Preterm LaboPreterm Laborr

General hospital of Tianjin medical university

Zhang Xuhong

In USA:morbidity 10% Neonatal morbidity and mortality 50%-70%

In China:morbidity 5%-15%

Neonatal mortality 15%

DefinitionDefinition

Preterm labor is defined as that occuring after 20 weeks and before 37 completed weeks of gestation.

Etiology and risk Etiology and risk factorsfactorsEtiologic subtypes of pret

erm laborOther undiagnosed condi

tions and problemsHigh risk factors

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

Undiagnosed Undiagnosed conditionsconditions Placental originSilent infectionImmunologic etiologyUterine originCervical origin

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

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

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

Infection-cervical Infection-cervical pathwaypathway

Bacteria vaginosisVaginal-cervical infections and

cervical lengthFibronectin test (1)positive:22-24weeks, predict

preterm labor (2)negative:low risks

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

ManagementManagement

Adequate hydration and bed restVaginal examnationCultureAntibiotic therapyLaboratory testsUltrosonic examinationTocolytic therapy

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.

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.

Cultures of vagina diachargeCultures of vagina diacharge

Main organisms in the etiology of preterm labor:

Group B streptococcus

Ureaplasma

Myoplasma

Gardnerella vaginalis

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.

Antibiotic therapyAntibiotic therapy

Penicillin is the first chioceA 7-day course of ampicillin and/

or erythromycin( no allergy)Clindamycin or vacomycin( aller

gy)

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

Utrasonic examinationUtrasonic examinationDetect document presentationAssess cervical lengthRule out fetus congenital malformati

onAssess fetal weight Uterine anomaly:

uterus bicornis （双角） uterus septus （纵隔）

Uterine tocolytic therapyUterine tocolytic therapy

Uterine tocolytic agents

(1) Magnesium sulfate

(2) Nifedipine

(3) Prostoglandin synthetase inhibitors

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

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

NifedipineNifedipineA calcium-entry blockerBe effective in suppressing preterm l

aborMinimal matenal and fetal side effect

sSide effects include: headache, cutan

eous flushing, hypotension, tachycardia

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

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

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.

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

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