Maternal contamination at fetal muscle biopsy

Duchenne muscular dystrophy (DMD) can be diagnosed by fetal muscle biopsy and immunohistochemical staining showing the absence of dystrophin. We report a case of fetal muscle biopsy in which the needle gun was successfully fired within the fetal gluteal muscle but the sample was contaminated by maternal tissue. This was attributed to the design of the biopsy needle, allowing transient opening of the biopsy core as the needle penetrated the maternal rectus sheath, muscle, and myometrium. Histology showed tissue suggestive of maternal origin, confirmed by DNA analysis. Repeat sampling revealed fetal muscle with normal dystrophin expression. We recommend that care be taken during needle insertion to avoid maternal contamination, and tests be used to confirm the fetal source of the sample.