Tocolytic Therapy for Preterm Labor Flashcards
What races have higher incidence of preterm labor?
AA
T or F. Women with a previous Hx of preterm labor have an increased risk of having another preterm child
T. Although this risk can be offset with progesterone admin
What are the other risk factors of preterm labor?
low socioeconomic statuepoor nutritional statusextremes of agesmoking
What is thought to cause preterm labor?
multifactorial with an underlying infection as the initiating factor in up to 40% of preterm births
Why would an infection stimulate labor?
Activation of the immune system can produce inflammatory cytokines and prostaglandins that result in uterine contractions and weakening of the amniotic membranesNOTE: ABX have NOT been shown to decrease the risk of preterm birth
What are tocolytics used for?
They can temproarily inhibit uterine contractions (but have not been shown to prevent preterm labor before 37 weeks)
What is the primary goal of tocolytic therapy?
to allow admin of glucocorticoids to reduce the risk of the prematurity related complications of respiratory distress syndrome, necrotizing entercolitis, and hemorrhage ORto facilitate maternal transport to a more appropriate facility for birth
What is the most commonly used tocolytic?
Magnesium sulfate
How does magnesium sulfate prevent labor?
It decreases the availability of calcium by blocking intracellular channels, which decreased myometrial contractility
What are some possible maternal AEs to magnesium sulfate?
flushing, N/V, blurry vision, HA, lethargy, hypotension, and pulmonary edema
What are some signs of magnesium sulfate toxicity?
loss of patellar reflexes followed by decreased urine outputRespiratory depression can occur
How would magnesium sulfate affect the neonatal heart?
causes non-clinically significant bradycardia
What are some suggested protective mechanisms of magnesium sulfate?
-can prevent gross motor dysfunction (cerebral palsy)
Although it is widely used as a tocolytic agent, the literature does not support MS as being effective in withholding delivery for 48 hrs, preventing preterm birth, or reducins the risk for neonatal morbidity BUT is most likely neuroprotective for the fetus
What are some beta-mimetics used in labor delay?
Terbutaline,Salbutamol, and Hexoprenaline
T or F. Beta mimetics should not be used for prolonged tocolysis (48-72+ hrs) because of the potential for serious maternal cardiac toxicity and death
T.
How do beta-mimetics work?
They function as beta-adrenergic receptor agonists, relaxing smooth muscle including the myometrium via Gimechanisms (cAMP) causing suppression of the availability of intracellular calcium and the activity of myosin light-chain kinases, thus suppressing myometrial contractility
Are beta-mimetics effective?
They decrease the risk of delivery within 48 hrs and showa trend toward reduction within 7 days, but there is no reduction in preterm birth or neonatal morbidity.
How do beta-mimetics compare to other tocolytics?
They are notsuperior and not as effective asnifedipine in reducing the risk of delivery within 7 days or before 34 weeks gestation
What is the most commonly used beta-mimetic?
Terbutaline given as a subQ injection
What are some AEs to beta-mimetics?
tachycardia, tremor, dyspnea, chest discomfort, palpitations, and hyperglycemia
Beta-mimetics are contraindicated in what pts.?
those with known cardiac disease or poorly controlled diabetes
What are calcium channel blockers most commonly used for?
Tx of HTN, angina, and coronary artery disease by preventing reuptake of calcium ions via voltage-dependent calcium channelsThese work to prevent labor osnet because the lack of intracellular calcium inhibits actin and myosin, and thus myometrial activity
What are the main advantages of nifedipine in preventing labor?
Significantly reduced risk of delivery within 7 days of initiations as well as a reduction in delivery rates before 34 weeks, as well as decreased risk of respiratory distress, necrotizing enterocolitis, and intraventricular hemorrhage
What is the most commonly used prostaglandin inhibitor to treat preterm labor?
Indomethacin.
How do prostaglandins induce labor?
they increase gap junction size which facilitates increased intracellular calcium leading to myometrial contractility
T or F. Overall, studies have shown that prostaglandin inhibitors are better tolerated and have a lwoer discontinuation rate owing to side effects than other tocolytics such as beta-mimetics and magnesium sulfate
T.
What effects do prostaglandin inhibitors have on the fetus?
Premature closure of the ductus arteriosus and oligohydramnios if used for too longIt seems to be a safe and effective tocolytic when used for a short period of time, however
