PTGDR2 and hydrops fetalis: We identified significant alterations in the expression of mRNA related to the AA inflammatory pathway, such as arachidonate 5-lipoxygenase-activating protein (Alox5ap), prostaglandin E receptor 2 (Ptger2), and prostaglandin D receptor 2 (Ptgdr2), in the HF + AD groups compared with the AD group (Figure 4D).