Intralipid can suppress natural killer cells that are known to be involve in repeated implantation failure and recurrent miscarriages.Intralipid is made of purified soybean oil, egg phospholipids, glycerol and water. It provides essential fatty acids, linoleic acid, omega- 3 and 6 fatty acids and alpha-linolenic acid. The effects of Intralipid in suppressing natural killer cell activity (NKa) were found to be comparable to intravenous immunoglobulin (IVIG) by laboratory experiments.We will study the effect of intralipid infusion on the pregnancy outcome of women aged 35-40 years with history of repeated implantation failure of miscarriage and who have positive peripheral blood natural killer cells