The correct answer is D. Topical corticosteroids.
Involvement of the umbilicus with urticarial papules and plaques progressing into vesicles and bullae is most consistent with pemphigoid gestationis, also called herpes gestationis. The first-line treatment of pemphigoid gestationis is topical corticosteroids.
Early delivery at 36 weeks and ursodeoxycholic acid may be treatment options for cholestasis of pregnancy, though this may present with palmoplantar involvement or elevated bile acids. Phototherapy and systemic corticosteroids may be considered if first-line therapy with topical corticosteroids fails, though this is not essential at this time; additionally, systemic corticosteroids may need to be considered if there are pustules that would be suggestive of pustular psoriasis of pregnancy (i.e., impetigo gestationis).
References
- Genovese G, Derlino F, Berti E, Marzano AV. Treatment of Autoimmune Bullous Diseases During Pregnancy and Lactation: A Review Focusing on Pemphigus and Pemphigoid Gestationis. Front Pharmacol. 2020;11:583354. Published 2020 Oct 2.