A pregnant 30-year-old woman complains of persistent numbness on the palmar surface of her right hand and of pain in her right arm. Her symptoms are more severe in the morning. Neurologic examination reveals a sensory deficit in the right thumb and the index and middle fingers, as well as on the lateral half of the ring finger. The patient has weakness when abducting the thumb. Which of the following is considered first-line treatment?

Choice A reason: Gabapentin is used for neuropathic pain but is not considered first-line therapy for mild-to-moderate carpal tunnel syndrome, particularly in pregnancy. Choice B reason: Anti-inflammatories, such as NSAIDs, may relieve symptoms but are generally avoided in pregnancy due to potential fetal risks and are not considered first-line for mechanical compression neuropathies. Choice C reason: Corticosteroids can reduce inflammation but are not typically the initial treatment due to potential systemic effects, especially in pregnancy. Choice D reason: Splinting of the wrist, particularly a neutral-position splint, is considered the first-line treatment for carpal tunnel syndrome during pregnancy. It helps reduce compression on the median nerve and relieve nocturnal symptoms safely.