Preterm Infant

Aka: Preterm Infant, Preterm Infant Outcomes, Premature Infant, Low Birth Weight Infant, Gestational Age, Chronological Age, Postnatal Age, Postmenstrual Age, Corrected Age

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II. Definitions: Preterm

  1. Early term
    1. Gestational Age 37 to <39 weeks
  2. Moderate to Late preterm
    1. Gestational Age 34 to <37 weeks
  3. Very preterm
    1. Gestational Age 28 to <34 weeks
  4. Extremely preterm
    1. Gestational Age <28 weeks
  5. Border of viability
    1. Gestational Age 22 to <25 weeks

III. Definitions: Weight

  1. Low birth weight
    1. Birth weight <2500 grams (5 pounds 8 ounces)
  2. Very low birth weight
    1. Birth weight <1500 grams (3 pounds 5 ounces)
  3. Extremely low birthweight
    1. Birth weight <1000 grams (2 pounds 3 ounces)

IV. Definitions: Age

  1. Gestational Age (GA)
    1. Time duration from LMP to delivery date
  2. Chronological Age (Postnatal Age)
    1. Time duration from delivery date (birth date)
  3. Postmenstrual Age
    1. Gestational Age plus Chronological Age
    2. Example: Preterm Infant born at 26 weeks (GA) and now 6 weeks after delivery (Chronological Age)
      1. Postmenstrual Age = 26 + 6 = 32 weeks
  4. Corrected Age
    1. Chronological Age minus weeks premature
    2. Example: For 26 week Premature Infant (14 weeks premature), now 6 months or 26 weeks after delivery
      1. Corrected Age = 26 - 14 = 12 weeks or 3 months

V. Epidemiology

  1. Incidence: 10% of all births are at gestation age <37 weeks (2023, U.S.)

VI. Complications

  1. Hypoxic-Ischemic Encephalopathy
  2. Periventricular leukomalacia
  3. Intraventricular Hemorrhage
  4. Retinopathy of Prematurity
  5. Bronchopulmonary Dysplasia
  6. Necrotizing Enterocolitis

VII. Associated Conditions: Comorbidity in Preterm Infants

  1. Chronic lung disease (e.g. Bronchopulmonary Dysplasia)
  2. Apnea of Prematurity
  3. Bradycardia
  4. Pediatric Gastroesophageal Reflux (earlier onset and more severe than in term infants)
  5. Cryptorchidism
  6. Hernia
  7. Developmental Delay
  8. Growth Delay
  9. Sudden Infant Death Syndrome
  10. Ventriculomegaly

VIII. Evaluation: Prior to NICU discharge

  1. Key NICU Discharge Components (AAP)
    1. Caregiver education
      1. Two Caregivers should demonstrate appropriate feeding and caring of infant prior to discharge
    2. Primary care implementation
      1. Provided comprehensive summary of neonatal course
    3. Unresolved medical problem evaluation
    4. Home care plan assessment
    5. Support service identification and mobilization
    6. Follow-up care determination and designation
      1. Clear follow-up instructions
  2. Care seat test
    1. Demonstrates that infant tolerates restraints without respiratory distress
    2. May require prone or supine care safety device as an alternative
  3. Cranial Ultrasound (for infants born before 30 weeks gestation)
    1. Screens for intraventricular Hemorrhage and periventricular leukomalacia
    2. Performed at 7-10 days of life and at 36-40 weeks adjusted age
  4. Retinopathy of Prematurity
    1. Preterm Infants at Risk: <30 weeks gestation, <1500 g birth weight
    2. Dilated Eye Exam by ophthalmologist in NICU before discharge for infants at risk
  5. Hearing Impairment
    1. Preterm Infants at Risk: <30 weeks gestation, <1500 g birth weight, >5 days in NICU
    2. Auditory Brainstem Response testing

