The first-line pharmacologic management for dysmenorrhea is:

Rationale:
A. Caput succedaneum is edema of the scalp that crosses suture lines and results from pressure on the presenting part during delivery, not a true hemorrhage.
B. Cephalohematoma is a subperiosteal hemorrhage, meaning blood collects between the periosteum and the skull bone. It is typically firm, well-defined, and does not cross suture lines. It may appear several hours after birth and usually resolves spontaneously over weeks to months.
C. Subdural hemorrhage involves bleeding beneath the dura mater, often associated with trauma or birth complications, but it is deeper than a cephalohematoma and may cause neurological signs.
D. Subarachnoid hemorrhage occurs in the space between the arachnoid and pia mater; it is not limited to the periosteum and is rare in uncomplicated deliveries.

Rationale:
A. Warfarin is used for anticoagulation in certain cardiac conditions but is not the primary treatment for post-surgical infection.
B. IV immune globulin is used for conditions like Kawasaki disease or immunodeficiencies, not typical post-operative infections.
C. IV antibiotics should be considered because the child presents with fever, lethargy, chest pain, and shortness of breath four weeks after heart surgery, which are concerning for post-operative infection or bacterial endocarditis. Prompt initiation of IV antibiotics is critical to prevent serious complications.
D. Aspirin may be indicated for anti-inflammatory or antiplatelet purposes in some cardiac conditions, but it does not treat infection.