Normal labor and delivery • Definition of labor • Causes of onset of labor • Changes before labor (premonitory symptoms) • True labor • Essential factors of labor • Stages of labor • Clinical course and management of stages
Definition (1) Labor and delivery are the culmination of approximately 280days of preparation. Labor is the process by which the viable products ofconception (fetus, placenta, cord and membrane ) are expelled from the uterus. (whole process, series of events ,viable fetus) It is defined as the progress effacement and dilation of the cervix, resulting from rhythmic contraction of the uterine musculature. preterm labor—prior to 37 completed weeks
Definition (2) The term delivery refers only to the actual birth of the infant at the end of the second stage of labor. it is the expulsion or extraction of a viable fetus out of the womb. it is not synonymous with labor,delivery can take place without labor as in elective C.S. Delivery may be vaginal either spontaneous or aided or it may be abdominal.
Definition (3) • Normal labor (eutocia) : labor is called normal if it fulfils the following criteria. 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.
Definition (4) • Abnormal labor (dystocia): any deviation from the definition of normal labor. • Date of onset of labor:it is very much unpredictable to foretell precisely the exact dete of onset of labor.it not only varies from case to case but even in different pregnancies of the same individual.
Causes of onset of labor (1) • uterine distension: over-stretching of the uterus may play some part in onset of labor. Stretching effect on the myometrium by the growing size of the fetus and amniotic liquor can explain the onset of labor at least in twins or hydramnios. However “optimal distension theory” fails to account for the otherwise causeless preterm labor. • Feto-placental contribution: unknown factors stimulates fetal pituitary prior to onset of labor increased release of ACTH stimulates fetal adrenals increased cortisol secretion accelerated production of estrogen and prostaglandins from the placenta.
Causes of onset of labor (2) • The probable modes of action of oestrogen are: --increase the release of oxytocin from maternal pituitary --promotes the synthesis of receptors for oxytocin in the myometrium and decidua. --accelerates lysosomal disintegration inside the decidual cells resulting in increased prostaglandin synthesis. --stimulates the synthesis of myometrial contractile protein ---increase the excitability of the myometrial cell membranes.
Causes of onset of labor (3) • Progesterone: increased fetal production of dehydroepiandrosterone sulphate and cortisol may inhibit the conversion of fetal pregnenolone to progesterone, altering the estrogen : progesterone ratio. The alteration in the estrogen:progesterone ratio rather than the fall in the absolute concentration of progesterone which is linked with prostaglandin synthesis.
Causes of onset of labor (4) • prostaglandins: the major sites of synthesis of prostaglandins are placenta,fetal membranes,decidual cells and myometrium. Synthesis is trigged by ---rise in estrogen level, altered estrogen-progesterone balance, mechanical stretching in late pregnancy, increase in oxytocin receptors specially in the decidua vera, infection, separation or rupture of the membranes. • Oxytocin:it is probable that myometrial contraction is more dependent on its own readiness to respond to oxytocin. oxytocin level reaches the maximum at the monent of the birth.
Causes of onset of labor (5) • Nervous factors: labor may also be initiated through nerve pathways.
Premonitory symptoms (1) The premonitory stages may begin 2-3 weeks before the onset of true labor in primigravidae and a few days before in multiparae. The symptoms are inconsistent and may consist of the following: false labor (false pain) lightening blood show cervical changes
Premonitory symptoms (2) • False labor It usually appears prior to the onset of true labor pain, by one or two weeks in primigravidae and by a few days in multiparae. The woman feels pain and discomfort in the abdomen and these are mistaken for labor pain.
Premonitory symptoms (3) These Braxton-Hicks contractions cause the patient’s discomfort, it occur throughout pregnancy, late in pregnancy they become stronger and more frequent. But these contractions are not associated with progressive dilation of the cervix, and therefore do not fit the definition of labor. It is irregular and ineffective. It is not only a distressing feature to the woman but also annoying to the relatives.
Premonitory symptoms (4) • False pain has the following features: 1.discomfort is characterized as over the lower abdomen and groin areas 2.without effect on dilation of the cervix (not associated with progressive dilation ) 3.typically shorter in duration 4.less intense 5.relieved by administration of a sedative or ambulation
Premonitory symptoms (5) • Lightening Few weeks prior to the onset of labor specially in primigravdae, the presenting part sinks into the pelvis. The patient reports the sensation that the baby has gotten less heavy, the result of the fetal head descending into the pelvis. The patient often notice that the lower abdomen is more prominent and the upper abdomen is flatter, and there may be more frequent urination as the bladder is compressed by the fetal head.
