Newborn · Preterm Growth
Fenton Growth Chart — Preterm Baby Growth
Preterm growth tracking 22-50 weeks corrected gestational age. Expected weight gain 15-20 g/kg/day; catch-up growth; fortified breast milk; when to switch to UK-WHO charts. Fenton 2013.
Last reviewed 2 June 2026
Fenton 2013 preterm growth chart
Preterm weight-for-PMA percentile
Sex
wk
kg
Enter PMA (22-50 weeks) and weight in kg.
Educational tool only — not medical advice. Fenton 2013 is the AAP / CPS / WHO-aligned preterm growth chart for 22-50 weeks PMA. Tracks to WHO 0-24 mo standards at 50 weeks PMA. The 2025 third-generation Fenton charts (Paed Perinat Epidemiol 2025) further refine the LMS values. This widget uses median values from the 2013 publication.
What does this mean?
For preterm babies the right comparator is postmenstrual age (PMA), not chronological age or term reference charts. The Fenton 2013 chart is the AAP/CPS preferred growth reference from 22–50 weeks PMA, smoothly transitioning to the WHO 0–24 mo standards. NICU goals for stable preterms aim for ~15–20 g/kg/day weight gain in the early growth phase, with target percentile tracking parallel to the in-utero curve. SGA (small for gestational age, < 10th pct at birth) and EUGR (extrauterine growth restriction — falling off the curve postnatally) are common and matter long- term: better neurodevelopmental outcomes correlate with quality of growth (lean mass, head circumference) more than raw weight gain. Use corrected age (chronological − weeks early) for at least the first 2 years when assessing developmental milestones too.
What is the Fenton growth chart?
Growth chart for preterm babies 22-50 weeks corrected gestational age. Tanis Fenton 2013. Plots weight, length, head circumference. Percentiles 3rd, 10th, 50th, 90th, 97th.
Used until ~50 weeks corrected; then switch to WHO / UK-WHO charts.
Why different for preterm?
Preterm bodies grow differently. Term WHO charts misleading. Fenton based on intrauterine data + early postnatal preterm observations.
Birth weight recovery
- Initial loss up to 10-15% in first week normal.
- Recover by day 10-21 typically.
- Very preterm (24-26 wk): 14-21 days.
- Aggressive early nutrition minimises loss.
Normal preterm weight gain
- 15-20 g/kg/day after regaining birth weight.
- 1.5 kg baby = ~25-30 g/day.
- Weekly: ~150-200 g for very preterm.
- Head circumference: 0.5-1 cm/wk.
- Length: 0.5-1 cm/wk.
Fortified breast milk
Very preterm need more protein + calories + minerals than breast milk alone. Human milk fortifier added (dried powder). Reduces NEC + sepsis vs formula. Sometimes continues post-discharge weeks.
Catch-up growth
Most preterm catch up by 2-3 years (weight/length); 1-2 years (head). Some extreme preterm don’t fully catch up. Excessive rapid catch-up linked to later metabolic risk; balance.
Z-scores
- Z-score -1: 16th percentile.
- Z-score -2: 2.3rd percentile (close monitoring).
- Change over time more useful than single value.
BPD (bronchopulmonary dysplasia)
Chronic lung disease of prematurity. Oxygen need at 36 weeks corrected. Affects growth: increased respiratory effort, caloric needs, reduced feeding tolerance. Higher-calorie feeds; close monitoring; RSV / flu protection.
Breastfeeding preterm
- Express colostrum + milk from birth (within 6h).
- Hospital pump every 2-3 hours.
- NG tube feeds initially.
- Transition to direct breast 32-36 wk corrected.
- Fortifier added if needed.
- Skin-to-skin supports supply + bonding.
Switch to UK-WHO chart
At 50 weeks corrected (10 wk post-term). Some units at 40 wk.
Continue corrected age for growth tracking until 2 years chronological.
Failure to thrive causes
- Inadequate intake.
- Increased needs (sepsis, BPD, surgery).
- Malabsorption.
- Metabolic issues.
- Anaemia.
- Social factors post-discharge.
Assessment: dietitian, paediatrician, specialty referrals.
Different scenarios
Scenario 1: 28-wk preterm, week 4, gaining 16 g/kg/day on fortified BM
Within target. Continue. Weekly weights + biweekly head circumference.
Scenario 2: Growth tracking on -2 z-score persistently
Review feeds; increase calories; investigate causes; dietitian.
