#171 Management of Preterm Labor Flashcards
What is the leading cause of neonatal mortality?
Preterm birth
What is the preterm birth rate in the US?
12%
What percentage of preterm births are preceded by preterm labor?
50%
Preterm births account for what % of neonatal deaths?
70%
Preterm births account for what % of infant deaths?
36%
Preterm births account for what % of cases of long-term neurologic impairment in children?
25-50%
What is the definition of preterm birth?
Birth between 20w0d and 36w6d gestation
What is the definition of preterm labor?
- Regular uterine contractions accompanied by a change in cervical dilation, effacement, or both
- Initial presentation with regular contractions and cervical dilation of at least 2cm
What % of women with clinical diagnosis of preterm labor give birth within 7d of presentation?
Less thatn 10%
What therapeutic agents are currently thought to be clearly associated with improved neonatal outcomes?
Antenatal corticosteroids and targeted use of magnesium sulfate
Which tests can be used to stratify risk for preterm delivery in patients who present with preterm contractions?
Observational studies say that fetal fibronectin and cervical length may help reduce use of unnecessary resources, but findings have not been confirmed by RCTs.
Does fetal fibronectin testing have a high positive predictive value for preterm delivery?
No
Does a short cervical length for a women presenting with preterm contractions have a high positive predictive value for preterm delivery?
No
What percent of preterm labor spontaneously resolve?
30%
What percent of patients hospitalized for preterm labor deliver at term?
50%
For how long is tocolytic therapy generally effective for?
48 hours
When is it appropriate to administer tocolytics before viability?
When contractions occur after an event known to cause preterm labor, such as intra-abdominal surgery
What is the upper limit for the use of tocolytic agents to prevent preterm birth?
34 weeks
What are contraindications to tocolysis?
IUFD, lethal fetal anomaly, nonreassuring fetal status, severe preeclampsia or eclampsia, maternal bleeding with hemodynamic instability, chorioamnionitis, PPROM, maternal contraindication to tocolysis (agent specific)
What percentage of women presenting to triage for symptoms of preterm labor delivered before 37wks?
18%
What percentage of women presenting to triage for symptoms of preterm labor deliver within 2 weeks?
3%
Should you give prophylactic tocolytic therapy to women with preterm contractions, but no cervical change to prevent preterm delivery?
No evidence exists to support this use
Should women with preterm contractions without cervical change, with cervical dilation <2cm receive tocolytics?
Generally should not
What is the single most beneficial intervention for improvement of neonatal outcomes among patients who deliver preterm?
Antenatal corticosteroids
What is the indication for antenatal corticosteroids and timing for administration?
Indication is suspected preterm delivery within 7 days. Can consider it at 23 weeks. Give 24-34wks, 34-36w6d if have not previously received a course.
What is improved in neonates who received antenatal corticosteroids?
Lower severity, frequency, or both of RDS, intracranial hemorrhage, necrotizing enterocolitis, and death
When can you consider a rescue course of betamethasone?
Single repeat course in women less than 34 weeks who are at risk of preterm delivery in next 7d, and whose prior course of antenatal corticosteroids was administered more than 14d previously (can provide as early as 7d from prior dose, if indicated by clinical scenario)
What is the dosing of betamethasone for antenatal corticosteroids?
12mg q24 hours for 2 doses
What is the dosing of dexamethasone for antenatal corticosteroids?
6mg q12h for 4 doses
Are treatments with antenatal corticosteroids for <24hrs associated with improved fetal outcomes?
Yes, significant reductions in neonatal morbidity and mortality. First dose should be administered even if unlikely to be able to give second dose
Is there additional benefit seen with shorter dosage intervals (aka accelerated dosing) for antenatal corticosteroids when delivery appears imminent?
No
When should you administer magnesium sulfate for fetal neuroprotection (what gestational age)?
<32 weeks
What outcome is improved with administration of magnesium sulfate prior to 32 weeks?
Reduces the severity and risk of cerebral palsy in surviving infants
Does tocolytic therapy have any direct favorable effect on neonatal outcomes?
No
What tocolytics are supported as first line agents for up to 48 hours to allow for administration of antenatal steroids?
Beta-adrenergic receptor agonists, calcium channel blockers, or NSAIDs
What are maternal side effects of using calcium channel blockers as a tocolytic?
Dizziness, flushing, hypotension; suppression of heart rate, contractility, and left ventricular systolic pressure when used with magnesium sulfate; elevation of hepatic transaminases
What are fetal or newborn adverse effects of using calcium channel blockers as a tocolytic?
No known adverse effects
What are contraindications of using calcium channel blockers as a tocolytic?
Hypotension and preload-dependent cardiac lesions, such as aortic insufficiency
What are maternal side effects of using NSAIDs as a tocolytic?
Nausea, esophageal reflux, gastritis, emesis; platelet dysfunction is rarely of clinical significance in patients without underlying bleeding disorder
What are fetal or newborn adverse effects of using NSAIDs as a tocolytic?
In utero constriction of ductus arteriosus, oligohydramnios, necrotizing enterocolitis in preterm newborns, and patent ductus arteriosus in newborn (data conflicting)
*greatest risk with use for >48hrs
What are contraindications of using NSAIDs as a tocolytic?
Platelet dysfunction or bleeding disorder, hepatic dysfunction, gastrointestinal ulcerative disease, renal dysfunction, and asthma (in women with hypersensitivity to aspirin)
What are maternal side effects of using Beta-adrenergic receptor agonists as a tocolytic?
Tachycardia, hypotension, tremor, palpitations, shortness of breath, chest discomfort, pulmonary edema, hypokalemia, and hyperglycemia
What are fetal or newborn adverse effects of using Beta-adrenergic receptor agonists as a tocolytic?
Fetal tachycardia
What are contraindications of using Beta-adrenergic receptor agonists as a tocolytic?
Tachycardia-sensitive maternal cardiac disease and poorly controlled diabetes mellitus
What are maternal side effects of using magnesium sulfate as a tocolytic?
Flushing, diaphoresis, nausea, loss of DTRs, respiratory depression, and cardiac arrest; suppresses heart rate, contractility and left ventricular systolic pressure when used with CCBs; produces neuromuscular blockade when used with CCBs
What are fetal or newborn adverse effects of using magnesium sulfate as a tocolytic?
Neonatal depression (not seen in doses and duration for fetal neuroprotection)
What are contraindications of using magnesium sulfate as a tocolytic?
Myasthenia gravis
What tocolytics should be used with caution when use in conjunction with magnesium sulfate?
Beta-adrenergic receptor agonists and calcium-channel blockers
What is the only tocolytic that has demonstrated superiority as maintenance therapy in prolonging pregnancy?
Atosiban, but it is not available in the US
Is there a role for antibiotic use to prolong gestation or improve neonatal outcomes in women with preterm labor and intact membranes?
No. This recommendation is distinct from recommendation for antibiotic use for PPROM and GBS carrier status
Do nonpharmacologic methods (eg bed rest, hydration) in women with symptoms of preterm labor help prevent preterm delivery?
No. Furthermore, bed rest is associated with potential harm (VTE, bone demineralization, deconditioning, loss of employment)
Is there data to support use of antenatal corticosteroids in multifetal gestation with suspected preterm delivery?
Adequate data do not exist, but most experts recommend use
Should you use tocolytics for women with multifetal gestation?
Use of tocolytics in multiple gestations has been associated with greater risk of maternal complications, such as pulmonary edema. Have not been shown to reduce risk of preterm birth or improve neonatal outcomes
