PRETERM LABOR

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PRETERM LABOR

• Everything You Need To Know
• (and Nothing You Dont)

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Definition and Scope

• Labor occurring prior to the completion of the
  37th week of gestation (259 days)
• Contractions with cervical change
• May or may not lead to preterm delivery
• Most common cause of preterm delivery
• Rates have not changed over the last 40 years
  despite intensive research

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Definition and Scope

• Preterm Birth
• Affects 1 in 10 pregnancies in the USA
• 75 of fetal deaths
• Infant born less than 1500g is 200 times more
  likely to die than one born gt2500g
• Infants born less than 2500g are 10 times more
  likely to have neurological impairment
• Goal Prevent Preterm Birth

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Etiology

• Most cases are idiopathic
• Low socioeconomic status
• Nonwhite
• Young or advanced maternal age
• Low prepregnancy weight
• Previous preterm delivery (16-37)
• Smoking, cocaine
• Multiple second-trimester losses

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Etiology

• Preterm rupture of membranes
• Has its own set of etiologies
• Results in preterm labor in gt80 of cases
• Racial / Ethnic groups
• White patients more likely to present with
  preterm labor
• Non-white more likely to present with preterm
  rupture of the membranes

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Etiology

• Uterine Abnormalities
• Unicornate or bicornate uterus
• Submucosal myomata
• Cervical incompetence
• Painless cervical dilation
• May lead to preterm labor or PPROM
• DES exposure

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Infection?

• Suspected Organisms
• BV (Gardnerella)
• Chlamydia
• Ureaplasma
• Trichomonas
• Weak associations, no benefit of antibiotics in
  preventing PTL or PTD

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Assessing Risk

• Several methods advocated
• Cervical length studies
• Digital exams
• 2 cm dilation at 28 weeks showed increased risk
  in one study
• 1 cm dilation in early third trimester associated
  with increased risk
• Large study found 7 at 28 weeks and 32 at 32
  weeks with dilation and no increased PTL or PTD

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Assessing Risk

• No screening test or score successful in
  predicting PTL with any significant positive
  predictive value
• FFN has a useful negative predictive value, but
  is NOT recommended by ACOG as a screening tool
• Vaginal pH, uterine monitoring jury is out

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Prevention

• Uterine monitoring
• Randomized trials with conflicting data
• Patients benefit from the nurse visit not
  necessarily the uterine monitor
• More useful in patients with multiple gestation
• May be useful in patients with a history of
  PTL/PTD or at high risk

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Prevention

• Oral Tocolytics
• Usually ß-agonists
• No benefit shown in randomized, placebo
  controlled trials
• Bed rest
• Most common treatment
• Studies show no benefit

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Prevention

• 17-P Therapy
• 17 alpha hydroxyprogesterone caproate
• Shows 37 reduction in PTL / PTD in patients with
  previous PTL / PTD in two large, randomized,
  placebo-controlled trials
• Start weekly injections at 16 weeks and continue
  until 36 weeks
• Not for tocolysis or adjunct therapy

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Management

• 28 year old, G3, P1102 at 27 weeks 4 days
• by LMP (c/w 18 week USG) presents to LD
• Triage complaining of uterine contractions
• for the last 2 hours. She has no bleeding,
• no leakage of fluid, and her baby is moving
• normally. Contractions are painful and about
• three minutes apart.

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Management

• Initial Assessment
• History and Physical
• HPI Timing, duration, quality, associated
  symptoms
• Ob history preterm birth x 1 at 31 weeks
• Gyn history history of infertility, baby by IVF
• Medical history unremarkable
• Exam
• Vitals, Chest, Abdomen
• Fetal Monitor with Toco
• Digital exam

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Management

• Closed, Thick Cervix
• Fluids
• UA
• Vaginal wet prep
• Monitoring, may d/c home without change
• ? FFN if done before digital exam

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Management

• Pre-Term Labor
• Cervical change documented by the same examiner
  with continued contractions
• 2cm / gt80 effaced
• If appropriate gestational age, start tocolysis

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Tocolysis

• Goals
• Transport to tertiary care center
• Administer corticosteroids
• Prolong pregnancy
• More effective when started prior to 3 cm
  dilation
• No data suggest that tocolysis improves any index
  of long-term prenatal or perinatal morbidity or
  mortality beyond steroid adminstration
• ? Placement of cervical cerclage

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Tocolysis

• Indications
• Less than 34 weeks gestation (morbidity and
  mortality is within 1 of term infants after 34
  weeks gestation)
• No evidence of infection
• Viable
• No life-threatening maternal complications

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Tocolysis

• Contraindications
• Acute fetal distress
• Chorioamnionitis
• Severe Preeclampsia
• Fetal demise
• Maturity
• Maternal hemodynamic instability

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Tocolysis

• Magnesium Sulfate
• Most commonly used in tertiary centers
• Low incidence of maternal side effects
• Decreases smooth muscle contractility by
  interfering with calcium transportation (theory)
• No better than other tocolytics but easier to
  control (drip) and fewer side effects

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Magnesium Sulfate

• Dosing
• Try to maintain levels of 5.5-7 mg/dl
• Usual dose is 6g loading dose followed by 3g/hour
  infusion
• Magnesium levels can be monitored to check for
  theraputic range or if soft signs of toxicity are
  present
• May increase dosage if no signs of toxicity