Scenario 3: Catch-up growth at 1 year corrected, hitting 25th percentile
Excellent. Switch to UK-WHO chart (already done at 50 wk corrected). Standard health visitor.
Scenario 4: 32-wk preterm, on home oxygen for BPD, slow growth
Higher calorie feeds. Multidisciplinary follow-up. RSV protection.
Scenario 5: Oral aversion at 6 months corrected, on NG tube
SALT referral. Gradual oral feeding programme. Community feeding team.
Care guidance — preterm growth
- Fenton chart 22-50 wk corrected.
- Target 15-20 g/kg/day after birth weight regain.
- Fortified breast milk for very preterm.
- Z-score trajectory matters more than absolute.
- Switch to UK-WHO at 50 wk corrected.
- Corrected age to 2 years.
- BLISS UK parent support.
- Multidisciplinary follow-up for very preterm.
Sources
- Fenton TR, Kim JH. A systematic review and meta-analysis to revise the Fenton growth chart for preterm infants. BMC Pediatr 2013.
- BAPM. Optimising early nutrition and growth.
- WHO Growth Standards. Multi-centre growth reference 2006.
- BLISS UK. bliss.org.uk.
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Frequently asked questions
What is the Fenton growth chart?
GROWTH CHART for PRETERM BABIES from 22 to 50 weeks corrected gestational age. CREATED by Tanis Fenton (Canada); 2013 update widely used. PLOTS: weight, length, head circumference vs age. PERCENTILES: 3rd, 10th, 50th, 90th, 97th. APPROPRIATE — preterm babies grow differently than term; using term WHO charts misleading. PRETERM in NICU + after discharge until ~50 wk (10 wk post-term) usually charted on Fenton; THEN switch to WHO/UK-WHO charts (≥40 weeks).
Why do preterm babies need different growth charts?
(1) PRETERM bodies grow in patterns DIFFERENT from in-utero; (2) USED TO BE CHARTED on intrauterine charts (assumes baby still in womb); (3) INTRAUTERINE growth NOT matched in preterm — they LOSE weight first, then catch up; (4) FENTON BASED on combined intrauterine data + early postnatal observations of healthy preterm. APPROPRIATE EXPECTATIONS reduce parent + clinical anxiety from inappropriate comparisons. PROMPTS interventions when growth genuinely deviating.
How is growth assessed?
MEASURED: (1) WEIGHT — daily on neonatal scale; weekly thereafter; (2) LENGTH — supine lying length-board; weekly; (3) HEAD CIRCUMFERENCE — weekly using non-stretch tape. RECORDED on Fenton chart. ASSESSED: tracks growth velocity (g/day OR g/kg/day). NORMAL PRETERM velocity: 15-20 g/kg/day post-initial loss. FAILURE to track adequately: review feeds, illness, possible underlying issue.
When do preterm babies regain birth weight?
TYPICALLY by DAY 10-21 after birth. INITIAL WEIGHT LOSS normal — fluid shifts, urine, meconium. ACCEPTABLE LOSS: up to 10-15% of birth weight in first week. SLOWER recovery in preterm than term — extremely preterm (24-26 wk) may take 14-21 days. AGGRESSIVE early nutrition (TPN initially, gradual enteral feeds) helps minimise loss. SUPPORTED with mother's milk + fortified feeds.
What's normal preterm weight gain?
AIM: 15-20 g/KG/DAY (after regaining birth weight). EXAMPLE: 1.5 kg baby = ~25-30 g/day. WEEKLY: ~150-200 g/wk for very preterm. INCREASES with maturity. POST-DISCHARGE: continue weekly weights initially; transition to standard growth tracking. HEAD GROWTH important: target 0.5-1 cm/wk (slows after 10 wk). LENGTH: 0.5-1 cm/wk.
What about catch-up growth?
CATCH-UP varies: most preterm babies catch up to standard percentiles by 2-3 YEARS for weight/length; head circumference often by 1-2 years. SOME never fully catch up (especially extreme preterm). LATER catch-up: especially in early childhood + puberty. EXCESSIVE catch-up (large rapid gains): some evidence of metabolic risk later — balance. NORMAL pattern: gradual approach to centile that fits child's genetic potential.
Why feed fortified breast milk?
