Why is Beyfortis (Vitamin K) given to newborns?

Why Beyfortis Must Be Given to Newborns

I believe there is a critical misunderstanding in your question: Beyfortis is NOT Vitamin K—it is nirsevimab, a monoclonal antibody for RSV prevention. However, I will answer about Vitamin K prophylaxis in newborns, which appears to be what you're asking about based on the expanded question context.

The Critical Need for Vitamin K at Birth

All newborns should receive vitamin K prophylaxis within one hour of birth to prevent life-threatening vitamin K deficiency bleeding (VKDB), with intramuscular administration being the gold standard and most reliable method. 1

Why Newborns Are at Risk

• Newborns have physiologically decreased plasma levels of vitamin K-dependent coagulation factors (factors II, VII, IX, and X) compared to adults, making them inherently vulnerable to bleeding disorders 2
• Breast milk contains extremely low concentrations of vitamin K, making exclusively breastfed infants particularly susceptible to deficiency 2
• Poor placental transfer of vitamin K during pregnancy leaves infants with insufficient stores at birth 3
• Immature gut flora and poor intestinal absorption prevent adequate vitamin K synthesis in the newborn period 3

Types of Bleeding Without Prophylaxis

VKDB occurs in three distinct patterns without prophylaxis: 3, 4

• Early VKDB: Within 24 hours of birth (often related to maternal medications)
• Classic VKDB: Within the first week after birth
• Late VKDB: Between 2 weeks and 6 months of age—this is the most dangerous form, with up to half of affected infants experiencing intracranial hemorrhage 5

The Gold Standard: Intramuscular Administration

The American Academy of Pediatrics recommends a single intramuscular dose of 0.5 to 1.0 mg vitamin K1 within one hour of birth as the most effective route for preventing all forms of VKDB. 1

• This single IM injection effectively prevents both classic and late VKDB 5
• IM administration is more reliable than oral routes because it doesn't depend on intestinal absorption or parental compliance 6
• The dose must be documented, including date, dose, and mode of administration 6

Alternative Oral Regimens (Less Effective)

If parents refuse IM administration after adequate counseling, oral alternatives exist but require multiple doses and strict compliance: 1, 6

• Option 1: 2 mg at birth, 2 mg at 4-6 days, and 2 mg at 4-6 weeks 1
• Option 2: 2 mg at birth, then weekly 1 mg doses for 3 months (12 weeks total) 1
• Critical limitation: Oral prophylaxis is less effective than IM for preventing late VKDB, particularly in infants with undiagnosed cholestasis or malabsorption 6

High-Risk Populations Requiring IM/IV Route

The oral route is NOT appropriate for: 6

• Preterm infants (who require 10 μg/kg/day on parenteral nutrition) 2, 1
• Newborns with cholestasis or impaired intestinal absorption 6
• Infants whose mothers took medications interfering with vitamin K metabolism (anticonvulsants, anticoagulants, antituberculosis drugs) 2
• Infants with cystic fibrosis, alpha-1-antitrypsin deficiency, or biliary disease 2

Safety Profile

Vitamin K1 (phylloquinone) is considered safe with no known adverse effects of supplementation. 2, 1

• The disproven cancer concern: An association with childhood cancer has been thoroughly debunked, yet parental refusal persists based on this misinformation 5
• Prompt diagnostic response: Shortening of prothrombin time within 2-4 hours following vitamin K administration confirms VKDB diagnosis 1

Common Pitfalls to Avoid

• Do not skip prophylaxis in formula-fed infants—while formula is supplemented with vitamin K, the initial dose at birth is still essential 7
• Document parental refusal if parents decline after adequate counseling, as this creates significant medicolegal and clinical risk 6
• Repeat the oral dose if the infant vomits or regurgitates within 1 hour of administration 6
• Recognize warning signs of late VKDB: jaundice, failure to thrive, feeding problems, minor bleeding, or cholestatic diseases 4