Gentlemen, researching anti-TNFs and breastfeeding I came across a reference to a study I hadn't previously known of:
Villiger PM, Caliezi G, Cottin V, et al. Effects of TNF antagonists on sperm characteristics in patients with spondyloarthritis. Ann Rheum Dis 2010; 69:1842–1844.
This article found that anti-TNF treatment does not impair sperm quality in patients with spondyloarthritis. To the contrary, patients on anti-TNF therapy showed significantly better sperm motility and vitality than untreated patients.