Semaphorin-4D (SEMA4D; also known as CD100) is a key gene in the top HF vs C pathway, “Semaphorin Signaling in Neurons”, was significantly up-regulated in HF vs C. Interestingly, Zhang et al. 26 recently showed that SEMA4D promotes inflammation by activating the NF-kB and inflammasome pathways in keratinocytes. Here, SEMA4D is linked to hydrops fetalis.