Tocolytic drugs are used in preterm labor to:
Protect the fetus from infection.
Tie the cervix closed.
Allow time to give antenatal corticosteroids.
Prevent rupture of the membranes.
The Correct Answer is C
Choice A rationale
Tocolytic drugs, such as beta-adrenergic agonists (e.g., terbutaline) or magnesium sulfate, work by inhibiting uterine contractions. They do not possess any antimicrobial properties or mechanisms to protect the fetus from infection. Prophylactic antibiotics, not tocolytics, are administered to prevent or treat infections, especially in cases of prolonged rupture of membranes. The primary action is solely on smooth muscle relaxation, not immune response.
Choice B rationale
Tocolytic drugs function as uterine relaxants, suppressing uterine muscle contractions to delay preterm birth. Tying the cervix closed, a procedure known as a cerclage, is a surgical intervention used to prevent miscarriage or preterm birth in women with cervical insufficiency. This is a structural solution, completely different from the pharmacological mechanism of tocolytics which acts on smooth muscle cells.
Choice C rationale
Tocolytic medications delay labor, providing a crucial window to administer antenatal corticosteroids like betamethasone or dexamethasone. These corticosteroids require 24 to 48 hours to be effective, crossing the placenta to accelerate fetal lung maturity by stimulating surfactant production. This reduces the risk of respiratory distress syndrome, intraventricular hemorrhage, and necrotizing enterocolitis in the preterm infant.
Choice D rationale
Tocolytic drugs do not prevent the rupture of membranes. The rupture of membranes, known as amniorrhexis, is a physical event caused by the breakdown of the amniotic sac. Tocolytics act on the uterine muscle to inhibit contractions, which is a different physiological process. They can sometimes be used after membranes have ruptured to delay delivery, but they don't prevent the rupture itself.
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Correct Answer is A
Explanation
Choice A rationale
A fern pattern on a microscope slide is the definitive diagnostic sign of premature rupture of membranes (PPROM). This occurs when amniotic fluid, which contains sodium chloride, dries on the slide, forming a crystalline, fern-like pattern. This positive "ferning" test confirms the presence of amniotic fluid, indicating that the membranes have ruptured.
Choice B rationale
White vaginal discharge is a common finding during pregnancy and is not indicative of PPROM. This discharge, known as leukorrhea, is a result of increased estrogen production and blood flow to the vaginal area. It is a normal physiological change and does not signify ruptured membranes.
Choice C rationale
A negative fetal fibronectin test indicates a low probability of preterm birth within the next one to two weeks. It does not diagnose PPROM. While PPROM often leads to preterm birth, the fFN test is a predictive tool for labor, whereas ferning is a direct diagnostic test for membrane rupture.
Choice D rationale
The pH of vaginal fluid is typically acidic, ranging from 3.8 to 4.5. Amniotic fluid, however, is alkaline, with a pH of 7.0 to 7.5. Therefore, a vaginal fluid pH of 4.5 would be considered normal and would not indicate the presence of alkaline amniotic fluid, which would raise the pH to above 6.5.
Correct Answer is C
Explanation
Choice A rationale
Respiratory depression in the newborn is a condition often associated with maternal opioid use during labor, as these drugs can cross the placental barrier and affect the fetal central nervous system. The situation described, involving prolonged rupture of membranes (PROM) for 24 hours, does not directly cause respiratory depression. Instead, it significantly increases the risk of infection.
Choice B rationale
Fetal hypoxia is caused by a lack of oxygen reaching the fetus, which can result from issues such as placental abruption, cord compression, or maternal hypotension. While infection from prolonged rupture of membranes can indirectly lead to fetal distress, it is not the primary or most direct concern. The most immediate and significant risk is ascending bacterial infection from the vagina.
Choice C rationale
Prolonged rupture of membranes (PROM) for more than 24 hours significantly increases the risk of ascending bacterial infection from the vagina into the uterus. This can lead to chorioamnionitis, a bacterial infection of the amniotic fluid and membranes, which can then progress to maternal sepsis. The bacteria can also cross the placenta or be ingested by the fetus, leading to fetal sepsis.
Choice D rationale
Precipitous labor is defined as a rapid labor that lasts less than three hours from the onset of contractions to birth. This condition is not directly related to prolonged rupture of membranes. A history of precipitous labor is an independent risk factor for future rapid births, and prolonged rupture of membranes has no effect on the speed of cervical dilation and effacement.
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