When should a coagulation profile be ordered and vitamin K (phylloquinone) administered for a newborn (neonate)?

Neonatal Coagulation Profile and Vitamin K Administration

Vitamin K Prophylaxis Timing

All healthy newborns should receive vitamin K1 0.5 to 1 mg intramuscularly within one hour of birth. 1

• The American Academy of Pediatrics recommends this single intramuscular dose as standard prophylaxis against hemorrhagic disease of the newborn 1
• This prevents vitamin K deficiency bleeding (VKDB), which can occur because neonates have limited vitamin K stores and reduced levels of vitamin K-dependent clotting factors (II, VII, IX, X) at birth—approximately 50% of adult values 2
• Oral vitamin K is an alternative for healthy full-term babies who are orally fed, though the intramuscular route provides more reliable absorption 2

Special Populations Requiring Parenteral Administration

• Small preterm infants and sick full-term babies should receive parenteral (intramuscular) vitamin K rather than oral administration 2
• Infants born to mothers on enzyme-inducing drugs (anticonvulsants, rifampin, isoniazid) require maternal vitamin K supplementation during the last 15-30 days of pregnancy, plus standard neonatal prophylaxis 2

When to Order Coagulation Studies

Do NOT routinely order coagulation profiles on healthy newborns receiving standard vitamin K prophylaxis

Order coagulation studies (PT, aPTT, fibrinogen) in neonates only when specific clinical indications are present:

• Active bleeding (umbilical stump, gastrointestinal, intracranial, or other sites) 1, 3
• Suspected hemorrhagic disease of the newborn despite vitamin K prophylaxis 1
• Maternal history of anticoagulant use during pregnancy 1
• Clinical presentation suggesting homozygous protein C deficiency (purpura fulminans, extensive thrombosis) 4, 5
• Planned invasive procedures in high-risk infants 3
• Family history of bleeding disorders 3

Interpreting Neonatal Coagulation Studies

Normal neonatal coagulation values differ significantly from adults and vary by postnatal age 6:

• Day 0-3: PT is prolonged (mean ~54% of adult values), aPTT is moderately prolonged (mean 44 seconds), fibrinogen is typically normal 7, 6
• Day 4-6: PT normalizes in infants who received vitamin K prophylaxis 7
• Day 7-10: PT reaches adult reference range; aPTT remains slightly elevated 6
• Day 11-20: aPTT may still be above adult upper limit in 71% of infants 6

Critical pitfall: Do not use adult reference ranges for neonatal coagulation tests—this leads to false-positive results in up to 94% of healthy newborns on day 0 for PT and 71% at day 11-20 for aPTT 6

Treatment of Hemorrhagic Disease of the Newborn

If a neonate presents with bleeding despite prophylaxis or before prophylaxis was given:

1. Administer vitamin K1 1 mg subcutaneously or intramuscularly immediately 1
2. If bleeding is severe or infant is in shock, give fresh frozen plasma (FFP) 10-20 mL/kg to provide immediate clotting factors while waiting for vitamin K to take effect (2-4 hours for response) 5, 1
3. Recheck PT in 2-4 hours: A prompt shortening of PT is diagnostic of vitamin K deficiency bleeding; failure to respond indicates another coagulation disorder 1
4. Higher vitamin K doses may be necessary if the mother received oral anticoagulants 1
5. Consider whole blood or component therapy if bleeding is excessive, but this does not correct the underlying disorder—vitamin K must still be given concurrently 1

Rare but Critical Differential: Homozygous Protein C Deficiency

If a neonate presents with purpura fulminans or extensive thrombosis (not typical bleeding):

• Administer FFP 10-20 mL/kg every 12 hours OR protein C concentrate 20-60 units/kg until clinical lesions resolve (Grade 1A recommendation) 4, 5
• After stabilization, long-term treatment options include vitamin K antagonists, LMWH, protein C replacement, or liver transplantation 4