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Preterm LaborWilliams CH.36
Preterm Birth
Death, severe neonatal morbiditiesCommon before 26 weeksUniversal before 24 weeks
Worse Outcomes
Chronic lung diseaseGrade 3 and 4 intraventricular hemorrha
gePeriventricular leukomalacia
Threshold for neonatal mortality: 1600gThreshold for neonatal morbidity: 1900g
Cause of Preterm Birth
Medical and obstetrical complications Preeclampsia, fetal distress, IUGR, placenta abrupti
on
History of threatened abortion Lifestyle factors
Smoking, inadequate weight gain, drug abuse, age, short stature, occupation, poverty
Genetic factors Chorioamnionitis
Prior Preterm Birth
Incompetent Cervix
Mean cervical length at 24 weeks: 35 mm
Cervical Dilation 2~4 mm during 2nd trimester: predict birth prior to 35 weeks
Infections
Bacterial vaginosisTricomonas (low birth weight, preterm bir
th, perinatal death)Periodontal disease
Premature Membrane Rupture
PPROM
Incidence during 24~34 weeks1.7 % of pregnancy20 % of all prenatal deaths
7 % delivery delayed > 48 hoursBetter outcome
Volume of amniotic fluid after PPROMPrognositc importance before 26 weeks
PPROM < 23 weeks: lung hypoplasia
Antimicrobial therapyProlong latency period after PPROM
If chorioamnionitis is diagnosedFeverVaginal delivery
If PPROM beyond 34 weeksOxytocin to induction of laborC/S if indicated
Preterm Labor
Preterm Labor
Signs and symptomsPainful or painless uterine contractionsPelvic pressureMenstrual-like crampsWatery vaginal dischargeLow back pain
Diagnostic critiriaUterine contraction 4 in 20 mins8 in 60 mins with cervical changeCervical dilatation > 1 cmCervical effacement > 80%
Glucocorticoid
Betamethasone12mg IM stat and 24 hours laterEffective: 24 hours after initial doseEffect up to 7 daysAdverse effect:
Pulmonary edema InfectionDifficult glucose control in DM women
Bed rest (+)Hydration (-)Antimicrobials (-, if no PPROM)Emergency cerclage (+)
Drug to Inhibit Preterm Labor
Beta-Adrenergic Agonist
RitodrineBeta-adrenergic receptor desensitizationSide effect:
Pulmonary edemaHyperglycemiaArrhythmia
Magnesium Sulfate
Calcium antagonist Cleared almost by renal excretion 4 g loading dose 2 g/hr continuous dose Therapeutic range:
4~7 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
Prostaglandin Inhibitors
IndomethacinTotal 24 hours dose < 200 mgSide effect:
Oligohydramnios (reversible)
Calcium Channel Blockers
Nifedipine (adalat)Side effect:
HypotensionDecrease uteroplacental perfusion
Atosiban
Nonapeptide oxytocin analogueCompetitive antagonist of oxytocin-induc
ed contractionsSide effect:
Nausea, vomiting, headache, dizziness, money loss
18000 NTD/day
感恩