For some years, a prevalent theory has been that predominant production of so-called T helper type 2 (Th2) cytokines such as interleukin (IL)-4 and IL-10 was characteristic of normal implantation and pregnancy, whereas in miscarriage, and recurrent miscarriage there was a predominant production of Thl cytokines such as IL-1 and IL-2 [14]. The gene discussed is IL4; the disease is spontaneous abortion.