Christopher R. Graber, MD Salina Women’s Clinic Mar 3, 2010
Mar 20, 2016
Christopher R. Graber, MDSalina Women’s Clinic
Mar 3, 2010
DefinitionsRandom FactsRisk Factors for PTLTocolytics
Gr. tokos: childbirth, lytic: capable of dissolving
Identifying patients at high riskPreterm contractions aloneRecommendationsReferences
Term: 37-42 wgaPreterm: between 20 and 37 wgaLabor: contractions causing cervical changeInsufficient cervix: painless cervical dilation,
usually before 20 weeksTocolytic: any medicine given to inhibit
myometrial contractionsEtOH, MgSO4, CCA, betamimetics, NSAIDs
Preterm birth is a leading cause of neonatal morbidity and mortality
In the US, 11.5% of all births are preterm35% of health care $$ for infants75% of neonatal mortality50% of long-term neurologic impairments
The incidence of preterm birth is essentially the same as 40 years ago
Multiple gestationsPrior preterm birthPreterm premature ROMBacterial vaginosis (unclear if Rx helps)Genitial infectionsPeriodontal diseaseEnvironmental factors
Smoking, drug useLong periods of standing – 1 study
Etoh – mid 20th centuryMgSO4 – most commonly used, controversialCalcium Channel Blockers – newer
Nifedipine (Procardia)Betamimetics – most common outpatient
Ritodrine, turbutalineOxytocin antagonists – experimental
Atosiban
May prolong gestation for 2-7 daysAllow for steroids and/or transport
No clear “first-line” drugSide effects are common, adverse events are
rare but seriousDo NOT combine tocolytics
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 NICUMild and severe adverse effects more common in
MgSO4 group
Who to treat?Probability of progressive labor, gestational
age, risks of treatmentRegular uterine activity that does not decrease
with bed rest and hydrationContraindications
Severe preeclampsia, active vaginal bleeding (abruption), chorio, lethal abnormalities, advanced dilation, fetal indications
Document cervical dilation (?change)Consider fetal fibronectin
NPV 99%, PPV 50% for delivery in 2 weeksNo bleeding, cvx <3cm, NPV for 24h
Consider cervical sonoTransvaginal most accurate
Cervical Length (mm)
Fetal Fibronectin + (%)
Fetal Fibronectin – (%)
25 65 25
26-35 45 14
>35 25 7
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.
Recurrence risk of spontaneous preterm birth at <35wga in women with a prior preterm birth
Preterm contractions do not reliably predict cervical changeStudy: 760 women presenting with symptoms
18% delivered before 37wga3% delivered within 2 weeks of first presentation
Bed rest, pelvic rest, hydrationUncertain benefits, never provenPossible side effects: DVT, no income
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 courseOnly for transport
Consider amniocentesis for FLM
No clear “first-line” tocolytic drugsAntibiotics do not appear to prolong gestation
Reserve for GBS prophylaxisNeither maintenance treatment with
tocolytics nor repeated acute tocolysis improve perinatal outcomes
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
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.
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.