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

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