Premonitory symptoms (6) This descending diminishes the fundal height and hence minimises the pressure on the diaphragm. This makes the woman more comfortable and has an easier time breathing. It is a welcome sign, as it rules out cephalopelvic disproportion and other conditions preventing the head from entering the pelvic inlet.
Premonitory symptoms (7) • Blood 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. This bloody show results as the cervix begins thinning out with the concomitant extrusion of mucus from the endocervical glands. Patients often report the passage of blood-tinged mucus late in pregnancy.
Premonitory symptoms (8) Cervical changes: several days prior to the onset of labor the cervix becomes ripe. A ripe cervix is soft, less than 1.3cm in length, admits a finger easily and is dilatable. Cervical effacement is common before the onset of true labor.
Ture labor or in labor • Painful uterine contractions • Increasingly intense and frequent • Is associated with progressive cervical effacement and dilation • Regular contraction occur every 5 minutes, duration lasts more than 30 seconds
False labor and true labor 1.discomfort is characterized as over the lower abdomen and groin areas 2.without effect on dilation of the cervix (not associated with progressive dilation ) 3.typically shorter in duration 4.less intense 5.relieved by administration of a sedative or ambulation 1.over the uterine fundus,with radiation of discomfort to the low back and low abdomen. 2. Associated with effacement and dilation 3. Increasingly intense and frequent 4. Regular and effective
Essential factors of labor(1) The progress and final outcome of labor are influenced by 4 factors: 1) the labor force 2) the passage (the bony and soft tissues of the maternal pelvis) 3) the passenger (fetus) 4) the psyche. Abnormalities of any of these components, singly or in combination, may result in dystocia.
Essential factors of labor(2) Uterine contraction. Labor force Abdominal muscle. Levator ani muscle Bony canal (pelvis) (no change) Birth canal vulvar, vagina, cervix, Lower uterine segment Fetal position Fetus Fetal size Psychic factors. A high level of anxiety during pregnancy has been associated with decreased uterine activity and with longer and dysfunctional labor.
Essential factors of labor(3) LABOR FORCE 1) Uterine contraction. It is the major force through the whole course of labor. It includes contraction and retraction. There are three effective features. Rhythmy and Intermittent Dominance and pacemaker Retraction.
Essential factors of labor(4) LABOR FORCE-uterine contraction (1) Dominance and pacemaker Uterine contraction in labor (patterns of contraction) there is good synchronisation of the contraction waves of both halves of the uterus. The pacemaker of uterine contractions is probably situated in the region of the cornu from where waves of contraction spread downwards.
Essential factors of labor(6)LABOR FORCE • Electrical traces of the pattern of uterine contraction show that in normal labor each contraction wave starts near one or other uterine cornu. The contraction spreads as a wave in the myometrium, taking 10-30 seconds to spread over the whole uterus.
Essential factors of labor(7)LABOR FORCE Dominance :The upper segment contracts more strongly than the lower part, and the duration is longer than in the lower segment, this dominance of the upper segment leads to the stretching and thinning of the lower segment and to dilation of the cervix.
Essential factors of labor(8)LABOR FORCE • (2) The contractions are regular and rhymic.
Essential factors of labor(9)LABOR FORCE After contractions there is a intermittent. As labor progress, the intensity increase, frequency increase, contractile duration prolong and intermittent shorten gradually, by the end of the first stage of labor the contraction may come every 1 to 2 minutes and may last as longas a minute.
Essential factors of labor(10)LABOR FORCE • Intermittent : The intermittent nature of the contractions is of great importance to both the fetus and the mother. During a contraction the circulation to the placental bed through the uterine wall is stopped; if the uterus contracted continuously the fetus would die from lack of oxygen. The intermittent allow the placental circulation to be re-established and give the mother time to recover from the fatigue effect of the contraction. The uterus is a large muscle and contractions use up a lot of energy, if continued too long this would produce maternal exhaustion.
