A natural killer cell subset that is found in the decidual of the uterus and is CD56-high, Galectin-1-positive and CD16-negative. This cell type represents the most abundant immune cell type in the decidual during the first trimester of pregnancy. [ http://www.ncbi.nlm.nih.gov/pubmed/14568979 http://www.ncbi.nlm.nih.gov/pubmed/19800965 ]