NPY and hydrops fetalis: Furthermore, using the SPSS macro PROCESS30 to analyze the total sample (adjusting for age and gender), NPY genotypes had a significant main effect on HF (B = 0.10, SE = 0.04, t = 2.45, p = 0.014) and a marginally significant effect on RMSSD (B = 0.04, SE = 0.02, t = 1.90, p = 0.058), but PSS scores were not.