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Magnesium Sulfate

• Contraindications
• Myasthenia Gravis
• Myasthenia Gravis
• MYASTHENIA GRAVIS!!!!
• Renal failure
• Severe hypocalcemia

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Magnesium Sulfate

• Side effects
• Maternal flushing or warmth
• Headache
• Nausea
• Dry mouth
• Dizziness
• Blurred vision

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Magnesium Sulfate

• Toxicity
• Loss of deep tendon reflexes (serum concentration
  around 8mg/dl)
• Mental status change / loss of consciousness
• Respiratory depression
• Pulmonary Edema
• Profound Hypotension
• Cardiac Arrhythmias

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Magnesium Sulfate

• Toxicity (continued)
• Treat according to symptoms NOT levels
• Calcium Gluconate
• Comes in 10 ml vials
• Each vial contains 4.5 mEq of Calcium Gluconate
• Recommended dose is 4.5-7 mEq in adults
• Can be given IM or in a 10 dilution IV
• In respiratory depression or arrest, think of the
  ABCs first, then give Calcium

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Terbutaline

• ?-agonist
• Promotes smooth muscle relaxation
• May be given IV or Sub-cutaneously
• Rapid onset of action
• No better than magnesium for PTL higher
  incidence of maternal side effects

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Terbutaline

• Contraindications
• Maternal cardiac rhythm disturbance
• Cardiac disease
• Poorly controlled diabetes
• Thyrotoxicosis
• Severe hypertension

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Terbutaline

• Side Effects / Toxicity
• Maternal tachycardia
• Fetal tachycardia
• Hyperglycemia, hypokalemia
• Hypotension
• Cardiac insufficiency
• Arrhythmias
• Myocardial ischemia
• Maternal death

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Terbutaline

• Other Uses
• Asthma
• P.O. tocolysis (not effective)
• Subcutaneous pump (may be effective)
• Uterine relaxation / fetal recussitation

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Indomethacin

• Powerful Anti-inflammatory
• Inhibits prostaglandin synthesis
• Readily crosses the placenta
• Often used in conjunction with other tocolytic
  therapy (e.g., magnesium)
• Shown effective in prolonging pregnancy 48-72
  hours

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Indomethacin

• Contraindications
• Asthma
• Coronary artery disease
• GI bleed
• Oligohydramnios
• Renal failure
• Fetal cardiac lesion
• Gestational age gt32 weeks

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Indomethacin

• Side effects / toxicity
• Rare maternal effects
• GI bleeding (rare)
• Mask fever (rare)
• Fetal effects
• May constrict ductus most profound in patients
  gt32 weeks
• May cause oligohydramnios
• May increase risk of IVH

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Other Agents

• Nifedipine
• Calcium Channel blocker
• Smooth muscle relaxer
• Torodol
• Anti-inflammatory
• More GI side effects than Indomethacin
• Ritodrine
• Only FDA approved drug for PTL
• Very rarely used ?-agonist

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Corticosteroids

• For now, the ONLY evidence-based rational for
  tocolysis
• Proper course of steroids within a 48-hour period
  reduced the risk of neonatal IVH by greater than
  50 and RDS by 28
• Benefit seen prior to 34 weeks
• Also reduces risk for NEC, ROP, and neonatal death

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Corticosteroids

• Dosing
• Two IM doses of 12.5 mg Betamethasone, 24 hours
  apart
• Full benefit is reached 24 hours AFTER the second
  dose
• Also may give 6 mg Dexamethasone IM x 4 doses, 12
  hours apart
• Increased risk of cystic para-ventricular
  leukomalacia and cerebral palsy with Dex

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Corticosteroids

• Controversies
• Multiple course administration
• No evidence of harm to mother or fetus
• No evidence of benefit over one course
• Accelerated dosing
• No evidence early course completion is better
  than single dose
• May be a candidate for a new course if possible

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Antibiotics

• Used ONLY to prevent Group B ß-streptococcus
  infection in the neonate
• Fetus should receive two doses if possible
• Dosing for PCN
• 5 million units loading dose
• 2.5 million units every 4 hours
• May use ampicillin
• Use clindamycin with PCN allergy

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Antibiotics

• Massive trials show antibiotics do not increase
  time to delivery in PTL
• Culture-based use of antibiotics in pre-term
  labor is controversial
• Use PCN if at all possible most group B strep is
  sensitive

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Summary for PTL

• Does the patient have PTL?
• Cervical exam
• Document advanced dilation or change
• Toco monitor
• Is the patient a candidate for tocolysis?
• lt34 weeks
• Viable
• No contraindications

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Summary for PTL

• What method should be used?
• Use magnesium if not contraindicated
• Best tolerated
• Easiest dosing to control
• Indomethacin generally considered second line,
  then Terbutaline
• What else should be given?
• Steroids (ALWAYS)
• Antibiotics

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Summary for PTL

• What other considerations?
• Ultrasound for fetal weight
• Neonatology consultation
• What if the first line drug is not working?
• Consider gestational age
• Consider adding additional agent or re-bolus of
  current medication
• Note interactions CAREFULLY