IX. Evaluation: Outpatient Schedule

  1. Post-hospital discharge at 24-48 hours
    1. Review hospital course, medications and medical equipment
    2. Review urine and stool output
    3. Measure weight, length and Head Circumference
      1. Visit weight below NICU discharge weight warrants a repeat visit within 72-96 hours
      2. Obtain weekly or biweekly weight for the first 4-6 weeks after hospital discharge
    4. Repeat Newborn Exam
    5. Review subspecialty follow-up (typically aranged by NICU, see indications below)
    6. Review SIDS prevention
  2. Post-hospital discharge at 2-4 weeks
    1. Review medications and subspecialty monitored issues
    2. Review feeding history
      1. See Growth Assessment and management below
    3. Measure weight, length and Head Circumference
      1. Continue to obtain weekly or biweekly weight for the first 4-6 weeks after hospital discharge
      2. Plot Growth Parameters on premature growth chart for the first 24 months of life
      3. Expect catch-up to occur first with Head Circumference, then with length and then with weight
      4. Neurosurgery/Imaging evaluation for disproportionate head growth
        1. May reflect Hydrocephalus or Craniosynostosis
    4. Physical exam
    5. Iron Supplementation for Breastfed infants 1-2 mg/kg/day
      1. Formula contains the recommend 2 mg/kg/day iron (no additional iron needed in formula fed infants)
  3. Chronological Age 2 months, 4 months, 6 and 9-12 month visits
    1. Review medications and subspecialty monitored issues
    2. Review feeding history
      1. See Growth Assessment and management below
      2. Feeding fortification may be stopped when weight for age >25th percentile
      3. Complimentary foods may be introduced at 4-6 months Corrected Age
      4. Transition to whole milk at 12 months (same as term infants)
    3. Developmental Screening
    4. Measure weight, length and Head Circumference (see precautions above)
    5. Physical exam
    6. Hearing screening (if indicated for high risk infants at 3 months, and repeat again at 9-12 months)
    7. Ophthalmologic screening (6-9 months of age)
    8. Iron Deficiency screening (4 to 6 months of Corrected Age and again at 9-12 months)
    9. Lead level screening at 12-24 months of Corrected Age
      1. Perform as indicated (although AAP still recommends universal screening as of 2014)
    10. Immunizations (see below)

X. Indications: Subspecialty Follow-up

  1. Pulmonology
    1. Oxygen therapy
    2. Cardiorespiratory monitor
    3. Tracheostomy
    4. Bronchopulmonary Dysplasia
  2. Gastroenterology
    1. Enteral Tube Feedings
  3. Neurology
    1. Intraventricular Hemorrhage
    2. Intraventricular shunt
  4. Ophthalmology
    1. Retinopathy of Prematurity
  5. Urology
    1. Cryptorchidism
    2. Inguinal Hernia
  6. References
    1. (2004) Pediatrics 114(Suppl 5): 1377-97 [PubMed]

