Section 7 Labor

Physiology of labor PHYSIOLOGY OF LABOR PROLOGUE Regulated labor par parturition general contemporaneous theories discrible labor initiation Functional loss of pregnacy maintence factors Synthesis of factors that induce parturition Signal for parturition commencement → Labor = series of biochemical changes in uterus and cervix MARTERNAL AND FETAL COMPARTEMENTS Uterus - Compose myometrial layer of uterus - Smooth muscle shortening > striated muscle cell; - Contract of MULTIPLE direction Decidua = stromal cells and maternal immun cell → maintain pregnacy Function of cervix during pregnancy - Maintaince of barrier function to protect reproductive tract by infection - Maintaince of cervical competences dispite greater gravitational force of fetus grows - Orchestraition of extracellular marrxing → allow progressively greater issue compliance Placenta During labor PGDH (prostaglandin dehydrogenase) in chorion decline → membrane rupture and uterine contractility Amion - Virtullay all of fetal membrane - Highly resistant to penetration of leucocytes, micoorganism and neoplastic cell Chorion - Provides immunological acceptance - Enriched inactive enzyme: uterotonins, which stimulate contraction Aureus Physiology of labor SEX STEROID HORMONE ROLE All species studies: administration of mifepristoone or onapristone, an antagonistreceptor of progesterone → some or all key features parturition - Cervical ripening - Greater cervical distensibility - ↑ sensitivity to uterontonins Estrogen - Aids processes: uterine activation and cervical ripening - Both progesterone and estrogen binding same nuclear receptor o ERα and ERβ are isoform of PR-A and PR-B: differing transcripts of single gene PROSTAGLANDING ROLE - Prostaglanding promient role in o Myometrial contractility o Relaxing o Inflamtion - Interace of different G-protein coupledd receptor - The NSAIDs used to analesgic during pregnacy but they have adverse fetal effect (Loudon 2003; Olson 2003, 2007) PG during labor: PGE2; PGF2α; PGI2 - PG regulate events leading parturition PHASE 1: UTERINE QUIESCENCE AND CERVICAL SOFTENING Phase of parturition - Prelude to it - Prepation for it Aureus Physiology of labor - Process itself - Recovery Clinical stages of labor; 1st, 2nd, 3rd stages is in phase process itself Phase - Begining BEFORE implantation: 95% pregnacy o Uterine smooth muscle tranqulity → maintance cervical structural integrity Braxton Hicks contraction = false labor: contraction of myometrial but not cause cervical diliation Quiescence of phase froms Actions of estrogen and progesterone via intracellular receptors Myometrial-cell plasma membrane receptor-mediated increase in cAMP Generation cGMP Aureus Physiology of labor 4 Other systeme regulate par ion channels Myometrial relaxtion and contraction The Balance of relaxtion and contraction controlled by steroid and peptide hormone, quiescence is achived in part by - ↓ intracellular crosstalke and ↓ Ca2+ intracellular - Ion-channel regluation of cell membrane potential - Activation of uterine endoplasmic reticulum stress - Uterotonin degradation Contractility - Enhenced interations between actin and myosin - Heightened excitability of individual myometrial cells - Promotion of intracellular crosstalk Actin - Myosin interaction A Uterine relaxtion: ↑ cAMP Aureus Physiology of labor B Uterine contraction Regulation of membrane potentials - Maintance of hyperpolarized membrane o BKCa: large conductance voltage Myometrial gap junction - Each connexon = connexins subunits - Pair of connexon → coupled for cell exchange of small molecules - Progesterone matains uterine quiescence by lowers various of needed protein for contractility: CAPs (contraction-associated proteins: oxytocin receptors, PGF receptor, connexin-43) Endoplasmic Reticulum stress response G-Protein-coupled receptors - LH-hCG receptors: shared same G-protein Decidua - Ensure uterine quiescence: synthesis of decidua prostaglandins, PGF2α is suppressed Cervical Softening - Cervical softening results from o Increased vascularity o Cellular hypertrophy o Hpyerplasia o Slow, progressive compositional structural changes in extracellular matrix PHASE 2: PREPATION FOR LABOR → uterine awakening or activation Progesterone Withdrawal Mechanism - Inactivation by refractory of progessterone by myometrium and cervix Myometrial Changes - Change from expression protein control uterine quiescence to contractionassociated protein (CAPs) → responsive with uterotonins - Abdominal changes o Lower segment of myometrium differ froms upper uterine segment Oxytocin receptors - UNCLEAR: role in early