NORMAL LABOUR

🔆DEFINITION🔆
A mture at term fetus presenting by vertex is delivered spontaneously through birth canal within 24 h without interference except episiotomy and without fetal or maternal complications with effective uterine contraction.
🔆CAUSES OF ONSET OF LABOUR🔆
It is unknown but the following  theories👇🏻.
⚜HORMONAL THEORIES:
(1)🔅-Oestrogen theory:
During pregnancy, most of the oestrogens are present in a binding form. During the last trimester, more free oestrogen appears increasing the excitability of the myometrium and prostaglandins synthesis.
(2)🔅-Progesterone withdrawal theory:
Before labour, there is a drop in progesterone synthesis leading to predominance of the excitatory action of oestrogens.
(3)🔅-Prostaglandins theory:
Prostaglandins E2 and F2α are powerful stimulators of uterine muscle activity. PGF2α was found to be increased in maternal and foetal blood as well as the amniotic fluid late in pregnancy and during labour.
(4)🔅-Oxytocin theory:
Although oxytocin is a powerful stimulator of uterine contraction, its natural role in onset of labour is doubtful. The secretion of oxytocinase enzyme from the placenta is decreased near term due to placental ischaemia leading to predominance of oxytocin’s action oxytocin receptores on uterine muscel increase .
(5)🔅-Foetal cortisol theory:
Increased cortisol production from the foetal adrenal gland before labour may influence its onset by increasing oestrogen production from the placenta.
⚜MECHANICAL THEORYS:
(1)🔅-Uterine distension theory:
symple as Like any hollow organ in the body, when the uterus in distended to a certain limit, it starts to contract to evacuate its contents.
(2)🔅-Stretch of the lower uterine segment:
by the presenting part near term lead to myogenic reflex to uterine body muscle to increase contact . also neurogenic reflex to increase secreation of oxytocin hormone.
🔆CLINICAL PICTURES OF
BRE-LABOUR STAGE🔆
(1)🔅-True labour pain with utrine contraction:
at term 👉🏻 they became increasing strength and frequency. Late in pregnancythey become stronger (progressive) and more frequent associated with bag of forewaters and dilation of cervix , increase with enama. not relieve by sedative radiated to the back.
but 👉🏻the braxton Hickscontractions (false labor) are not associated with dilation of thecervix, and do not fit the definition of labor.
are typically shorter in duration and less intense and frequency thantrue labor contractions, with the discomfort being characterized as over the lower abdomen and groin areas. resolve with
ambulation, hydration, or analgesia.
(2)🔅- Shelfing:It is falling forwards of the uterine fundus making the upper abdomen looks like a shelf
during standing position. This is due to engagement and the head became perpendicular to the pelvic inlet.
(3)🔅- Lightening:It is the relief of chest symptoms as dyspnoea andpalpitation due to descent in the fundal level after engagement of the head and shelfing of the
uterus. and patient starting combine from Pelvic pressure symptoms With engagement of the presenting part as Frequency of micturition. rectal tenesmus. difficulty in walking. Increased vaginal
discharge.False labour pain.
(4)🔅- The show:It is an expelled cervical mucus plug stianed with blood from ruptured small vessels as a
result of separation of the membranes from the lower uterine segment and laceration of cervical mucosa . Labour is usually startsseveral hours to few days after show.
(5)🔅- Dilatation of the cervix: due to effective contraction and retraction of uterine muscle with true labour pain.
(6)🔅- Formation the bag of forewaters:
It bulges of amniotic membranes through diluted cervix after separation from lower uterine segment and becomes tense during contraction.
🔆🔱STAGES OF LABOR🔱🔆
⚜- It is divided into
four functional stages :
🔅(1) • The first stage of labor is the interval between the onsetof true labor pain into full cervical dilation (10 cm 5 fingers).
🔅(2) • The second stage of labor from complete cervical dilation to explusion  of the infant for 0.5--1h.
🔅(3) • The third stage of labor begins immediately after
delivery of the infant and ends with the delivery of the
placenta and membrane and cord for 0,25 -- 0,5 h
🔅(4) • The fourth stage of labor is defined as the immediatepostpartum period of approximately 24 hours after delivery of the placenta, during which time the patient undergoes significant physiologic adjustment (recovery).
