.
One labour has become established all events during labour should be recorded on the partogram.
Cervical dilatation marked in centimeters at the time of admission to ward and at every subsequent examination(2 hourly)
Descent of head (in cm above or below the lschael spine).
Frequency, duration and strength of uterine contration in (10)min. each half an hour.
Fetal heart rate every ½ an hour.
Condition of liquor and time and manner of membranes rupture.
moulding of the fetal skull
Dosage of Oxytocin if used
Maternal status (BP- pulse- temp-urinalysis).
Medication (including epidural block if used
Management of the second stage:-
The transition from the first stage to the second stage is evidenced by the following features.
Appearance of bearing down efforts
Complete dilatation of the cervix on vaginal examination.
Principles of management are:-
1. To assist in the natural expulsion of the fetus slowly
2- to prevent perineal injuries
General measures :
FHR every 5 minutes
Maternal pulse and blood pressure every 15mins
If epidural block is not used to administer inhalation analgesia (entonox) to relieve pain during contraction
Vaginal examination to confirm the on set of the second stage – to detect cord prolapse and to know the position and station of the head
Nothing is given by mouth
Preparation for delivery:-
Bearing down efforts, bulging of the perineum and gaping of the anal opening during contraction signify that delivery is imminent so the patient should be shifted to the labour table
Position of the patient
Dorsal position is more widely preferred with the thighs flexed and separated . Some however prefer delivery in lateral or lithotomy position
Toileting the external genitalia and inner Side of the thighs with cotton swabs soaked in savlon . And the area is covered with sterile sheet. Keeping only the external genitalia uncovered
The delivery attendant should scrub put on sterile gown ,mask and gloves
To catheterize the bladder if it is full.
Conduction of the delivery
The patient is encourage to intensify the bearing down efforts during contractions.
When the scalp is visible for about 5cm diameter flexion of the head is maintained during contraction by pushing the occiput down wards and back wards by using thumb and index fingers of the left hand while pressing the perineum by the right palm with a sterile vulval pad. This process is repeated during subsequent
contraction until crowing of the head occurs (biparietal diameter stretches the vulval out let without any recession of the head even after the contractions is over).
When the perineum is fully stretched and threatens to tear specially in PG episiotomy is done at this stage after prior infiltration with 10/ml of 1% lignocaine.
Slow delivery of the head is accomplished by pushing the chin with sterile gauze .by covered fingers of the right hand placed over the anococcygeal region
While the left hand exerts pressure on the occiput. the forehead, nose, mouth and the chin are thus born successively over the stretched perineum by extension.
The mucus and blood in the mouth and pharynx should be wiped with sterile gauze or alternatively mechanical sucker may be used.
The neck is then palpated to exclude the presence of any loop of cord if it is found it should be slipped over the head or if it is sufficiently tight it is cut in between two pairs of kocher’s forceps.
Wait for uterine contractions to come and for the movements of restitution and external rotation of the head to occur, the anterior shoulder is born behind the symphysis. If there is delay the head is grasped by both hands and is gently drawn posteriorly until the anterior shoulder is released from under the pubis. by drawing the head in upward direction the posterior shoulder is delivered out of the perineum.
After delivery of the shoulders the fore fingers of each hand are inserted under the axillae and the trunk is delivered gently by lateral flexion.
Some delay in clamping and cutting the umbilical cord probably is beneficial to the infant. As much as a 75 to 100ml increase in fetal blood volume can be anticipated.
The infant is placed in a heated crib with its head slightly lower than its body. Its air passage should be cleared of Mucus by sucker before vigorous respiratory efforts are established.
Apgar rating at 1 minute an at 5 minute is to be recorded
A sterile cotton thread is applied to the cord 2.5cm away from the navel & the cord is divided with scissors about 1 cm beyond the ligature.
Defined as a planned surgical incision of the perineum made to increase the diameter of the vulval outlet during childbirth (perineotomy)
Types of episiotomy
1-midline:- the cut is made vertically from the fourchette down towards the anus.
Advantages of this incision are less blood loss, is easier to repair, the wound heals quicker, and less postpartum pain and dyspareunia. The major disadvantage it carries a higher risk to extend to involve the anal sphincter.
This incision starts in the midline of the fourchette and then directed outwards to avoid the anal sphincter
management of the third stage:
Two methods of management are currently in practice
- In this management the placental separation and its descent into the vagina are allowed to occur spontaneously. When the features of placental separation at its descent into
the lower segment are confirmed the patient is asked to bear down simultaneously with uterine contraction. The raised intra- abdominal pressure is often adequate to expel the placenta. If the patient fail to expel the placenta. controlled cord traction (Brandt- Andrews method) can be tried. The palmer surface of the fingers of the left hand is placed approximately at the junction of upper and lower uterine segment the body of the uterus is displaced upwards and backwards towards the umbilicus while by the right hand steady tension is given in
Downwards and backward direction until the placenta comes outside .
Signs of placental separation:-
1. A show of blood appears as the uterus contracts.
2. Lengthening of the cord
3. The fundus become globular in shape, rises above the umbilicus, become palatable.
2. Active management:-
Is associated with reduced blood loss.
I.V ergometrine or syntometrine (syntocinon 5 units +ergometrine 0.5mg) is given with delivery of the anterior shoulder.
The placenta is immediately delivered after delivery of the baby by controlled cord traction after insuring uterine contraction
As soon as the placenta passes through the introitus it is grasped between the hands and twisted around and round with gentle traction so that the membranes are stripped intact.
The placenta and the membranes should be examined following their expulsion
Vulva-vagina and perineum are inspected carefully for injuries and to be repaired if any. the episiotomy is sutured. The vagina is evacuated from blood clots . The area is cleaned and a dry sterile vulval pad is placed.
The maternal condition –pulse –blood pressure. Behavior of the uterus and any abnormal vaginal bleeding is to be watched at least for one hour after delivery (fourth stage of labour).
When fully satisfied that the general condition is good pulse and blood pressure are steady the uterus is well contracted and there is no abnormal vaginal bleeding the patient is sent to the ward.