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  • Nathan Riley, MD

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

2017 Red Blend from Saved Wines


PB#171 - Published October 2016

Five Pearls

  1. Preterm labor carries significant risks to the newborn: the more premature, the worse the outcomes.

  2. 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.

  3. 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

  4. Latency antibiotics can improve outcomes for newborns in the setting of PPROM at <34 wga

  5. Magnesium sulfate can improve outcomes for newborns at risk of preterm birth at <32 wga

Background

- 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)

- regimens:

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

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