Skipping newborn vitamin K tied to 47% higher bleeding risk in US infants

A Children’s Hospital of Philadelphia analysis published in JAMA on 5 November 2026 links declining newborn intramuscular vitamin K shots to higher infant bleeding risk.

Study type and cohort

• Type: retrospective observational cohort using Epic Cosmos electronic health records (not a randomised trial).
• Population: 5,240,780 US infants born at 35–43 weeks (2017–2025), followed through six months; 234,825 (4.5%) had no documented intramuscular vitamin K.
• Nonreceipt rose from 3.1% in 2017 to 6.8% in 2025.

Main findings

After adjustment for gestational age, sex, maternal factors, insurance and neighbourhood measures:

• Any recorded bleeding by six months: 288 vs 186 per 10,000 births (nonreceipt vs receipt); adjusted risk ratio 1.47 (95% CI 1.43–1.51) — about 47% higher risk.
• Intracranial bleeding: 33.0 vs 13.2 per 10,000; ARR 2.43.
• Death with concurrent bleeding during the birth hospitalisation: ARR 2.69.
• Estimated number needed to harm ≈ 114 (one extra bleeding event per 114 newborns without the shot).

Lead author Kristan Scott and co-authors say the findings reinforce the longstanding recommendation for a one-time intramuscular vitamin K injection shortly after birth.

Limitations

Observational design cannot prove causation. The study excluded preterm births before 35 weeks and likely undercounted home/birth-centre births; oral or delayed vitamin K could not be fully distinguished; coding differences might inflate bleeding when vitamin K was declined. Talk to your doctor about newborn vitamin K decisions.