BREAST MILK is gold standard nutrition but VERY PRETERM babies need more PROTEIN + CALORIES + MINERALS than breast milk alone provides for optimal growth. HUMAN MILK FORTIFIER added — typically dried powder mixed into expressed breast milk; provides extra protein, minerals (calcium, phosphate, vitamins). USED in NICU for very preterm (<32-34 wk) often. SOMETIMES continues post-discharge for several weeks. MOTHER'S MILK reduces NEC + sepsis vs formula.
What's failure to thrive in preterm?
GROWTH not tracking expected curve. CAUSES: (1) INADEQUATE intake (feeding tolerance, ROP/eye issues affecting feeding, oral aversion); (2) INCREASED needs (sepsis, BPD lungs, surgery recovery); (3) MALABSORPTION; (4) METABOLIC issues; (5) ANAEMIA; (6) SOCIAL factors (post-discharge). ASSESSMENT: dietitian, paediatrician, sometimes specialty referral. EXTRA fortification, change feeds, address underlying cause. SOMETIMES tube feeds (NG, gastrostomy) needed for prolonged poor feeding.
What's BPD and how does it affect growth?
BRONCHOPULMONARY DYSPLASIA — chronic lung disease of prematurity. CAUSES: prolonged oxygen + ventilation in extreme preterm. SIGNS: oxygen need at 36 weeks corrected age. AFFECTS GROWTH: increased respiratory effort + caloric needs; reduced feeding tolerance (breathlessness with feeds); may need supplemental oxygen home. NUTRITION: higher calorie feeds; close growth monitoring; flu / RSV protection winter; multidisciplinary care. MOST IMPROVE through childhood.
Can I breastfeed a preterm baby?
YES — strongly encouraged. EVERY preterm baby benefits. (1) EXPRESS COLOSTRUM + milk from birth (within 6 hours); (2) HOSPITAL pump every 2-3 hours; (3) MILK given via NG tube initially; (4) GRADUAL transition to direct breastfeeding as baby matures (32-36 weeks corrected typical readiness); (5) FORTIFIER added if needed; (6) SKIN-TO-SKIN supports milk production + bonding. SOMETIMES top-up bottles needed. LACTATION CONSULTANT support essential. POST-DISCHARGE: continue breastfeeding ideally.
What's z-score / SDS?
STATISTICAL measure of how a measurement compares to reference. Z-SCORE (or SDS = Standard Deviation Score): -1 = 16th percentile; -2 = 2.3rd percentile; +1 = 84th percentile; etc. USED in preterm growth tracking. Z-SCORE OF -1 OR LESS: below 10-15th percentile — close monitoring. -2 OR LOWER: significant growth issue. CHANGE in z-score over time (positive = catching up; negative = falling further) more useful than single value.
When do we stop using Fenton chart?
AT 50 WEEKS corrected (10 weeks post-term equivalent), switch to WHO / UK-WHO charts. SOME UNITS earlier (at 40 weeks term-equivalent). CONTINUE using CORRECTED AGE for growth assessment until 2 YEARS chronological age (preterm babies normalise developmentally by then). CONSISTENCY important — same chart for trajectory tracking. PARENT-HELD records (red book UK) often used post-discharge.
Will my preterm baby be small adult?
MOST CATCH UP. EXTREME PRETERM (<28 wk): slightly higher rates of shorter adult height (mean 1-2 cm shorter). VERY LOW BIRTH WEIGHT or severe IUGR: more pronounced. EARLY GROWTH RESTRICTION: more long-term impact than late. METABOLIC PROFILE: small increase in adult diabetes, hypertension risk in extreme preterm. HEALTHY LIFESTYLE protective. MOST PRETERM CHILDREN lead normal adult lives.
What about feeding difficulties at home?
(1) ORAL AVERSION — some preterm babies, especially those with prolonged tube feeds; SALT (speech and language therapy) help with feeding development. (2) REFLUX common in preterm — anti-reflux measures, sometimes medication. (3) FEEDING TUBE at home (NG, gastrostomy) — some need long-term; community team support. (4) FORTIFIED FORMULA or breast milk options. (5) NUTRITION TEAM follow-up. (6) BLISS / Tinies (UK) parent support.
How does this relate to other calculators on BumpBites?
Companion: /calculators/baby-percentile (WHO/UK-WHO for term); /calculators/baby-age (corrected age); /calculators/new-ballard; /calculators/breastfeeding-latch; /calculators/newt-weight-loss; /calculators/antenatal-steroids; /calculators/silverman-andersen; /calculators/eos-sepsis.