Obgyno Wino Podcast Episode 34 - Management of Preterm Labor
"Why should I fear death? If I am, death is not. If death is, I am not. Why should I fear that which cannot exist when I do?" —Epicurus
PB#171 - Published October 2016
Preterm labor carries significant risks to the newborn: the more premature, the worse the outcomes.
Given high risk for long-term morbidity in extremely premature infants, focusing on comfort as opposed to aggressive resuscitation at time of delivery is reasonable through a shared medical decision-making process.
Corticosteroids can improve outcomes for newborns at risk of preterm birth at <34 wga (and some as late as 36w5d) if delivery anticipated within the next 7 days
Latency antibiotics can improve outcomes for newborns in the setting of PPROM at <34 wga
Magnesium sulfate can improve outcomes for newborns at risk of preterm birth at <32 wga
- Around 10% of babies are born before 37 wga
- why are we concerned? higher risk of neonatal mortality, respiratory distress, sepsis, intracranial bleeding, and long-term issues like neurodevelopmental challenges
- preterm labor definition: regular uterine contractions + cervical dilation ≥ 2 cm between 20 wga and 36w6d ga
- <10% of women who present that meet these criteria actually deliver within 7 days
So a patient presents with contractions preterm...
- you could look with a speculum exam, collect fetal fibronectin, and/or get an endovaginal ultrasound
- utility of ultrasound and FFN haven't been validated through RCTs, though observational data suggests they may be helpful in identifying patients truly at risk for preterm birth; FFN alone has poor predictive value (CONSIDER THE WHOLE CLINICAL PICTURE)
- if she looks like she's in labor, especially if >32 wga, digital exam of the cervix may be warranted - we will review prevention of preterm labor in a future episode...
When should we be worried about preterm delivery?
- consistent regular contractions and evidence of cervical dilation are good signs
- in 30% of patients presenting w/ preterm prodromal labor, the process will cease spontaneously; only 50% of patients admitted for preterm labor concerns will end up delivering at term (SO BE JUDICIOUS AND THOUGHTFUL)
Pearl: ~20% of patients who present with preterm contractions without cervical dilation will deliver before 37 wga <5% will deliver within 2 weeks of presentation
Can we stop preterm labor?
- Sometimes, but tocolytic therapy is only thought to be effective for 48 hrs (just so happens to buy you enough time to get corticosteroids on board if indicated)
- tocolysis is generally not recommended after 34 wga
- since 30% of preterm labor will resolve without any intervention, even patients with advanced cervical dilation (2 cm) at <34 can generally be observed without tocolytics, and particularly so if no cervical dilation is found
- b-adrenergics don't tocolyze well and carry significant maternal cardiovascular risks (but OK for antepartum uterine tachysystole)
What's the cut off for viability?
- <20 weeks is considered previable (no intervention indicated)
- 23 wga to ~26 wga can be considered periviable
- this NICHD calculator can be used in your counseling to guide delivery/management plan
Pearl: Just because we can resuscitate a baby doesn't mean that we should. Delivery of a peri-viable newborn must include risks and benefits of delivery methods to mom and risk and benefits of preterm delivery and resuscitation to the newborn.
What's the role of corticosteroids?
- stimulates the development of alveoli in premature fetal lungs in order to optimize transition to external environment
- can significantly improve outcomes
- recommend a single course if patient presents with preterm labor (or need for delivery due to maternal health concerns like early-onset severe preeclampsia) between 23 wga and 33w6d if you anticipate delivery within 7 days
- can repeat the course if greater than 2 weeks have passed after first course
- can recommend single course between 34 wga and 36w5d if i) no prior steroids, ii) membranes intact, iii) patient not diabetic (and don't delay delivery to complete course)
a. betamethasone 12-mg IM q24 hrs for 2 doses
b. dexamethasone 6-mg IM q12 hrs for 4 doses
Should I mag or should i no?
- if <32 wga, start mag for fetal neuroprotection
- mag isn't a reliable tocolytic agent
- if patient is on mag for fetal neuroprotection, adding on a tocolytic agent can still be considered, but be careful with b-agonists and Ca-channel blockers (synergistic w/ mag sulfate, so may cause hypotension); go with indomethacin
Should I recommend antibiotics?
- intrauterine infection is a well known cause of preterm labor and delivery
- antibiotics haven't been found to be helpful outside of PPROM at <34 wga ("latency" abx)
- latency antibiotics have been found to improve interval from time of PPROM to delivery, ↓ risk of chorio, neonatal infection, and need for neonatal oxygen therapy (Cochrane Review) in patients who present w/ PPROM at <34 wga
- the regimen:
2x days ampicillin 2 g IV q6hr PLUS erythromycin 250 mg IV q6hr THEN 5x days amoxicillin 250 mg PO q8hr PLUS erythromycin 333 mg PO q8hr
- erythromycin and azithromycin are equally efficacious, but the latter is cheaper and better tolerated from GI standpoint
- amoxicillin-clavulanic acid (augmentin) associated with higher risk of neonatal necrotizing enterocolitis (NEC) in some studies, therefore not recommended
- if PCN allergic:
Azithromycin 1 g PO x1 at time of admission PLUS 2x days cefazolin 1g IV q8hr THEN 5x days cephalexin 500 mg PO four times daily
- if severe PCN allergy, substitute cephalosporins for gentamicin/clindamycin
- at 34 wga, it's prudent to recommend IOL (risks versus benefits)
What can be done to prevent preterm delivery?
- hydration, bed rest, nor tocolytics in asymptomatic women haven't been found to be helpful prophylaxis against preterm delivery
- plus there's potential harm from decreased activity: ↑ risk VTE, ↑ bone demineralization, and general deconditioning
- Atosiban is a maintenance tocolytic that isn't FDA approved for use in the US
What about preterm delivery in multiple gestations?
- no clear data to support the benefit of steroids or mag sulfate for fetal neuroprotection in multiple gestations
- many experts extrapolate that benefit outweighs risk, though
- tocolytics: risks outweigh benefits in multiple gestations