Drug hypersensitivity reactions during pregnancy range from mild cutaneous manifestations to severe systemic events such as anaphylaxis. In addition to reactions occurring during gestation, pre-existing drug allergy labels may substantially influence therapeutic decisions and obstetric care.

To review the spectrum of drug hypersensitivity reactions during pregnancy, including pre-existing suspected drug allergies and reactions occurring during gestation, with emphasis on clinical manifestations, obstetric implications, and management strategies.

A systematic search of PubMed, Embase, and the Cochrane Library was conducted in November 2025 using terms related to pregnancy and drug hypersensitivity. Studies evaluating hypersensitivity reactions, drug allergy labels, or allergy assessment during pregnancy were considered eligible. Nine studies met the inclusion criteria, yielding ten independent datasets for qualitative synthesis.

Eight datasets evaluated β-lactam antibiotics and two evaluated low-molecular-weight heparins. The prevalence of self-reported penicillin allergy ranged from 6% to 8%, whereas confirmed allergy was consistently below 10% following formal evaluation. Severe reactions, including anaphylaxis, were uncommon. Inaccurate allergy labeling was associated with increased use of alternative antibiotics and potential adverse obstetric implications. In contrast, low-molecular-weight heparins were predominantly associated with delayed type IV cutaneous hypersensitivity reactions, which were generally managed by therapeutic substitution.

Drug hypersensitivity during pregnancy encompasses distinct clinical patterns according to the drug class involved. While β-lactam-associated reactions are primarily characterized by inaccurate allergy labeling and its therapeutic consequences, heparin-associated reactions are more commonly related to delayed cutaneous hypersensitivity. Structured risk assessment and appropriate diagnostic evaluation may optimize maternal and fetal outcomes.