Newborn · Severity Score
SNAPPE-II — Newborn Severity Score
Score for Neonatal Acute Physiology with Perinatal Extension. 9 items from first 12 hours predict mortality + morbidity. Used for NICU benchmarking + research. Richardson 2001.
Last reviewed 2 June 2026
SNAPPE-II — neonatal mortality risk
NICU 12-hour acute physiology + perinatal extension
mmHg
°C
pH
mL/kg/h
g
/10
Seizures in first 12h
Enter at least the 7 key physiological / perinatal values.
Educational tool only — not medical advice. SNAPPE-II (Richardson 2001) is the most-used NICU severity score in the US (Vermont Oxford Network). AUC 0.91 for in-hospital mortality (validated in 14,610 admissions). Used for risk-adjusted unit benchmarking, NOT individual prognosis — many infants with high scores survive with intensive care.
What does this mean?
SNAPPE-II (Richardson 2001) combines 9 physiology and perinatal items from the first 12 hours of NICU admission into a single 0–162 score. Like CRIB-II in Europe, it’s the standard risk-adjustment tool in US NICUs (Vermont Oxford Network). AUC ~0.91 for in-hospital mortality (validated in 14,610 admissions). The components capture cardiovascular (lowest MAP), respiratory (PaO2/FiO2), metabolic (pH), neurological (seizures), renal (urine output), thermal (temperature) and perinatal (birth weight, SGA status, Apgar) compromise. The point of this score is fair unit-vs-unit comparison — not parent-facing prognosis. Modern outcomes have improved substantially since development, and individual prognosis depends on many downstream factors not captured here (NEC, IVH, ROP, BPD, surgical events).
What is SNAPPE-II?
Score for Neonatal Acute Physiology with Perinatal Extension Version II. 9-item illness severity score from first 12 hours. Predicts mortality. Richardson et al. 2001.
The 9 items
Physiology (first 12h):
- Mean blood pressure.
- Temperature.
- PO2/FiO2 ratio.
- Lowest serum pH.
- Multiple seizures.
- Urine output.
Perinatal extension:
- Birth weight.
- Small for gestational age.
- APGAR (5 min).
Score interpretation
- 0-20: relatively well; low mortality risk.
- 20-40: moderate illness; moderate risk.
- 40+: severe illness; high risk.
Population-level risk; individual outcomes vary.
SNAPPE-II vs CRIB II
- CRIB II: 5 items, admission-only; UK / Ireland.
- SNAPPE-II: 9 items, first 12h; US.
Both validated; similar accuracy. SNAPPE-II adds first 12h information.
Key parameters explained
- Multiple seizures: HIE, haemorrhage, sepsis, meningitis, metabolic causes.
- Urine output >1 mL/kg/h after 24h normal; <0.5 = AKI / poor perfusion.
- PO2/FiO2 ratio: oxygenation index; <200 severe hypoxaemia.
- Temperature: hypothermia (<36.5°C) bad prognostic.
Does it affect treatment?
Directly rarely. Informs parent counselling, research, NICU benchmarking. NICU care individualised; all babies get optimal active care. Very high scores prompt earlier multidisciplinary discussions about futility / palliative only after extensive treatment.
Accuracy
AUC for mortality ~0.85-0.90 — better than gestation alone (~0.75). Where care has improved, mortality for any score lower than original validation cohort.
Long-term outcomes
Depend on diagnoses, neuroimaging, recovery trajectory, postnatal interventions, family environment, socioeconomic factors. Developmental follow-up 3, 6, 12, 24 months + ongoing.
Different scenarios
Scenario 1: 28-wk preterm, no acidosis, no seizures, SNAPPE-II 15
Mild-moderate illness. Standard NICU care. Good prognosis usually.
Scenario 2: Term baby, HIE, SNAPPE-II 35
Moderate-severe. Cooling. Intensive care. Multidisciplinary follow-up.
Scenario 3: 24-wk preterm, very low BW, hypothermic, SNAPPE-II 50
Severe. Family meeting about prognosis. Active care given.
Scenario 4: Low score but baby deteriorating
Investigate clinically; score is snapshot. New events change picture.
Scenario 5: High score but baby surprises everyone
Population scores don’t determine individual outcomes. Individual care continues.
Care guidance — severity scoring
- Scores inform but don’t determine.
- Individual care continues regardless.
- Family meetings + shared decisions.
- Combined with imaging + clinical exam.
- BLISS UK family support.
- Long-term developmental follow-up.
- Outcomes improving over time with NICU advances.
Sources
- Richardson DK, et al. SNAP-II and SNAPPE-II: simplified newborn illness severity and mortality risk scores. J Pediatr 2001.
- BAPM. Perinatal management of extreme preterm birth.
- BLISS UK. bliss.org.uk.
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Frequently asked questions
What is SNAPPE-II?
SCORE FOR NEONATAL ACUTE PHYSIOLOGY WITH PERINATAL EXTENSION VERSION II. SIMPLIFIED illness severity score for newborns. Created by Richardson et al. 2001 (Journal of Pediatrics). 9 ITEMS: from first 12 HOURS of life. PREDICTS in-hospital mortality. WIDELY USED globally for research + benchmarking. ALTERNATIVE to CRIB II (UK preference). EITHER score reasonable; protocols vary by unit.
What are the 9 SNAPPE-II items?
