Why can erythema nodosum appear during pregnancy?

What does the evidence show for erythema nodosum?

• The lumps often begin as warm, painful areas on the fronts of the lower legs, then change color as they fade. Joint discomfort or fever can accompany them. A clinician should evaluate the pattern rather than interpreting every painful red leg area as the same condition. 1
• Pregnancy is an associated trigger, but an evaluation may identify another cause such as a recent streptococcal infection, inflammatory bowel disease or a medicine exposure. Describe throat symptoms, bowel symptoms, travel or infection history, and recent medication changes to help guide testing. 2
• Testing should follow the history and examination. Some people need blood tests, a throat sample, imaging or a skin biopsy, while not everyone needs the same extensive investigation. The aim is to understand the underlying setting as well as the skin findings. 2
• General erythema nodosum advice may mention anti-inflammatory pain medicines, but pregnancy changes that decision. FDA advises avoiding NSAIDs from 20 weeks onward unless specifically directed by a clinician. Prescribed low-dose aspirin has a separate role and should not be stopped based on this general warning. 3
• New pain, redness or swelling mainly in one leg, especially with chest pain or shortness of breath, needs immediate assessment. Do not label a possible clot as a skin flare. A fever of 100.4°F or higher also warrants prompt medical attention in pregnancy. 4

When should I call my provider about erythema nodosum?

Seek immediate assessment for marked one-sided leg swelling, redness or pain, or a temperature of 100.4°F or higher. Call emergency services for chest pain, shortness of breath or faintness. Do not assume these are explained by a skin condition.