Preterm Labor

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Preterm Labor

• Williams CH.36

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Preterm Birth

• Death, severe neonatal morbidities
• Common before 26 weeks
• Universal before 24 weeks

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Worse Outcomes

• Chronic lung disease
• Grade 3 and 4 intraventricular hemorrhage
• Periventricular leukomalacia

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• Threshold for neonatal mortality 1600g
• Threshold for neonatal morbidity 1900g

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Cause of Preterm Birth

• Medical and obstetrical complications
• Preeclampsia, fetal distress, IUGR, placenta
  abruption
• History of threatened abortion
• Lifestyle factors
• Smoking, inadequate weight gain, drug abuse, age,
  short stature, occupation, poverty
• Genetic factors
• Chorioamnionitis

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Prior Preterm Birth
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Incompetent Cervix

• Mean cervical length at 24 weeks 35 mm
• Cervical Dilation 24 mm during 2nd trimester
  predict birth prior to 35 weeks

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Infections

• Bacterial vaginosis
• Tricomonas (low birth weight, preterm birth,
  perinatal death)
• Periodontal disease

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Premature Membrane Rupture

• PPROM

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• Incidence during 2434 weeks
• 1.7 of pregnancy
• 20 of all prenatal deaths
• 7 delivery delayed gt 48 hours
• Better outcome
• Volume of amniotic fluid after PPROM
• Prognositc importance before 26 weeks
• PPROM lt 23 weeks
• lung hypoplasia

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• Antimicrobial therapy
• Prolong latency period after PPROM
• If chorioamnionitis is diagnosed
• Fever
• Vaginal delivery

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• If PPROM beyond 34 weeks
• Oxytocin to induction of labor
• C/S if indicated

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Preterm Labor
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Preterm Labor

• Signs and symptoms
• Painful or painless uterine contractions
• Pelvic pressure
• Menstrual-like cramps
• Watery vaginal discharge
• Low back pain

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• Diagnostic critiria
• Uterine contraction 4 in 20 mins
• 8 in 60 mins with cervical change
• Cervical dilatation gt 1 cm
• Cervical effacement gt 80

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Glucocorticoid

• Betamethasone
• 12mg IM stat and 24 hours later
• Effective 24 hours after initial dose
• Effect up to 7 days
• Adverse effect
• Pulmonary edema
• Infection
• Difficult glucose control in DM women

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• Bed rest ()
• Hydration (-)
• Antimicrobials (-, if no PPROM)
• Emergency cerclage ()

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Drug to Inhibit Preterm Labor
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Beta-Adrenergic Agonist

• Ritodrine
• Beta-adrenergic receptor desensitization
• Side effect
• Pulmonary edema
• Hyperglycemia
• Arrhythmia

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Magnesium Sulfate

• Calcium antagonist
• Cleared almost by renal excretion
• 4 g loading dose? 2 g/hr continuous dose
• Therapeutic range
• 47 mEq/L
• 1 mEq/L 1.2 mg/dl 0.5 mmol/L
• Deep tendon reflex disappear
• 10 mEq/L
• Respiratory arrest
• 12 mEq/L

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Prostaglandin Inhibitors

• Indomethacin
• Total 24 hours dose lt 200 mg
• Side effect
• Oligohydramnios (reversible)

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Calcium Channel Blockers

• Nifedipine (adalat)
• Side effect
• Hypotension
• Decrease uteroplacental perfusion

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Atosiban

• Nonapeptide oxytocin analogue
• Competitive antagonist of oxytocin-induced
  contractions
• Side effect
• Nausea, vomiting, headache, dizziness, money loss
• 18000 NTD/day

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