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PRETERM LABOR

PRETERM LABOR. Melissa Tebrock MD MAJ, MC, USA Dewitt Army Community Hospital 9 June 2005. Disponible en: http://www.usuhs.mil/fap/capcon/256,1,PRETERM LABOR. Preterm Labor. Definition Incidence Etiology Prevention/Surveillance Diagnosis Management. Preterm Labor (PTL).

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PRETERM LABOR

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  1. PRETERM LABOR Melissa Tebrock MD MAJ, MC, USA Dewitt Army Community Hospital 9 June 2005 Disponible en:http://www.usuhs.mil/fap/capcon/256,1,PRETERM LABOR

  2. Preterm Labor • Definition • Incidence • Etiology • Prevention/Surveillance • Diagnosis • Management

  3. Preterm Labor (PTL) ACOG defines Preterm Labor as regular contractions with cervical change before 37 weeks’ gestation

  4. PTL: Incidence • 10-12% of all pregnancies • Related to 80% of perinatal mortality • Single greatest cause perinatal morbidity and mortality in western countries • Most common cause of hospitalization during pregnancy

  5. Preterm Delivery (PTD) • Despite medical advances, PTL and preterm births rates not improving • Medical advances = greater # complicated pregnancies and successful PTD • Rate of U.S. preterm birth increasing • 1995: 25th in world infant mortality • Huge health care costs • Continued ethical concerns

  6. PTL Outcomes • Developmental delay • Cerebral Palsy & neurological deficits • Poor school grades • Chronic pulmonary issues • vision//hearing impairment • Family, school, economic burden

  7. Maternal Factors: Age (<18 and >40) Race (nonwhite) Poverty Smoking Drugs/EtOH Prior preterm birth Maternal Factors: Prior 2nd trimester loss or bleeding Psychological stress Poor nutrition Low prepregnancy weight and gain PTL: Risk Factors

  8. PTL: Risk Factors: • Uterine: • Anatomic anomaly: -fibroids, placenta previa • Increased volume: -multiple gestation, polyhydramnois • Trauma/abruption • Cervical incompetence/short cervix • Oligohydramnios

  9. PTL and Infection • History of previous genital infection • Current genital infection • Current systemic infection, i.e. pneumonia, periodontal disease, appendicitis

  10. PTL: Genital Infections • Often subclinical • Correlate more w/ PTL/PTB < 31 wks • Anaerobes and genital mycoplasmas • Ascend vagina, cervix, triggers leukocyte recruitment, cytokine production, enzymes which weaken protective cervical mucous, cause PTL & preterm premature rupture of membranes

  11. PTL: Genital Infections • Chorioamnionitis • Chlamydia & gonorrhea: irritate cervix • Group B Streptococcus: amniotic irritation • Asymptomatic bacturia, UTI, Pyelonephritis • +/- Trichomonas, Candida, Ureaplasma urealyticum, Mycoplasma hominis

  12. PTL and Bacterial Vaginosis • Known association between PTL and BV • Found in 10-25% pregnant women, <3% will have issues • 50% asymptomatic • Treatment of BV in high risk women shown to  PPROM, not necessarily PTL • Trials for screening and treatment have varying results

  13. Etiology PTL Often multifactorial Often idiopathic No risk factors in 50% of preterm births

  14. Preterm Premature Rupture of Membranes (PPROM) • PPROM: rupture membranes prior to 37 weeks and at least 1 hour before onset labor • Ave 8% all pregnancies • 20-40% before 37 weeks • Same Risk Factors as PTL • Infection often the culprit

  15. PTL: Prevention and Early Detection Education Programs: no evidence of efficacy in low risk pregnancy Intensive education in high-risk groups has not decreased PTD rates in US Effective in Europe

  16. Home Uterine Activity Monitoring (HUAM) • Theory: patients may not recognize early uterine activity associated with PTD • HUAM studied as method to predict preterm labor in high risk women • Tocodynamometer readings, daily phone calls from RN/provider • Mixed study results, insufficient data and cost have limited applicability

  17. Risk Scoring Systems Multiple scoring systems devised No one better than another Unsuccessful in predicting PTL May have role in predicting PTD

