A fertility supplement shows promise in helping women who have difficulty conceiving, according to a small pilot study from Stanford University School of Medicine.The study of 30 women found that, of those who took a supplement called FertilityBlend, a third became pregnant after five months. The findings appear in the April issue of the Journal of Reproductive Medicine.The FertilityBlend supplement contains chasteberry. This herb has been shown to improve ovulation and restore progesterone balance, which can be out of kilter in women who are having trouble conceiving. The supplement also contains L-arginine (an amino acid that improves circulation to the reproductive organs), green tea and a blend of vitamins and minerals, the researchers said.