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9.Preterm Labor
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9.Preterm Labor

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  • 1. Preterm Labor General hospital of Tianjin medical university Zhang Xuhong
  • 2.
    • In USA:morbidity 10%
    • Neonatal morbidity and mortality 50%-70%
    • In China:morbidity 5%-15%
    • Neonatal mortality 15%
  • 3. Definition
    • Preterm labor is defined as that occuring after 20 weeks and before 37 completed weeks of gestation.
  • 4. Etiology and risk factors
    • Etiologic subtypes of preterm labor
    • Other undiagnosed conditions and problems
    • High risk factors
  • 5. There are three etiologic subtypes of preterm labor
    • Spontaneous preterm birth
    • Preterm premature rupture of the membranes
    • Induction of labor for medical indication:
    • preeclamsia,cardiac disease
  • 6. Undiagnosed conditions
    • Placental origin
    • Silent infection
    • Immunologic etiology
    • Uterine origin
    • Cervical origin
  • 7. High risk factors
    • Socioeconomic factors : race
    • Medical and obstetric factors
    • (1)Preterm birth occurred before
    • (2)Second-trimester abortion and repeated spontaneous first-trimester abortions
    • (3)Bleeding, urinary tract infection, uterine anomalies, polyhydramnios,multiple gestation…
    • (4)Bad nutritional status,stress and anxiety
  • 8. Clinical 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
  • 9. Evaluation
    • Gestational age: 20-37;LMP and EDC
    • Fetal weight: biparietal diameter and lenth of thighbone
    • Presenting part:
    • Fetal monitoring: NST( non-stress test
  • 10. Infection-cervical pathway
    • Bacteria vaginosis
    • Vaginal-cervical infections and cervical length
    • Fibronectin test
    • (1)positive:22-24weeks, predictpreterm labor
    • (2)negative:low risks
  • 11. Diagnosis
    • 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
  • 12. Management
    • Adequate hydration and bed rest
    • Vaginal examnation
    • Culture
    • Antibiotic therapy
    • Laboratory tests
    • Ultrosonic examination
    • Tocolytic therapy
  • 13. Hydration and bed rest
    • If 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.
  • 14. Vaginal examination
    • No membrane rupture and no contraindications.
    • Ascertain cervical length and dilation.
    • Ascertain the station and nature of the presenting part of the fetus.
    • Monitor for uterine contractions, its presence, frequency and intensity.
  • 15. Cultures of vagina diacharge
    • Main organisms in the etiology of preterm labor:
    • Group B streptococcus
    • Ureaplasma
    • Myoplasma
    • Gardnerella vaginalis
  • 16. Diagnosis of bacteria vaginosis
    • Vaginal PH > 4.5 (3.8- 4.4)
    • Whiff test (+) : amine odor after addition of 10% potassium hydroxide
    • Presence of clue cells
    • Milky discharge
    • The diagnosis can be made by the presence of three of four clinical signs.
  • 17. Antibiotic therapy
    • Penicillin is the first chioce
    • A 7-day course of ampicillin and/or erythromycin( no allergy)
    • Clindamycin or vacomycin( allergy)
  • 18. Laboratory test
    • Complete blood cell count
    • Random blood glucose lever
    • Serum electrolytes lever(Ca 2+ , Mg 2+ )
    • Urinalysis (protein, glucose, WBC,RBC)
    • Urine culture and sensitivity
  • 19. Utrasonic examination
    • Detect document presentation
    • Assess cervical length
    • Rule out fetus congenital malformation
    • Assess fetal weight
    • Uterine anomaly:
    • uterus bicornis (双角)
    • uterus septus (纵隔)
  • 20.  
  • 21.  
  • 22. Uterine tocolytic therapy
    • Uterine tocolytic agents
    • (1) Magnesium sulfate
    • (2) Nifedipine
    • (3) Prostoglandin synthetase inhibitors
  • 23. Magnesium sulfate
    • The first choice of tocolytic therapy
    • Compete with calcium ions for entry into the cell at the time of depolarization
    • Successful competition results in myometrium relaxation
    • Appropriate serum lever is 5.5-7.0mg/dl
  • 24. Side effects of MgSO 4
    • Warmth and flushing
    • Respiratory depression
    • Cardiac conduction defects
    • Decrease in fetus renal clearance
    • Loss of muscle tone and drowsiness of neonatal
  • 25. Nifedipine
    • A calcium-entry blocker
    • Be effective in suppressing preterm labor
    • Minimal matenal and fetal side effects
    • Side effects include: headache, cutaneous flushing, hypotension, tachycardia
  • 26. Prostaglandin synthetase inhibitors
    • Indomethacin is most commonly used
    • Side effects: oligohydramnios, fetal intracranial hemorrhage, patent ductus arteriosis
    • Be used on a short-term basis
  • 27. Efficacy of tocolytic therapy
    • Prolong gestation age
    • Improve in neonatal survival
    • Decrease RDS
    • Increase in birth weight of infant
    • Benefits do not accrue to infants older than 34 weeks’ gestational age
  • 28. Contraindications of tocolytic therapy
    • Severe preeclampsia
    • Severe bleeding of placenta previa and placenta abruption
    • Chorioamnionitis
    • Intrauterine growth restriction
    • Fetal anomalies and fetal death
    • Mamagemant must be individualized.
  • 29. Use of glucocorticoids for fetal pulmonary maturation
    • Betamethasone
    • 12mg Qd x 2
    • Dexamethasone
    • 6mg Bid x 4
    • Optimal benefit begins 24 hours after therapy
  • 30. Labor and delivery of the preterm infants
    • With a vertex presentation, vaginal delivery is preferred
    • Use of outlet forceps and an episiotomy to shorten the second stage are advocated
    • For the breech, fetus estimated at less than 1500g,cesarean section
  • 31.  

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