Intralipid® is a fat emulsion and calorie source administered intravenously. Comprising soybean oil, egg yolk phospholipids, glycerine, and water, it helps downregulate natural killer (NK) cells, which can prevent an embryo from attaching to the uterine wall. A typical course of Intralipid® treatment during IVF is delivered in two doses: the first one seven to 10 days before egg retrieval; the second, on the day of transfer.