phase? Or sole in expulsive phase of labor Aureus Physiology of labor - Progesterone and E2 → regulate oxytocin receptor o E2: raises myometrial oxytocin receptor concentrations o Progesterone: enhance oxytocin receptor degradations Cervical Ripening - Transition to softening → ripening: weeks to days before labor o Glycosaminoglycans o Proteoglycans Cervixcal connective tissue Cervix connective tissue - Collagen: tive I, III, IV High turnover during pregnacy GAGs - Hyaluronan increase viscoelasticity, hydrattion and matrix disorganization Inflammaotry Changes - When labor is underway → activation of neutrophils, proinflammatory M1 marcophages, tissue repair M2 marcophages → postpartum cervical remodeling and repair Induction of Cervical Ripeing - Key: PGE2 and PGF2α Endocervical Epithelia - Cnal: muscus secreting columnar and stratified squamous epithelia → form mucosal barrier and tight junctional barrier Feal Contribution to parturition Uterine Stretch Fetal endocrine cascades Aureus Physiology of labor - Late gestation: CRH of placenta stimulates fetal adrenal production DHEA-S and cortisol - Later: CRH → adrenal steroid hormone production - Fetal stress → increased CRH??? Fetal lung Surfactant and Platelet - Activation Factor - Surfactant protein A (SP-A) inhibits PG2α, and decreased in amnionic fluid at term - Fetal - maternal signaling for parturition Fetal - Membrane Senescence PHASE LABOR First stage: clinical onset of labor Uterine Labor contraction - Uterine smooth muscle during labor: Painful o Hypoxia of contracted myometrium → ↑ a lactic → same mechanism of angina pectoris o Compression of nerve ganglia in the cervix and lower uterus by contracted interlocking muscle bundels o Cervical stretching and during dilation o Stretching of the peritoneum overlying the fundus - Involuntary - Most part: independent of extrauterine control - Interval approximately 10 mins An < mins in nd stages - Unremitting contraction → cause fetal hypoxemia - Active phases: 30-90seconds; averages mins Dinstinct Lower and upper Uterine Segments Aureus Physiology of labor - Upper: contraction - Lower: softer, distend, more passive Changes in uterine shape: Fetal axis pressure → smaller horizontal diameter serves; then, lengthening of the uterus → lower segment and cervix → flexible Ancillary Forces : contraction of abdominal muscles simultaneously with respiratiory efforts with the glottis closed ~ pushing In 1st stages pushing is not nessesary because it harmful to fetal Cervical Changes: - Cervical effacement: shortening of cervical canal from aproximately cm to circular orifices Aureus Physiology of labor A: before labor: primigravid cervix: long and undilated; multipara: dilation of internal and external os B: Effacement begins, less happened in primigravid C: Completed effacement, primigravid: dilation is minimal; 1st stages end when cervical dilation is complete Aureus Physiology of labor 10 Second Stage: Fetal Descent Pelvic floor changes 1st stages of labor: stretching levator ani muscle fibers Third stage: delivery of placenta and membranes Begins immediately after fetal delivery and involes separation and expulsion of placenta and membranes Sudden diminution in uterine size is inevitables Completion of third stages is also accomplished by alternately compressing and elevating fundus Shcultze mechanism??: of placental expulsion, blood from the placental site pours into the membrane sac and does not escape externally until after extrusion of the placenta Duncan mechanism: the placenta separates first at the periphery and blood collects between the membranes and the uterine wall and escapes from the vagina UTEROTONINS IN PARTURITION PHASE Oxytocin - In Phase 2: number of myometrial oxytocin receptor grows appreciably → greater responsiveness contractile to oxytocin 10 Aureus Physiology of labor 11 - In phase 3: firm and persistent uterine contractions are essential to prevent postpartum hemorrhage Prostaglandins - Critical role in phase because of o Level of PG and its metabolite rise spike o Receptors for PGE2 and PGF2α expressed in uterus and cervix o Use of PG, any route → abortion or labor at all gestional ages Endothelin-1 - Endothelin is family of 21-amino-acid peptides powerfully induce myometrial contraction Angiotensin II - AT1 and AT2: o Nonpregnant: AT2 is dominant; buts AT1 preferently expressed in graviddas - Evokes contractions PHASE 4: THE PUERPERIUM - An hour after delivery, myometrium remains persistently contracted → prevent hemorrhage - Early puerperiumL lactogenisis and milk let down begin mammary glands - Ovulation happens with in 