Newborn · Preterm Risk
CRIB II — Very Preterm Baby Mortality Score
CRIB II clinical risk index for very preterm babies (<32 weeks or <1500 g). 5 items from admission data. Predicts mortality + morbidity. Used for benchmarking NICUs + informing parents. Parry et al. 2003.
Last reviewed 2 June 2026
CRIB-II — neonatal mortality risk
NICU benchmarking — preterm infants
g
wk
Sex
°C
mmol/L
Enter all 5 inputs to compute CRIB-II.
Educational tool only — not medical advice. CRIB-II (Parry 2003) is a 5-item score within 1 hour of NICU admission. Validated in BAPM benchmarking and European NICU networks. AUC ~0.91 for in-hospital mortality. Used for RISK-ADJUSTED unit comparison, NOT individual prognosis — many infants with high scores survive with intensive care.
What does this mean?
CRIB-II (Parry 2003) is one of the most widely-used risk- adjustment tools in neonatal benchmarking. It captures 5 things in the first hour of NICU admission (birth weight, GA, sex, admission temperature, base excess) and predicts in- hospital mortality with AUC ~0.91 for very preterm infants. The real purpose is unit-level comparison: NICU A and NICU B can compare their mortality rates fairly only after adjusting for how sick their admissions were on arrival. Used in BAPM benchmarking, the EuroNeoStat / EPICure networks. It is NOT an individual prognosis tool — many infants with high scores survive with modern intensive care, and modern 24–25-wk outcomes have improved substantially since the score was developed. Admission temperature is one of the easiest things to fix (warm transport, thermal mattress, plastic bag for ≤ 32 wk) and one of the strongest predictors of survival.
What is CRIB II?
Clinical Risk Index for Babies II — score predicting mortality + morbidity for very preterm babies (<32 weeks OR <1500 g birth weight). Parry et al. 2003 (UK + Ireland data).
The 5 items
- Sex.
- Birth weight.
- Gestation.
- Admission temperature.
- Base excess (acid-base balance).
Uses admission-only data (reduces bias from intervention variability).
What it predicts
- In-hospital mortality (best validated).
- Some morbidity outcomes (IVH, BPD, severe complications).
- Population-level risk; not individual death prediction.
Why admission temperature matters
Hypothermia (<36.5°C) at admission strongly associated with worse outcomes: mortality, intracranial haemorrhage, hypoglycaemia, infection. Preterm babies very vulnerable.
Protective measures: plastic bag/wrap (extreme preterm); hat; warm room; warmed gases; transport incubator.
Base excess
Severely negative base excess (<-7) indicates metabolic acidosis — inadequate oxygen delivery to tissues. Associated with brain injury, multi-organ stress, worse outcomes.
UK preterm survival (2020s NICU)
- 22 wk: ~30-40%.
- 23 wk: ~60-70%.
- 24 wk: ~75-85%.
- 25 wk: ~85-90%.
- 26 wk: ~90%.
- 27-28 wk: ~95%.
- 29-31 wk: >97%.
Neurodevelopmental outcomes
- 24-25 wk severe disability: ~25-35%.
- 26+ wk: ~10-20%.
- 28+ wk: smaller still.
Individual outcomes vary widely.
Possible lasting effects
- Respiratory: BPD (chronic lung disease); home oxygen, inhalers.
- Neurological: cerebral palsy, cognitive delays.
- Sensory: vision (ROP), hearing.
- Growth issues sometimes.
- Behavioural / attention concerns.
Majority of preterm babies live normal lives with early intervention support.
How CRIB II is used
- Research + NICU benchmarking.
- Parent counselling (population risk).
- Not deterministic for individual outcomes.
- Combined with clinical exam, imaging, family preferences.
Support for families
- NICU multidisciplinary team.
- BLISS UK (premature/sick babies).
- Family rooms.
- Breastfeeding support.
- Perinatal psychology.
- Peer support.
- Discharge planning + community follow-up.
