9.Preterm Labor
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Transcript of 9.Preterm Labor
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Preterm LaboPreterm Laborr
General hospital of Tianjin medical university
Zhang Xuhong
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In USA:morbidity 10% Neonatal morbidity and mortality 50%-70%
In China:morbidity 5%-15%
Neonatal mortality 15%
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DefinitionDefinition
Preterm labor is defined as that occuring after 20 weeks and before 37 completed weeks of gestation.
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Etiology and risk Etiology and risk factorsfactorsEtiologic subtypes of pret
erm laborOther undiagnosed condi
tions and problemsHigh risk factors
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There are three etiologic sThere are three etiologic subtypes of preterm laborubtypes of preterm labor
Spontaneous preterm birthPreterm premature rupture of
the membranesInduction of labor for medical
indication: preeclamsia,cardiac disease
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Undiagnosed Undiagnosed conditionsconditions Placental originSilent infectionImmunologic etiologyUterine originCervical origin
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High risk factorsHigh risk factors Socioeconomic factors: race Medical and obstetric factors (1)Preterm birth occurred before (2)Second-trimester abortion and repeate
d spontaneous first-trimester abortions (3)Bleeding, urinary tract infection, uterin
e anomalies, polyhydramnios,multiple gestation…
(4)Bad nutritional status,stress and anxiety
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Clinical findingsClinical findings
Uterine contractions: regular contractions at frequent intervals,generally more than 2 in onehalf hour
Dilatation and effacement of cervix:2cm
Vaginal bleeding: evaluate for placenta previa and placenta abruption
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EvaluationEvaluation
Gestational age: 20-37;LMP and EDC
Fetal weight: biparietal diameter and lenth of thighbone
Presenting part:Fetal monitoring: NST( non-stres
s test
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Infection-cervical Infection-cervical pathwaypathway
Bacteria vaginosisVaginal-cervical infections and
cervical lengthFibronectin test (1)positive:22-24weeks, predict
preterm labor (2)negative:low risks
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DiagnosisDiagnosis The diagnosis of preterm labor occurring
between 20-37weeks is based on the following criteria in patients with ruptured or intact membranes
(1) Documented uterine contractions ( 4 per 20 minutes or 8 per 60 minutes)
(2) Documented cervical changes: cervical effacement of 80% or dilatation of 2cm or more
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ManagementManagement
Adequate hydration and bed restVaginal examnationCultureAntibiotic therapyLaboratory testsUltrosonic examinationTocolytic therapy
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Hydration and bed restHydration and bed restIf the patient represents preterm
labor, she can not go to work or do any house work. With adequate hydration(either oral or parental) and bed rest, uterine contractions cease in approximately 20% of patients.
If necessary, she should go to see doctors.
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Vaginal examinationVaginal examinationNo membrane rupture and no contrai
ndications.Ascertain cervical length and dilation.Ascertain the station and nature of th
e presenting part of the fetus.Monitor for uterine contractions, its p
resence, frequency and intensity.
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Cultures of vagina diachargeCultures of vagina diacharge
Main organisms in the etiology of preterm labor:
Group B streptococcus
Ureaplasma
Myoplasma
Gardnerella vaginalis
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Diagnosis of bacteria vaginosisDiagnosis of bacteria vaginosis
Vaginal PH> 4.5 (3.8- 4.4)Whiff test (+) : amine odor after additi
on of 10% potassium hydroxidePresence of clue cellsMilky dischargeThe diagnosis can be made by the presence
of three of four clinical signs.
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Antibiotic therapyAntibiotic therapy
Penicillin is the first chioceA 7-day course of ampicillin and/
or erythromycin( no allergy)Clindamycin or vacomycin( aller
gy)
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Laboratory testLaboratory test
Complete blood cell countRandom blood glucose leverSerum electrolytes lever(Ca2+, M
g2+)Urinalysis (protein, glucose, WB
C,RBC)Urine culture and sensitivity
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Utrasonic examinationUtrasonic examinationDetect document presentationAssess cervical lengthRule out fetus congenital malformati
onAssess fetal weight Uterine anomaly:
uterus bicornis (双角) uterus septus (纵隔)
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Uterine tocolytic therapyUterine tocolytic therapy
Uterine tocolytic agents
(1) Magnesium sulfate
(2) Nifedipine
(3) Prostoglandin synthetase inhibitors
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Magnesium sulfateMagnesium sulfate
The first choice of tocolytic therapyCompete with calcium ions for entry i
nto the cell at the time of depolarization
Successful competition results in myometrium relaxation
Appropriate serum lever is 5.5-7.0mg/dl
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Side effects of MgSOSide effects of MgSO44
Warmth and flushingRespiratory depressionCardiac conduction defectsDecrease in fetus renal clearanc
eLoss of muscle tone and drowsi
ness of neonatal
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NifedipineNifedipineA calcium-entry blockerBe effective in suppressing preterm l
aborMinimal matenal and fetal side effect
sSide effects include: headache, cutan
eous flushing, hypotension, tachycardia
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Prostaglandin synthetase Prostaglandin synthetase inhibitors inhibitorsIndomethacin is most commonly
usedSide effects: oligohydramnios, fe
tal intracranial hemorrhage, patent ductus arteriosis
Be used on a short-term basis
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Efficacy of tocolytic therapyEfficacy of tocolytic therapy
Prolong gestation ageImprove in neonatal survivalDecrease RDSIncrease in birth weight of infantBenefits do not accrue to infants
older than 34 weeks’ gestational age
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Contraindications of tocolytic thContraindications of tocolytic therapyerapy
Severe preeclampsiaSevere bleeding of placenta prev
ia and placenta abruptionChorioamnionitisIntrauterine growth restrictionFetal anomalies and fetal deathMamagemant must be individualiz
ed.
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Use of glucocorticoids for fetUse of glucocorticoids for fetal pulmonary maturational pulmonary maturation
Betamethasone 12mg Qd x 2 Dexamethasone 6mg Bid x 4Optimal benefit begins 24 hours af
ter therapy
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Labor and delivery of the prLabor and delivery of the preterm infantseterm infantsWith a vertex presentation, vagin
al delivery is preferredUse of outlet forceps and an epis
iotomy to shorten the second stage are advocated
For the breech, fetus estimated at less than 1500g,cesarean section
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