  18. Transvaginal Cervical Ultrasonography • Provides reliable length, dilation, effacement • More accurate than digital exam • Risk PTD  w/ cervix length  • PPV 43%, NPV 89% if > 2.5 cm for PTD, accepted safe length is 3 cm • Not currently recommended for routine screening • Use in high risk/symptomatic patients • Cervical funneling also useful predictor for PTL/PTD- more study needed

  19. Biochemical Markers • Multiple markers for PTL found: • Fetal fibronectin • Salivary Estriol • IL-6 • Estradiol-17B • Progesterone • Not currently recommended as routine screening tools

  20. Fetal Fibronectin (FFN) • Present throughout body, in blood • Is a glue like substance that helps maintain placental attachment to the decidua • Not detectable in vaginal secretions after 20 weeks to term • If present after 20 weeks in cervical/vaginal fluids= disruption maternal-fetal boundaries • Negative if < 50g/ml

  21. Fetal Fibronectin • High specificity: after a negative test, 124 of 125 women will not deliver in next 14 days • Positive result: 1 in 6 women will deliver in next 14 days (does not=delivery) • May aid in early discharge vs. increased vigilance • FDA approved

  22. Progesterone and PTL Prevention • Inhibits oxytocin effect of prostaglandin F2a and stimulation of alpha adrenergics, acting as a tocolytic • No known teratogenic effects • May cause pain, swelling, bruising from injection, but no known maternal/fetal metabolic or hemodynamic effects

  23. Progesterone and PTL Prevention • Multiple studies show weekly IM injection of 250-1000 mg alpha-hydroxyprogesterone caproate from 16-37 weeks in women at risk for PTL reduced PTD rates, w/ NNT range 2.4-7 • ? Reduced NEC, IVH, perinatal morbidity • Other studies did not demonstrate benefit • NOT FDA approved & not ACOG recommended

  24. Asymptomatic Infection Screening and Antibiotic Prophylaxis • Some evidence to screen for asymptomatic bacturia, though not currently recommended • No recommendation to screen for BV routinely • Screen, treat based on risk, symptoms, personal comfort level • Prophylaxis in asymptomatic women not recommended

  25. PTL/PPROM Evaluation • History: • Ask about Risk Factors • Dating (preterm) • Onset symptoms (back pain, pressure, cramps, contractions, fluid leak, bleeding) • Other medical history

  26. PTL/PROM Exam • Maternal vitals: temp, BP, P, RR • Maternal quick physical • Fetal heart rate (FHR) pattern • Contraction pattern • Fetal size, presentation • DO NOT DO DIGITAL EXAM IF ROM SUSPECTED OR WILL DO FFN TEST!

  27. PTL/PPROM Exam • Sterile Speculum Exam: • Look for pooling, trailing membranes • Nitrazine, ferning • Cervix visualization • FFN if available • Wet prep, cultures (GBS, GC, Chl)

  28. PTL/PPROM studies • Ultrasound: • cervix length, AFI, gestational age • CBC, UA: r/o infection • Preeclampsia labs as needed • Amniocentesis for lung maturity as needed

  29. PTL • 4 contractions in 20 minutes or • 8 contractions in 60 minutes with • PROM • Progressive cervical change • Effacement greater than 80% • Cervical dilation greater than 1 cm • Dilation >3cm, positive FFN concerning regardless of presence of contractions

  30. Initial Thoughts • Hydration, bed rest, pelvic rest • No evidence this is beneficial • Consider early transfer • Is delivery imminent? • Condition mother and fetus • Capabilities your/transfer center

  31. Medical Management of Preterm Labor • Steroids • Tocolysis • Antibiotics

  32. PTL: Steroids • Reduces RDS, IVH, NEC, infant mortality • Only treatment shown to improve fetal survival in PTL • Criteria: • Delivery likely within 7 days • fetus 24-34 weeks • Able to delay delivery 24-48 hrs

  33. PTL: Steroids • Use between 32-34 weeks arguable- may no benefit RDS but may benefit IVH up to 34 weeks • Regimens: -Betamethasone 12 mg IM, 2 doses, q 24 hr -Dexamethasone 6 mg IM, 4 doses, q 12 hr

  34. PTL: Steroids • Maternal Adverse Effects • Short term: glucose control, pulmonary edema, infection • Long term: no adverse effects • Fetal Adverse Effects • No long term effects of single course • Multiple course associated w/ infection, abnormal development

  35. Tocolysis Only evidence showing acute tocolysis is beneficial for short term PTL management, and not for PTD No evidence that maintenance tocolysis is beneficial fro PTL or PTD at this time in large studies