Different scenarios
Scenario 1: 28-wk preterm, birth weight 1.1 kg, CRIB II 6
Moderate risk. Standard NICU intensive care. ~90% survival typically. Good outcomes likely with care.
Scenario 2: 23-wk preterm, very low birth weight, CRIB II 16
High risk. Multidisciplinary discussion with family about treatment intensity. Active care given but ethical discussion.
Scenario 3: 31-wk preterm, normal temp + base excess, CRIB II 2
Low risk. Standard care. Survival >95%. Likely good outcomes.
Scenario 4: 25-wk preterm, hypothermic on admission
Adds risk. Active rewarming. Thermal care emphasis.
Scenario 5: Very preterm survivor at 18 months, mild motor delay
Within expected range. Physio + developmental tracking. Outcomes improve over years.
Care guidance — very preterm care
- Antenatal steroids before preterm delivery.
- Magnesium sulphate <32 wk.
- Delayed cord clamping.
- Plastic bag / wrap to prevent hypothermia.
- Early surfactant if RDS.
- CPAP first-line where possible.
- Express breast milk from birth.
- BLISS UK family support.
- Long-term developmental follow-up.
Sources
- Parry G, et al. CRIB II: an update of the clinical risk index for babies score. Lancet 2003.
- BAPM. Perinatal management of extreme preterm birth (2019).
- Nuffield Council on Bioethics. Critical care decisions in fetal and neonatal medicine.
- BLISS UK. bliss.org.uk.
Recommended for this calculator
Frequently asked questions
What is CRIB II?
CLINICAL RISK INDEX FOR BABIES II — score predicting MORTALITY + MORBIDITY for very preterm babies (<32 weeks OR <1500 g birth weight). DEVELOPED Parry et al. 2003 (UK + Republic of Ireland data). 5 ITEMS: SEX, BIRTH WEIGHT, GESTATION, ADMISSION TEMPERATURE, BASE EXCESS. SIMPLER + more current than original CRIB (1993). USED for: RESEARCH (comparing NICU outcomes); BENCHMARKING units; INFORMING parents about prognosis; STRATIFYING by risk level.
What does CRIB II predict?
(1) IN-HOSPITAL MORTALITY in very preterm babies (best validated); (2) Some morbidity outcomes — IVH (intraventricular haemorrhage), BPD (bronchopulmonary dysplasia), severe complications. SCORE 0+ ; HIGHER = HIGHER risk. NOT a death prediction for individual baby — population-level risk; counsels parents about chances; informs intensity of care. EVERY baby individual + outcomes vary considerably.
Why was CRIB updated?
ORIGINAL CRIB (1993) included DAY 1 measurements + interventions. CRIB II (2003) uses ADMISSION-only data — REDUCES bias from intervention quality + variability between units; more useful for COMPARING outcomes across units. SIMPLER + faster to calculate. PROVES PROGNOSTIC factors largely set by birth not first day care quality. MOST UK NICUs use CRIB II for outcome reporting.
What are alternative scores?
(1) CRIB / CRIB II — UK + Ireland; (2) SNAP / SNAP-II / SNAPPE-II — Score for Neonatal Acute Physiology / Perinatal Extension; US developed; uses first 12 hours of physiological data; widely used research; (3) NEONATAL MORTALITY PREDICTION based on regional registries; (4) BIRTHWEIGHT-AGE charts (e.g. Fenton). EACH has strengths; UK practice + research uses CRIB II commonly.
What's a typical CRIB II score range?
0-23+ possible. EXAMPLES (approximate): MILD: CRIB II 0-5 — relatively low risk of death; (2) MODERATE: 5-10 — moderate risk; (3) HIGH: 10-15 — significant risk; (4) VERY HIGH: 15+ — high mortality risk + severe morbidity likely. EXTREME PRETERM (<26 wk) + low birth weight + temperature instability + acidosis → high scores. EVERY baby individual; score informs but doesn't determine.
Why is admission temperature so important?
