Decay‐accelerating factor (DAF), a GPI‐anchored regulator, is not expressed in the labyrinthine placenta until after ~10.5 dpc.13 Other C3 regulators of complement such as FH are present in maternal blood but they are unable to compensate for Crry deficiency. Here, CD55 is linked to hyperinsulinemic hypoglycemia, familial, 4.