At birth, which vitamin is given intramuscularly to prevent hemorrhagic disease?

• A. Vitamin D
• B. Vitamin K
• C. Vitamin A
• D. Vitamin E

Answer: (B)

Vitamin K is given intramuscularly at birth to prevent hemorrhagic disease of the newborn. Newborns have very low vitamin K stores and their gut is sterile, so they don’t synthesize enough vitamin K for clotting factors. Vitamin K is required for the gamma-carboxylation of clotting factors II, VII, IX, and X (and proteins C and S); without it, these factors don’t function properly and bleeding can occur, including inside the skull. Giving vitamin K by the intramuscular route soon after birth ensures reliable, rapid absorption and protection against both early and late vitamin K deficiency bleeding. Other vitamins like D, A, and E are important for other health needs but do not prevent hemorrhagic disease.