  36. PTL: Tocolysis • Goal: prolong pregnancy 2-7 days for steroid efficacy and transfer to higher level of care, • Goal: reduce contractions (< 6/hr) and stop cervical change

  37. Tocolysis • Criteria: -Assure maternal/fetal well being first • no contraindication to rx • no contraindication to prolonging pregnancy • Diagnosis clear • Cervix <4cm • 24-34 weeks

  38. Tocolysis • General Contraindications • Acute fetal distress • Chorioamnionitis • Severe preeclampsia/eclampsia • Fetal demise • Fetal maturity • Maternal hemodynamic instability

  39. Tocolytic Agents • Beta-mimetics • Ritodrine, terbutaline • Magnesium Sulfate • Indocin • Nifedipine (CCBs)

  40. Beta-mimetics • Function: • Stimulate beta2 receptors in uterus and lung, decrease contractility • Cross react with beta2 in heart • Efficacy: shown to prolong labor 24-48 hours to allow transfer and steroid benefits • Ritodrine (FDA approved) and Terbutaline • Neither beneficial to neonatal mortality, but studies done prior to steroid use

  41. Beta-mimetics Terbutaline • IV and multiple SC dosing effective in temporarily stopping contractions • SC 0.25 mg q 1-4 hours • IV 0.01 mg/min,  0.005 mg/min to maximum of 0.025 mg/min • Oral dose not effective in PTL (ok for PTCx) Ritodrine: iv only, 0.1 mg/min, increase by 0.05 mg/min q 30 minutes, titrate down & stop 12 hours after contractions stopped (max 0.35 mg/min)

  42. Maternal Side Effects: Beta-mimetics • Tremor, nervousness, HA, N/V, anxiety, SOB, palpitations, chest pain • Hyperglycemia, electrolyte abnormalities • Fluid retention, hyperkinesias • Hypotension, pulmonary edema, arrhythmias, MI, tachyphylaxis

  43. Fetal Side Effects of Beta-mimetics • Tachyarrhythmia, heart failure, MI, hypotension • Hyper/hypoglycemia, hyperbilirubinemia • Death

  44. Contraindications: Beta-mimetics • Absolute: • Maternal cardiac disease, eclampsia, severe pre-eclampsia, hemorrhage, uncontrolled hyperthyroid, diabetes • Relative: • Diabetes, hypertension, migraines, sepsis

  45. Magnesium Sulfate • Widespread use • No clear evidence showing efficacy in delaying/preventing PTD • Controversy: ?may increase infant mortality, but studies show less gross motor dysfunction in infants • ? Works by calcium antagonist activity • Load 4-6 gm IV, then 1-4 gm/hour, no wean • Oral dose not effective

  46. Magnesium Sulfate • Side effects: • N/V, HA, warmth, sweating, flushing, hypocalcemia, tetany, muscular paralysis, hypotension, palpitations, pulmonary edema, respiratory arrest (toxic levels), cardiac arrest (rare) • Pulmonary edema worse when used with terbutaline • Crosses placenta, no adverse fetal effects (may have less reactivity)

  47. Magnesium Sulfate • Contraindications: • Myasthenia Gravis, renal failure, hypocalcemia • Exam: • Fluid I/O, UOP, VS, mental status hourly • Pulm exam • Reflexes (loss when level >8) • Therapeutic level: 5.5-7.5 mg/dl, toxic >15 • Antidote: calcium gluconate

  48. Indocin • Inhibits prostaglandins/cytokines that trigger labor • Well studied, use limited by side effects • Can inhibit PTL for 48 hrs in <37 weeks • Use in cases w/ good dating, <32 weeks • Dosing: • 100mg rectal dose, repeat x1 in 1-2 hours if contractions persist • 25-50 mg orally q4-6 hours <48 hours for cessation of contractions

  49. Indocin • Well tolerated by mom, causing usual NSAID side effects • Does not decrease neonatal mortality, may increase IVH, jaundice, NEC risk after 32 weeks • Can cause PPH, constrict fetal ductus arteriosis, oligohydramnios

  50. Nifedipine • Inhibit contraction of smooth muscle • Very efficacious • Nifedipine most widely studied CCB • Some studies show as efficacious or better than beta-mimetics with less side effects • Gaining popularity as tocolytics of choice

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