🔆MECHANISM OF FRIST STAGE OF LABOUR🔆
In primigravida the cervix strat dilatation from above downward. strat dilated of internal Os then cervical canal and finally the external Os. but in multipara all diluted and effaced at the same time.
⚜The first stageis further divided into two phases:
🔅(1)-The latentphase of labor encompasses cervical effacement and slow early dilation  3-4 cm for 4h in mutipar 8h in primigraveda.
🔅(2)- the active phase of labor, duringwhich more rapid cervical dilation occurs, usually  to 9cm for 2h in multipara 6h in primigraveda.
🔆MECHANISM OF SECOND STAGE OF LABOR 🔆
The mechanisms of labor also known as the cardinal
movements of labor  refer to the changes of the
position of the fetus as it passes through the birth canal.
(A)⚜-Delivery of the head:
by following cardinal movement 👇🏻.
(1)- Descent
(2)- Engagement..
(3)- Exaggerated flexion.
(4)- Internal rotation.
(5)- Extension.
(6)- External rotation (restitution).
(7)- Expulsion.
⚜The following 👇🏻 more details about cadinal movement during labour.
🔅-Descent: It is continuous throughout labour particularly during the second stage and caused by Uterine contractions and retractions and contraction of the diaphragm and abdominal muscles.
🔅-Engagement. it is descent of the biparietal diameter of the head below the plane of the pelvic inlet( pelvic brime) , detecte clinically by   palpation of the presenting part PV belowthe level of ischial spines (zero station). commonly occurs in last two weeks in primegraveda whereas in multigraveda it more commonly happens at the onset of activelabor.
🔅- Exaggerated flexion: As the atlanto -occipital joint is nearer to the occiput than the sinciput. occurs when it meets the pelvic floor results in. the suboccipito -bregmatic diameter (9.5 cm) passes throughthe birth canal instead of the suboccipito-frontal diameter (10cm). The part of the foetal headapplied to the maternal passages is like a ball with equal longitudinal and transverse diameters asthe suboccipito -bregmatic = biparietal = 9.5 cm.theocciput will meet the pelvic floor.
🔅- Internal rotation: The rule is that the part of foetus meets the pelvic floor first will rotate anteriorly.
So that its movement is in the direction of levator ani muscles of the pelvic floor
i.e. downwards, forwards and inwards.In normal labour , the occiput which meets the pelvic floor
first rotates anteriorly 1/8 circle.
🔅- Extension: The suboccipital region lies under the symphysis then by head extension the vertex,
forehead and face come out successively.The head is acted upon by the uterine
contractions acting downwards and forwards.the pelvic floor resistance acting upwards andforwards so the net result is forward direction.
🔅- Restitution: After delivery, the head rotates 1/8 of a circle in the opposite direction of internalrotation to undo the twist produced by it.
(B)⚜-Delivery of the shoulder and body:
The anterior shoulder hinges below the symphysis pubis and with continuous descent the posterior shoulder is delivered first by lateral flexion of the spines followed by anterior shoulder then remain of the body.
🔆MECHANISM OF THIRD STAGE OF LABOUR🔆
After delivery of the foetus , the uterus continues to contract and retract. As the placenta isinelastic, it starts to separate by one of the following mechanisms:
(1)🔅-Schultze’s mechanism (80%):
The central area of the placenta separates first and placenta is delivered like an inverted umbrella. so the foetal surface appears first followed by the membranes containing small retroplacentalclot .There is less blood loss and less liability for retention of fragments.
(2)🔅-Duncan’s mechanism (20%):
The lower edge of the placenta separates first and placenta is delivered side ways .There is more
liability of bleeding and retained fragments.
⚜The 3rd stage is composed of
3 phases:
1-Placental separation.
2-Placental descent.
3-Placental expulsion.
⚜Signs of third stage:
1-gush of blood.
2- increase the length of cord.
3-firm uterus due to bainless contraction.
4-uterus rise anteriorly.
The next lecture is👇🏻
-How to manage .

د/سامي عارف عبدالجليل الشميري