HYPOTHERMIA (<36.5°C) at admission: STRONGLY ASSOCIATED with worse outcomes — increased mortality, intracranial haemorrhage, hypoglycaemia, infection. PRETERM babies VERY VULNERABLE: large body surface area:volume; immature thermoregulation; lose heat fast. PROTECTIVE MEASURES at birth: plastic bag/wrap (extreme preterm); hat; warm room; warmed gases; transport incubator. THERMAL CARE bundle implementation REDUCES early mortality.
What's base excess?
BLOOD GAS MEASUREMENT reflecting ACID-BASE balance. SEVERELY NEGATIVE base excess (e.g. <-7): METABOLIC ACIDOSIS — sign of inadequate oxygen delivery to tissues (hypoxia, poor perfusion, shock). PRETERM babies often have some acidosis at admission. SEVERE acidosis associated with: brain injury, multi-organ stress, worse outcomes. CORRECTING UNDERLYING cause (oxygen, fluids, blood pressure support, infection treatment) priority.
How is CRIB II used in counselling?
INFORMS PARENT DISCUSSIONS about prognosis WITHOUT being deterministic. SHARED DECISION-MAKING about intensity of care + escalation. CASE-BY-CASE: combined with clinical examination, imaging (ultrasound, MRI), parental preferences. ETHICAL frameworks (Nuffield 2006; BAPM consensus) guide decisions especially extreme preterm (22-24 wk) where outcomes vary widely. NO ONE SCORE determines outcome.
Does CRIB II affect treatment intensity?
INDIRECTLY. Very high score: extra vigilance + interventions; sometimes discussion about treatment ceiling if severely poor prognosis. NOT about WITHHOLDING care from individual babies who could benefit — about INFORMED FAMILY DISCUSSIONS. MODERN NICUs treat extreme preterm babies who would have been considered non-viable 20 years ago. EVERY baby gets full active care unless evidence + family discussion suggests palliative.
What's the prognosis for very preterm babies?
Approximate UK survival rates (2020s NICU): (1) 22 wk: ~30-40%; (2) 23 wk: ~60-70%; (3) 24 wk: ~75-85%; (4) 25 wk: ~85-90%; (5) 26 wk: ~90%; (6) 27-28 wk: ~95%; (7) 29-31 wk: >97%. NEURODEVELOPMENTAL outcomes: varies. SEVERE disability at 24-25 wk ~25-35%; 26+ wk ~10-20%; 28+ wk smaller still. INDIVIDUAL CASE depends on many factors.
Will my baby have lasting effects?
VARIABLE. POTENTIAL: (1) RESPIRATORY: BPD (chronic lung disease) — may need home oxygen, inhalers; (2) NEUROLOGICAL: cerebral palsy, cognitive delays, learning difficulties (more in extreme preterm); (3) SENSORY: vision (ROP), hearing; (4) GROWTH issues sometimes; (5) BEHAVIOURAL / ATTENTION concerns. MAJORITY of preterm babies live normal lives. EARLY INTERVENTION (physio, OT, SALT) crucial. BLISS / TAMBA UK support invaluable.
What support is available?
(1) NICU MULTIDISCIPLINARY team: neonatologists, nurses, dietitians, physiotherapists, psychologists, social workers; (2) BLISS UK — premature/sick babies; bedside support, family rooms, photography, advocacy; (3) FAMILY rooms in many NICUs for parents to stay; (4) BREASTFEEDING + lactation support; (5) PARENT-INFANT mental health — perinatal psychology often available; (6) PEER SUPPORT — other NICU families; (7) DISCHARGE planning — neonatal community nurses, GP, developmental follow-up; (8) COMPENSATION schemes if medical events contributed.
How does this relate to other calculators on BumpBites?
Companion: /calculators/snappe-ii (alternative); /calculators/apgar-score; /calculators/silverman-andersen; /calculators/nrp-algorithm; /calculators/sarnat-hie; /calculators/fenton-growth; /calculators/antenatal-steroids; /calculators/neonatal-cooling; /calculators/eos-sepsis.