Essential factors of laborLABOR FORCE uterine contraction include three parts: intensity duration frequency
Essential factors of laborLABOR FORCE • Intensity of contraction: it 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. During the first stage intrauterine cavity pressure is raised to 40-50mmHg and during second stage it is raised about to 100-120 mmHg. Frequency: in the early stage of labor, the contraction come at intervals of 10-15 min. The intervals gradually shorten with advancement of labor until in the second stage, when it comes every one or two minutes.
Essential factors of laborLABOR FORCE Duration: in the first stage, the contraction lasts for about 30-40 seconds initially but gradually increases in duration with the progress of labor. Thus in the second stage, the contractions last longer than in the first stage.
Essential factors of labor(11)LABOR FORCE-- retraction • Uterine contraction and retraction is throughout the full labor. The uterus not only contract but also retract. The dilation of the cervix, descent of presenting part and progress of labor depend on the uterine contraction and retraction.
Essential factors of labor(12)LABOR FORCE-- retraction • Retraction: retraction is a phenomenon of the uterus in labor in which the muscle fibres are permanently shortened, it is different from the contraction. Retraction is specially a property of upper uterine segment. Contraction is a temporary reduction in length of the fibres, which attain their full length after the contraction passes off. In contrast, retraction results in permanent shortening and the fibres are shortened once and for all. When the active contraction passes off the fibres lengthen again, but not to their original length.
Essential factors of labor(14)LABOR FORCE-- retraction If contraction was followed by complete relaxation no progress would be made, in retraction some of the shortening of the fibres is maintained. So the uterine cavity becomes progressively smaller with each contraction. The net effect of retraction in normal labor are: -- essential property in the formation of lower segment and dilation and taking up of the cervix -- to maintain the advancement of the presenting part made by the uterine contraction and to help in ultimate expulsion of the fetus -- to reduce the surface area of the uterus favouring separation of placenta
Essential factors of labor(15)LABOR FORCE • Abdomenal muscle and diaphram. • In second stage,delivery of the fetus is accomplished by the downward thrust offered by uterine contractions supplemented by voluntary contraction of abdominal muscles against the resistance offered by bony and soft tissues of the birth canal. • Help fetus and placenta delivery in the second stage and third stage.
Essential factors of labor(16)LABOR FORCE • the expulsive force of uterine contraction is added by voluntary contraction of the abdominal muscles called “bearing down” efforts. • Pelvic floor (levator ani muscle.) Help fetus internal rotation
Essential factors of laborbirth canal The bony canal The bony canal means true pelvis, its size and shape is relation with delivery closely. There three plane. Pelvic inlet plane. The true conjugate describe the anteroposterior dimension of the inlet, it is average 11cm. The transverse diameter of the inlet is average 13cm. An oblique diameter is average 12.75cm.
Essential factors of laborbirth canal Pelvic midplane. it is the smallest plane of the pelvic canal. Its anteroposterior diameter is average 11.5cm. its transverse diameter between the ischial spines( interspinous diameter) is average 10cm The plane of least dimensions is an important obstetric plane because shortening of its diameters frequently is associated with obstructed labor.
Essential factors of laborbirth canal pelvic outlet plane. The plane of the pelvic outlet is actually two triangular planes at different inclinations that share the same base. The transverse diameter, between the inner margins of the ischial tuberosites, average 9cm. • pelvic axis and inclination of pelvis
Essential factors of laborbirth canalThe soft birth canal The formation of lower segment. • Before labor begins, the uterine body appears to be a single unit. However, uterine contractions soon cause it to differentiate into visibly different upper and lower segments. • The upper segment is actively contractile, thick, and powerful. The lower segment is passive, thin, and distensible. • The physiologic retraction ring separates the two segments.
Essential factors of laborbirth canal This powerful segment draws the weaker, thinner and more passive lower segment up over its contents, and in so doing pulls up and then dilates the cervix. The wall of the upper segment becomes progressively thicker with progressive thinning of the lower segment. This is pronounced in late first stage, specially after rupture of the membranes and attains its maximum in second stage. A distinct ridge is produced at the junction of the two segments, called physiological retracting ring.
Essential factors of laborbirth canal • The change of cervix After cervical effacement ,dilation of cervix begins in primigravidae. But in multiparae the effacement and dilation occur together.