Management of Preterm Labor

Question 1

Preterm birth

Answer 1

Birth between 20 0/7 weeks and 36 6/7 weeks of gestation

Question 2

Preterm labor

Answer 2

Regular uterine contractions accompanied by a change in cervical dilation, effacement or both, or initial presentation with regular uterine contraction and dilation of at least 2 cm

Question 3

Percentage of women with the clinical diagnosis of preterm labor who give birth in the next 7 days

Answer 3

10%

Question 4

Therapeutic interventions associated with improved neonatal outcomes

Answer 4

antenatal corticosteroids and magnesium sulfate

Question 5

Which tests can be used to stratify risk for preterm delivery in patients who present with preterm contractions?

Answer 5

fetal fibronectin testing and cervical length measurements are associated with preterm birth but the positive predictive value of these tests alone is poor and should not be used exclusively to direct management in the acute setting

Question 6

Which patients with preterm labor are appropriate candidates for intervention?

Answer 6

Tocolytics

• at a gestational age at which a delay in delivery will provide benefit to the newborn
• Will benefit from the 48 hr effective window that tocolytics provide
• not at greater than 34 weeks gestation

Corticosteroids
- Not typically used in previability - exceptions may be following incidents which are known to induce preterm birth (abdominal surgery)

Question 7

Tocolytics in preterm delivery guidelines

Answer 7

• Effective for up to 48 hrs

- not used in previability (due to risks of therapy to mother exceeding the small potential benefits to the fetus)

Question 8

Contraindications to tocolysis

Answer 8

• IUFD
• Lethal fetal anomoly
• Nonreassuring fetal status
• Severe preeclampsia or eclampsia
• Maternal bleeding with hemodynamic instability
• Chorioamnionitis
• PPROM (in the absence of chorio, tocolysis may be used for maternal transport or steroid administration purposes)
• Maternal contraindications

Question 9

Should women with preterm contractions but without cervical change be treated?

Answer 9

No, especially with < 2 cm dilation

Question 10

Does the administration of antenatal corticosteroids improve neonatal outcomes? What are the recommendations?

Answer 10

Yes
- Single course of steroids for women 24-34 wks at risk of delivery in the next 7 days (including in women with ruptured membranes and twin gestation)
- May be considered in women at 23 weeks as well who are at risk in the next 7 days
Late preterm (34 0/7 wks - 36 6/7 wks) - data shows decrease in respiratory morbidity with steroids
Previable - based on family’s resuscitation desires

Question 11

Beneficial effects of corticosteroids in preterm birth

Answer 11

Reduced:

• Respiratory distress syndrome
• intracranial hemorrhage
• necrotizing enterocolitis
• death

Question 12

Indications for rescue course of steroids

Answer 12

Less than 34 wks, at risk of preterm delivery in the next 7 days, with prior course of steroids administered >14 days ago

• Can be given 7 days after initial course in certain cases.
• Lacking studies in the late preterm period
• Controversial in PPROM
• Given even if unlikely to receive full dose

Question 13

Steroids and doses

Answer 13

Betamethasone - 2 12 mg doses intramuscularly given 24 hours apart
Dexamethasone - 4 6 mg doses intramuscularly every 12 hrs
- No benefit to accelerated dosing

Question 14

What is the role for magnesium sulfate for fetal neuroprotection?

Answer 14

• Reduces the severity and risk of cerebral palsy in patients at <32 wks with risk of delivery
• No prolongation of pregnancy
• Increased incidence of minor maternal complications, but no increase in major maternal complications

Question 15

Does tocolytic therapy improve neonatal outcomes?

Answer 15

No

Question 16

Evidence-supported tocolytic agents

Answer 16

Beta-adrenergic receptor agonists, CCBs, and NSAIDs

Question 17

Agents not supported by evidence

Answer 17

Magnesium sulfate, oxytocin antagonists, and transdermal nitroglycerin agents (maternal risk)

Question 18

CCBs: Maternal side effects, fetal side effects, and contraindications

Answer 18

Maternal side effects: dizziness, flushing and hypotension; suppresion of HR, contractility and LVSP when used with Mg; elevated hepatic transaminases

Fetal side effects: none

Contraindications: hypotension and preload-dependent cardiac lesions (aortic insufficiency)

Question 19

NSAIDs

Answer 19

Maternal side-effects: nausea, esophageal reflux, gastritis and emesis; platelet dysfunction is rarely an issue in women without an underlying bleeding disorder

Fetal side effects: in utero constriction of ductus arteriosis and oligohydramnios (most severe with >48 hr use)

• Necrotizing enterocolitis in preterm infants
• Patent ductus arteriosis in newborn

Contraindications: platelet dysfunction or bleeding disorder, hepatic dysfunction, gastrointestinal ulcerative disease, renal dysfunction, and asthma (in women with hypersensitivity to aspirin)

Question 20

Beta-adrenergic receptor agonists

Answer 20

Maternal side-effects: tachycardia, hypotension, tremor, palpitations, SOB, chest discomfort, pulmonary edema, hypokalemia, and hyperglycemia

Fetal side effects: tachycardia

Contraindications: tachycardia-sensitive maternal heart disease and poorly-controlled DM

Question 21

Magnesium sulfate

Answer 21

Maternal side-effects: flushing, diaphoresis, nausea, loss of DTRs, respiratory depression, cardiac arrest, decreased HR, contractility, LVSP, and neuromuscular blockade when used with CCBs

Fetal side-effects: fetal depression

Contraindications: myesthenia gravis

Question 22

Pharmacologic treatment for uterine tachysystole

Answer 22

Terbutaline

Question 23

Should tocolytics be used after acute therapy?

Answer 23

No, only atosiban (not yet FDA approved) has been shown to be better than placebo as a maintenance drug to prevent preterm birth

Question 24

Is there a role for antibiotics in preterm labor?

Answer 24

No, antibiotics have actually been found to be associated with long-term harm in women with preterm labor and intact membranes

Question 25

Is there a role for nonpharmacologic management of women with preterm contractions or preterm labor?

Answer 25

No

Question 26

Is preterm labor managed differently in women with multiple gestations?

Answer 26

• Tocolytics have not been shown to be helpful and actually increase maternal complications in multifetal gestations
• Corticosteroids and magnesium sulfate are used the same as in singleton gestations.