FIRST 12 HOURS: (1) MEAN BLOOD PRESSURE; (2) TEMPERATURE; (3) PO2/FiO2 RATIO; (4) SERUM pH (lowest); (5) MULTIPLE SEIZURES; (6) URINE OUTPUT; PERINATAL EXTENSION: (7) BIRTH WEIGHT; (8) SMALL FOR GESTATIONAL AGE; (9) APGAR (5 min). EACH item scored 0+. TOTAL +ve score; HIGHER = sicker baby + worse prognosis. ENCAPSULATES first 12 hours intensity of illness.
What does the score mean?
SCORES 0+. EXAMPLES: (1) 0-20: relatively well; low mortality. (2) 20-40: moderate illness; moderate mortality risk. (3) 40+: severe illness; high mortality risk. POPULATION RISK; individual outcomes vary. CUT-OFFS differ by unit / population. USED for: comparing NICU outcomes; severity-adjusted mortality reports; research stratification; parent prognostic discussions.
Why first 12 hours?
CAPTURES INITIAL severity + early intervention response. EARLIEST window for prognostic information beyond birth weight + gestation. CRITICAL early-life parameters (BP, temperature, oxygenation, acidosis, seizures, urine output) reflect: birth process, transition adaptation, underlying illness severity. CRIB II uses admission-only data; SNAPPE-II adds first 12 hours; trade-off — SNAPPE-II more accurate but reflects care quality too.
How does SNAPPE-II differ from CRIB II?
(1) CRIB II: 5 items, admission-only data (sex, birth weight, gestation, temperature, base excess); simpler; UK + Ireland origin. (2) SNAPPE-II: 9 items, first 12 hours; more comprehensive; US origin. (3) BOTH validated; similar predictive accuracy in different populations. (4) CHOICE per unit + study. ROUTINE clinical use less common — research + outcomes reporting primary use.
What about seizures in the score?
MULTIPLE SEIZURES in first 12 hours adds significant points. CAUSES of neonatal seizures: HIE (commonest); intracranial haemorrhage; sepsis; meningitis; metabolic (hypoglycaemia, electrolyte disturbance); congenital brain anomalies; drug withdrawal; benign familial. MANAGEMENT: continuous EEG/aEEG monitoring; phenobarbital first-line; phenytoin / levetiracetam if not controlled. INVESTIGATIONS to find cause.
What does urine output indicate?
URINE OUTPUT in first 24 hours reflects: renal function; volume status; cardiovascular adequacy. NEONATE: target >1 mL/kg/hour after first 24h. <0.5 mL/kg/hour: acute kidney injury / poor perfusion. CAUSES: hypovolaemia; sepsis; HIE causing renal hypoperfusion; congenital renal anomalies; obstruction. MANAGEMENT: address cause; fluid management; sometimes ECMO / dialysis (extreme cases).
What about PO2/FiO2 ratio?
OXYGENATION INDEX measure. PaO2 (arterial oxygen partial pressure) ÷ FiO2 (fraction of inspired oxygen). NORMAL: >300 (well-oxygenated room air). MODERATE: 200-300. SEVERE hypoxaemia: <200. PEDIATRIC ARDS-like presentations. REQUIRES BLOOD GAS sampling. INFORMS ventilation strategy + escalation (e.g. high-frequency ventilation, ECMO consideration in severe cases).
Will the score affect my baby's treatment?
DIRECTLY rarely — but informs: (1) PARENT COUNSELLING; (2) RESEARCH outcomes adjustment; (3) UNIT BENCHMARKING. NICU CARE is INDIVIDUALISED to each baby; ALL get optimal active care regardless of admission score. SCORE doesn't WITHHOLD interventions. SOMETIMES very high scores prompt earlier multidisciplinary discussions about futility / palliative care — only after extensive treatment + clear evidence.
How accurate is SNAPPE-II?
GOOD prognostic accuracy in validation studies. AUC (area under curve) for mortality ~0.85-0.90 — better than gestation alone (~0.75). NOT 100% — individual babies surprise. CONTEXT MATTERS: scoring system validity depends on population studied + care quality. WHERE care has improved, MORTALITY for any score lower than original validation cohort.
What's the SNAP-II vs SNAPPE-II difference?
SNAP-II: 6 PHYSIOLOGY items only (BP, temp, PO2/FiO2, pH, seizures, urine output). SNAPPE-II: SNAP-II + 3 PERINATAL items (birth weight, SGA, APGAR). PERINATAL extension PROVIDES additional prognostic information. SNAPPE-II generally preferred for newborn populations. Both Richardson et al. 2001.
What if I want comprehensive prognosis info?
REQUEST family meeting with neonatology team. INFORMATION SHARED: (1) Diagnoses; (2) Risk factors; (3) Imaging findings (cranial ultrasound, MRI); (4) Severity scores (CRIB II / SNAPPE-II); (5) Expected trajectory; (6) Treatment plan + escalation; (7) DISCHARGE plan + follow-up. WRITE QUESTIONS ahead of meeting; bring partner/family. INFORMED CHOICES through shared decision-making.
What about my baby's long-term?
LONG-TERM OUTCOMES depend on many factors beyond admission scores: (1) ULTIMATE diagnoses; (2) NEUROIMAGING findings; (3) Recovery trajectory; (4) Postnatal interventions; (5) Family environment + early intervention; (6) Socioeconomic factors. DEVELOPMENTAL FOLLOW-UP at 3, 6, 12, 24 months + ongoing. MOST very preterm survivors thrive with appropriate support.
How does this relate to other calculators on BumpBites?
Companion: /calculators/crib-ii (UK alternative); /calculators/apgar-score; /calculators/silverman-andersen; /calculators/sarnat-hie; /calculators/nrp-algorithm; /calculators/fenton-growth; /calculators/eos-sepsis; /calculators/neonatal-cooling; /calculators/newborn-bilirubin.