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Pre-term labor: treatment

Definition: presence of uterine contractions of sufficient frequency and intensity that causes progressive effacement and dilation of the cervix prior to term gestation (between 20 and 37 wk). The earlier it occurs, the less the odds of survival of the fetus

What exactly causes it? Nobody really knows, but there are certain things that can predispose pts to it

Risk Factors:

  • decidual hemorrhage
  • abruption
  • mechanical factors such as uterine overdistension from multiple gestation or polyhydramnios),
  • cervical incompetence/short cervix
  • trauma
  • cone biopsy
  • uterine distortion: fibroids, müllerian duct abnormalities
  • cervical inflammation/infection
  • maternal inflammation/fever : UTI
  • nonwhite race,
  • extremes of maternal age (<17 y or >35 y),
  • low socioeconomic status
  • low prepregnancy weight.
  • hormonal changes (eg, mediated by maternal or fetal stress)
  • uteroplacental insufficiency
  • HTN
  • IDDM
  • IVDU
  • Tobacco/ETOH

How to assess pt?

  • check integrity of cervix w/ serial digital exams
  • transvaginal US of cervix
  • Labs: GC/CL, RPR, APTT, whiff test for BV, lupus anticoagulant
  • Hysterosalpingogram(preconceptual)



  • MgSO4
    • check CBC, follow urine output in mom,
    • watch Mom for toxicity: respiratory depression or even cardiac arrest, flushing, nausea, headache, drowsiness, and blurred vision
    • watch BABY for toxicity: it CROSSES PLACENTA, respiratory and motor depression of neonate
    • dc magnesium sulfate therapy after 48 hours in most patients unless the gestational age is less than 28 weeks when a gain of an additional 3-4 days may significantly reduce neonatal morbidity and mortality
    • first-line tocolytic for the pregnant patient in early preterm labor (<30 wk) or preterm labor associated with polyhydramnios.
    • PG inhibitor
    • cross placenta and can impair fetal renal function,oligohydramnios
    • can cause fetal ductus arteriosus to close after 32weeks, so it is not usually given after that
    • if fetal anuria persistm increases odds of fetal DEMISE
    • ccb, inhibits uterine contraction
    • SFx: maternal tachycardia, palpitations, flushing, headaches, dizziness, and nausea
    • Beta agonists are rarely used because of adverse maternal and fetal effects: tachycardia, pulmonary edema,palpitations, hyperglycemia
  • Tocolytics : side effects
    • What are tocolytics? Rx which stop labor contractions
    • Why are they used? Mainly to buy time to allow fetal lung maturity, stabilize mom/fetus
    • Does this requiring monitoring? It depends; for certain drugs, yes especially for BP and HR in mom


  1. fetal death/distress/demise
  2. IUGR
  3. fetus older than 37 wks
  4. chorioamnionitis
  5. cervical dilation of 4 cm
  6. MOM has : PIH, eclampsia, active bleeding, cardiac dz

The RX

  • MgSO4: blocks neuromuscular transmission and prevents release of ACH
  • Muscle weakness
  • Respiratory depression
  • Low bp, tachycardia
  • BETA agonists: MOA relax smooth muscle
  • RITODRINE: inc HR, hyperglycemia, inc BP, pulmonary edema
  • TERBUTALINE: inc HR, hyperglycemia, inc BP, pulmonary edema, fetal tachycardia and hypoglycemia
  • NIFEDIPINE: constipation, HA, hypotension, lightheadedness
  • INDOMETHACIN: PG inhibitor–> inh renin–>inhibit aldosterone–> hyperNatremia, hyperKalemia, edema, HTN, in more severe cases: renal failure/nephritis