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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

Pre-Term Labor

Christopher R. Graber, MD

Salina Women’s Clinic

September 27, 2011

(revised from Mar 2010)

  • 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
  • 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
random facts
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
risk factors for ptl
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
  • 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
  • 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
mgso4 vs nifedipine
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
mgso4 for neuroprotection
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
high risk
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
identify high risk patients
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
prior preterm birth
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.

preterm contractions
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
other random facts
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
recommendations level a
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
recommendations level a1
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
recommendations level b
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
  • 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.