PLE-1550

A neonate is admitted to the intensive neonatal care and incubated due to jaundice. He was born to a 30-year-old G3P2 who is known to be Rh-negative, with an Rh-positive sexual partner. The mother has not received anti-D prophylaxis during the current pregnancy. You suspect Rh incompatibility. Which of the following serum proteins is expected to be decreased in the neonate?