Bimekizumab (also known by the brand name Bimzelx) is a biological medication that works by blocking specific proteins in the immune system. It is used to treat various inflammatory conditions. In this study, researchers are looking at how much of this medication passes into breast milk when nursing mothers receive the treatment. This helps understand the safety of the medication for breastfeeding mothers and their infants.

Psoriatic arthritis – A chronic inflammatory joint condition that occurs in some people with psoriasis. It causes joint pain, stiffness, and swelling that can affect any part of the body. The condition typically affects the fingers, toes, wrists, and lower back, causing joints to become swollen and tender. The symptoms can vary from mild to severe, and they may develop gradually or suddenly.

Axial spondyloarthritis – A chronic inflammatory arthritis that primarily affects the spine and sacroiliac joints. The condition causes pain and stiffness in the back and hips, particularly in the morning or after periods of inactivity. It can lead to reduced flexibility in the spine and may affect other joints in the body. The symptoms typically begin in early adulthood and develop gradually over time.

Hidradenitis suppurativa – A chronic skin condition that causes small, painful lumps to form under the skin. These lumps typically develop in areas where skin rubs together, such as the armpits, groin, and under the breasts. The condition can cause the formation of tunnels under the skin and scarring. The symptoms tend to be long-lasting and can flare up periodically.

Plaque psoriasis – A chronic skin condition characterized by thick, red patches covered with silvery scales. These patches, known as plaques, most commonly appear on the elbows, knees, scalp, and lower back. The skin cells in affected areas multiply much faster than normal, causing the characteristic buildup of patches. The condition tends to go through cycles of flaring and remission.