4-6 weeks after birth → tái khám vào thời điểm 11 Aureus Normal Labor 12 Figure A vertex; B sinciput C brow; D: face presentation o Complete o Footling presentation Fetal attitude - Rule: fetus form an ovoid mass tha correspond roughly to the shape of the uterine vavity: o Convex back o Head flex sharply: chin contact with the chest o Thighs flexed over the abdomen, leg bent at knees - Abnormal: fetal head extend → face presentation Fetal position - Chosen portion of fetal presenting in left of right side of birth canal o LO and RO (left occiput and right occiput) o LM and RM (left mental and right mental) o LS and RS (left sacral and right sacral) - The chosen portion presenting with maternal pelvis o Anterior (A) o Transverse (T) o Posterior (P) - Each presentation → varieties Figure A LOA; B LOP Normal Labor Figure A ROP ; B ROT 13 Normal Labor 14 Figure ROA - About 2/3 vertex presentations is LOP; 1/3 Right Diagnosis Leopold Maneuvers Leopold 1: identify fetal lie Breech is large, nodular mass Head: rounder, more mobile, harder Back is hard; other is numerous small, irregular, mobile part Thumb and fingers gasp the lower portions just above symphysis pubis, identify lie Determine degree of descent - With obese woman → palpations and actual birth weights often poorly Vaginal examination - Before labor, vaginal examination to diagnosis of lie and presentation is limited, when the fetus descent, and presenting part touchable through cervix - Differention of face and breech throught palpation the face and perineum - Routine vaginal examination: movements o Insert into vagina and found presenting part → differentiate: vertex, face and breech o If vertex: fingers are directed posteriorly and swept forward over fetal head and the maternal symphysis o Differentiate fontanel o Which part is descent Normal Labor Identify sagital suture Differentiating th fontanels Sonography and Radiography - During 2nd stage: sonography is more accurate Occiput Anterior Presentation Cardinal movements of labor Engagement This is mechanism of biparietal diameter through pelvic inlet Such lateral deflection to a more anterior or posterior position in the pelvis is called asynclitism If the sagittal suture approaches the sacral promontory, more of the anterior parietal bone presents itself to the examining fingers, and the condition is called anterior asynclitism If, however, the sagittal suture lies close to the symphysis, more of the posterior parietal bone will present, and the condition is called posterior asynclitism With extreme posterior asynclitism, the posterior ear may be easily palpated Descent - Nulliparas: engagement take place before the onset of labor - Multiparas: descent with engagement - driving forces o Pressure of the amnionic fluid 15 Normal Labor 16 o Direct pressure of the fundus upon the breech with contraction o Bearing-down effort of marternal abdominal muscles o Extension and straightening of the fetal body Flexion - Head meets resistance → flex Internal rotation - Essential for completion of labor, except the fetus is unusually small - Usually occiput rotates anteriorly toward the symphysis pubis Less, rotates tho the hollow of the sacrum - Head rotates after one or two contraction; and - In multiparas head rotates after three – five contractions Extension - Head to pelvic floor o Exerted by the uterus more posteriorly o Resistant of pelvic floor and the symphysis more anteriorly (fig 2.14) - Head: occuput → bregma → forehead → nose → mouth → chin External Rotation - Rotation to make shoulder get through Expulsion - The anterior shoulder appears under the symphysis pubis → posterior shoulder - These other partes quickly passes Normal Labor 17 Occiput Posterior Presentation - 20% is OP and ROP > LOP - In rotate OP rotate through 135 degrees Fetal Head Shape Change - Vertex presentation, labor forces alter fetal head shape Figure Caput succedaneum - Molding: changes in bony fetal head shape By external compressive forces NORMAL LABOR CHARACTERISTICS ... parturition Fetal - Membrane Senescence PHASE LABOR First stage: clinical onset of labor Uterine Labor contraction - Uterine smooth muscle during labor: Painful o Hypoxia of contracted myometrium... quickly passes Normal Labor 17 Occiput Posterior Presentation - 20% is OP and ROP > LOP - In rotate OP rotate through 135 degrees Fetal Head Shape Change - Vertex presentation, labor forces alter... segment Oxytocin receptors - UNCLEAR: role in early phase? Or sole in expulsive phase of labor Aureus Physiology of labor - Progesterone and E2 → regulate oxytocin receptor o E2: raises myometrial oxytocin