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Pre-Term Labor

Pre-Term Labor. Christopher R. Graber, MD Salina Women’s Clinic September 27, 2011 (revised from Mar 2010). Introduction. Definitions Random Facts Risk Factors for PTL Tocolytics Gr. tokos : childbirth, lytic : capable of dissolving Identifying patients at high risk

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Pre-Term Labor

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  1. Pre-Term Labor Christopher R. Graber, MD Salina Women’s Clinic September 27, 2011 (revised from Mar 2010)

  2. Introduction • Definitions • Random Facts • Risk Factors for PTL • Tocolytics • Gr. tokos: childbirth, lytic: capable of dissolving • Identifying patients at high risk • Preterm contractions alone • Recommendations • References

  3. Definitions • Term: 37-42 wga • Preterm: between 20 and 37 wga • Labor: contractions causing cervical change • Insufficient cervix: painless cervical dilation, usually before 20 weeks • Tocolytic: any medicine given to inhibit myometrial contractions • EtOH, MgSO4, CCA, betamimetics, NSAIDs

  4. Random Facts • Preterm birth is a leading cause of neonatal morbidity and mortality • In the US, 11.5% of all births are preterm • 35% of health care $$ for infants • 75% of neonatal mortality • 50% of long-term neurologic impairments • The incidence of preterm birth is essentially the same as 40 years ago

  5. Risk Factors for PTL • Multiple gestations • Prior preterm birth • Preterm premature ROM • Bacterial vaginosis (unclear if Rx helps) • Genitial infections • Periodontal disease • Environmental factors • Smoking, drug use • Long periods of standing – 1 study

  6. Tocolytics • Etoh – mid 20th century • MgSO4 – most commonly used, controversial • Calcium Channel Blockers – newer • Nifedipine (Procardia) • Betamimetics – most common outpatient • Ritodrine, turbutaline • Oxytocin antagonists – experimental • Atosiban

  7. Tocolytics • May prolong gestation for 2-7 days • Allow for steroids and/or transport • Betamethasone 12mg IM q24h x 2 doses • No clear “first-line” drug • Side effects are common, adverse events are rare but serious • Do NOT combine tocolytics

  8. Controversy for MgSO4

  9. MgSO4 vs. Nifedipine • 2005: 192 patients, 24 to 33.6 wga, randomized to MgSO4 or Nifedipine • Primary outcome: arrest of preterm labor – prevention of delivery for 48 hours with uterine quiesence • Primary outcome – MgSO4 87% vs. Nifedipine (72%) • No differences – del within 48h, gestational age at del, birth prior to 37 or 32 weeks. • MgSO4 newborns spent more time in NICU • Mild and severe adverse effects more common in MgSO4 group

  10. MgSO4 for Neuroprotection • ACOG Committee Opinion 455, March 2010 • Observational studies in ‘90’s showed fewer neurologic complications if MgSO4 exposure for preterm del • Led to several large studies • Meta-analysis suggests that MgSO4 decreases risk for cerebral palsy (RR 0.71, 95% confidence 0.55-0.91) • No effect on fetal/infant death • Serious maternal complications not more common

  11. MgSO4 for Neuroprotection

  12. High Risk? • Who to treat? • Probability of progressive labor, gestational age, risks of treatment • Regular uterine activity that does not decrease with bed rest and hydration • Contraindications • Severe preeclampsia, active vaginal bleeding (abruption), chorio, lethal abnormalities, advanced dilation, fetal indications

  13. Identify High Risk Patients • Document cervical dilation (?change) • Consider fetal fibronectin • NPV 99%, PPV 50% for delivery in 2 weeks • No bleeding, cvx <3cm, NPV for 24h • Consider cervical sono • Transvaginal most accurate

  14. Prior Preterm Birth Recurrence risk of spontaneous preterm birth at <35wga in women with a prior preterm birth Fetal fibronectin and cervical length (transvaginal) assessed at 24wga. From: Iams JD, et al. The Preterm Prediction Study: recurrence risk of spontaneous preterm birth. Am Journal of Obstetrics and Gynecology. 1998; 178: 1035-1040.

  15. Preterm Contractions • Preterm contractions do not reliably predict cervical change • Study: 760 women presenting with symptoms • 18% delivered before 37wga • 3% delivered within 2 weeks of first presentation • Bed rest, pelvic rest, hydration • Uncertain benefits, never proven • Possible side effects: DVT, no income

  16. Other random facts • Women with multiple gestations are at high risk for PTL but are also at high risk for pulmonary edema with MgSO4 or turbutaline. • Repeated courses of tocolysis? • Limited benefits for initial course • Only for transport • MgSO4 for neuroprotection? • Consider amniocentesis for FLM

  17. Recommendations – Level A • No clear “first-line” tocolytic drugs • Antibiotics do not appear to prolong gestation • Reserve for GBS prophylaxis • Neither maintenance treatment with tocolytics nor repeated acute tocolysis improve perinatal outcomes

  18. Recommendations – Level A • Tocolytics may prolong pregnancy 2-7 days to allow for transport and ANCS (the most beneficial intervention for true PTL) • There are no current data to support the use of salivary estriol, Home Uterine Activity Monitoring (HUAM), or BV screening as strategies to identify or prevent PTL

  19. Recommendations – Level B • Cervical ultrasound and/or fetal fibronectin have good negative predictive value and may be useful in determining women at high risk • Amniocentesis for FLM may be used during preterm labor episodes • Bed rest, hydration, and pelvic rest do not appear to improve the rate of preterm birth

  20. References • ACOG Practice Bulletin. Assessment of Risk Factors for Preterm Birth. Number 31, October 2001, reaffirmed 2008. • ACOG Practice Bulletin. Management of Preterm Labor. Number 43, May 2003, reaffirmed 2008. • ACOG Committee Opinion . Magnesium Sulfate Before Anticipated Preterm Birth for Neuroprotection. Number 455, March 2010. • Elliott, JP, et al. In Defense of Magnesium Sulfate. Obstetrics & Gynecology. 113(6):1341-1348, June 2009. • Grimes, DA, et al. Magnesium Sulfate Tocolysis: Time to Quit . Obstetrics & Gynecology. 108(4):986-989, October 2006. • Iams JD, et al. The Preterm Prediction Study: recurrence risk of spontaneous preterm birth. Am erican Journal of Obstetrics and Gynecology. 1998; 178: 1035-1040. • Lyell DJ. Magnesium sulfate compared with nifedipine for acute tocolysis of preterm labor: a randomized controlled trial. Obstetrics & Gynecology July 2007; 110(1): 61-7.

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