Preterm Labor
Williams CH.36
Preterm Birth

Death, severe neonatal morbidities
Common before 26 weeks
 Universal before 24 weeks

Worse Outcomes
Chronic lung disease
 Grade 3 and 4 intraventricular
hemorrhage
 Periventricular leukomalacia

Threshold for neonatal mortality: 1600g
 Threshold for neonatal morbidity: 1900g

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
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 vaginosis
 Tricomonas (low birth weight, preterm
birth, perinatal death)
 Periodontal disease

Premature Membrane
Rupture
PPROM

Incidence during 24~34 weeks
1.7 % of pregnancy
 20 % of all prenatal deaths


7 % delivery delayed > 48 hours


Volume of amniotic fluid after PPROM


Better outcome
Prognositc importance before 26 weeks
PPROM < 23 weeks:

lung hypoplasia

Antimicrobial therapy


Prolong latency period after PPROM
If chorioamnionitis is diagnosed
Fever
 Vaginal delivery


If PPROM beyond 34 weeks
Oxytocin to induction of labor
 C/S if indicated

Preterm Labor
Preterm Labor

Signs and symptoms
Painful or painless uterine contractions
 Pelvic pressure
 Menstrual-like cramps
 Watery vaginal discharge
 Low back pain


Diagnostic critiria
Uterine contraction 4 in 20 mins
 8 in 60 mins with cervical change
 Cervical dilatation > 1 cm
 Cervical effacement > 80%

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

Bed rest (+)
 Hydration (-)
 Antimicrobials (-, if no PPROM)
 Emergency cerclage (+)

Drug to Inhibit Preterm Labor
Beta-Adrenergic Agonist
Ritodrine
 Beta-adrenergic receptor desensitization
 Side effect:

Pulmonary edema
 Hyperglycemia
 Arrhythmia

Magnesium Sulfate




Calcium antagonist
Cleared almost by renal excretion
4 g loading dose 2 g/hr continuous dose
Therapeutic range:



Deep tendon reflex disappear


4~7 mEq/L
1 mEq/L = 1.2 mg/dl = 0.5 mmol/L
10 mEq/L
Respiratory arrest

12 mEq/L
Prostaglandin Inhibitors
Indomethacin
 Total 24 hours dose < 200 mg
 Side effect:


Oligohydramnios (reversible)
Calcium Channel Blockers
Nifedipine (adalat)
 Side effect:

Hypotension
 Decrease uteroplacental perfusion

Atosiban
Nonapeptide oxytocin analogue
 Competitive antagonist of oxytocininduced contractions
 Side effect:

Nausea, vomiting, headache, dizziness,
money loss
 18000 NTD/day

感恩