Final answer:
A 28-year-old woman four days postpartum with symptoms of anxiety, irritability, and trouble sleeping likely has postpartum blues, a common and usually self-limiting condition after childbirth that typically resolves within two weeks.
Step-by-step explanation:
The most likely diagnosis for a G1P1 (a woman who has given birth once) who is four days postpartum and experiencing symptoms like trouble sleeping, feeling anxious, and irritability is likely postpartum blues (Option B). These symptoms are common and usually resolve within two weeks after delivery. Thyroid issues have different symptoms, clinical depression usually has a longer course, and anxiety disorders tend to have specific triggers or are persistent. While some discomfort is normal after childbirth, the symptoms described here fit with the typical presentation of postpartum blues. It is important for healthcare providers to monitor the situation to ensure that it does not progress into a more serious condition such as postpartum depression.