Are there any causes besides genetics of developing scid?

SCID. None that have been discovered unless the newborn had a serious or severe cancer/leukemia requiring chemotherapy and radiation which wipes out the immune system. Additionally, certain diseases (itp, etc.) that require strong therapy (rituxan) can wipe out the immune system.
Yes. If you have received the diagnosis of genetic severe combined immunodeficiency, implying mutations in specific genes, then it is strictly genetic. If you have less defined deficiencies of t-cells (viral. Fungal defense) or b-cells/immunoglobulins (bacterial defense), these can be acquired (e.g., aids) or transient (e.g., hypoglobulinemias) due to chemicals, infections, or cancer.