XI. Evaluation: Outpatient Focus Areas

  1. Assess Nutrition and Growth
    1. See Preterm Infant Growth
    2. See Infant Nutrition
    3. See Preterm Feeding Schedules
    4. See Premature Infant Fluid Requirements
    5. Expect 20-30 grams of weight increase daily for adequate growth
      1. Requires 100 to 120 kcal/kg/day
    6. Use premature growth charts (e.g. Fenton Preterm Growth Chart)
      1. https://ucalgary.ca/resource/preterm-growth-chart/preterm-growth-chart
      2. Infants <1500 grams (consider if <2500 grams) until 50 weeks Gestational Age
        1. After 50 weeks gestation, may return to standard WHO growth charts
    7. Breast Milk is preferred primary source of nutrition for all Gestational Ages
      1. Associated with lower chronic lung disease, NEC, ROP and Sepsis risk
      2. Associated with improved neurocognitive development
      3. Donor Breast Milk may be available in NICU
      4. Fortified Breast Milk with formula may be needed for adequate nutrition
        1. Discontinue fortification after catch-up growth reached (risk of Obesity, hypervitaminosis)
      5. Iron Supplementation 1-2 mg/kg/day
        1. Indicated for Breastfed infants without significant formula supplementation
        2. Formula contains 2 mg/kg/day iron
    8. Formula-fed infants
      1. Use premature formulas (22 kcal/oz)
      2. Avoid soy based formulas (Osteopenia risk)
      3. Provides recommended 2 mg/kg/day iron (no additional Iron Supplementation needed)
    9. Vitamin D Supplementation
      1. Vitamin D 200 to 800 IU/day for first 6 months of life
    10. Iron Supplementation
      1. See Breast Feeding as above
  2. Developmental Examination at each routine Well Child Visit
    1. Evaluation domains in Preterm Infants
      1. Cerebral Palsy (esp. spastic diplegia)
        1. Incidence: 0.3% of Preterm Infants overall (9% very preterm, 2.4% moderate preterm)
        2. Typically diagnosed at 12-24 months (but may be diagnosed accurately at 6 months)
      2. Intellectual Disability
        1. Adjusted Odds Ratio: 14.5 at 24 weeks, 3.6 at at 32 weeks and 1.5 at 37 weeks
        2. Heuvelman (2018) Eur J Epidemiol 33(7):667-78 +PMID: 29214412 [PubMed]
      3. Vision Impairment
        1. Cortical-Visual Impairment
        2. Retinopathy of Prematurity (esp. infants <30 weeks gestation, <1500 g birth weight)
        3. Severe Refractive Error
        4. Strabismus
      4. Hearing Impairment
        1. See Newborn Screening below
    2. Refer if Developmental Delay identified on screening
      1. Programs available to children under age 3 are federally funded
    3. Tools - complete Developmental Screening at 9, 18, and 24-30 months
      1. See Developmental Evaluation
      2. Includes Autism screening at 18 and 24 months
      3. Denver Prescreening Developmental Questionnaire II (R-DPDQ)
      4. Denver Developmental Screening Test II (DDST-2)
  3. Neurologic Examination red flags
    1. Asymmetric motor activity or weakness
    2. Hyperreflexia
    3. Altered Muscle tone (hypertonia or hypotonia)
  4. Vision Evaluation (evaluating Retinopathy of Prematurity)
    1. Initial Retinal Examination: 31 weeks Postmenstrual Age
    2. Subsequent Retinal Examination: Per ophthalmologist based on first exam
  5. Newborn Hearing Screening
    1. Initial examination: Prior to NICU discharge
    2. Subsequent examination
      1. Abnormal NICU Screen OR Hyperbilirubinemia needing Exchange Transfusion (or new concerns)
        1. Repeat outpatient Hearing screening at 3 months
        2. Early intervention by 6 months
      2. Normal NICU Screen and no additional risk factors
        1. Routine repeat testing at 9 months
  6. Immunizations
    1. See below

XII. Labs

  1. Hemoglobin At 6 months and 2 years
  2. Lead level at 9 to 12 months

XIII. Management

  1. See Infant Nutrition
  2. Specific Condition Management
    1. Bronchopulmonary Dysplasia
      1. May require additional Caloric Intake, reactive airway management and home oxygen
    2. Apnea of Prematurity
      1. May require Methylxanthines and apnea monitor
  3. Immunization
    1. Administer via standard Primary Series schedule based on Chronological Age (not adjusted for gestation)
    2. DTaP Vaccine, Hib Vaccine, IPV Vaccine and Prevnar are unaffected by prematurity
    3. Rotavirus Vaccine may be given after age 6 weeks (until 15 weeks) if discharged from NICU and stable
    4. Influenza Vaccine starting at 6 months Chronological Age (2 doses, 4 weeks apart)
    5. Hepatitis B Vaccine
      1. See Hepatitis B Vaccine for schedule and modifications
      2. Modified if known maternal Hepatitis B positive
      3. Birth weight >2000g: Give within 24 hours of birth
      4. Birth weight <2000g: Give when birth weight >2000g OR when age >1 month
    6. Respiratory Syncytial Virus Vaccine (Nirsevimab/Beyfortus or Palivizumab/Synagis)
      1. See RSV Vaccine for indications and dosing schedule
      2. Prenatal RSV Vaccine (Abrysvo) for mothers expected to deliver during RSV season
  4. Pediatric Gastroesophageal Reflux (Pediatric GERD)
    1. See Pediatric GERD
  5. References
    1. Bonhoeffer (2006) Arch Dis Child 91: 929-35 [PubMed]

XIV. Prognosis: Overall Outcome

  1. Formula to estimate survival and morbidity
    1. Percent Survival: (Age in weeks - 20) x 10
    2. Percent Handicap-free: Survival + 10
  2. Example
    1. 23 Weeks: 30% Survival, 40% Handicap-free
    2. 24 Weeks: 40% Survival, 50% Handicap-free
    3. 25 Weeks: 50% Survival, 60% Handicap-free
    4. 26 Weeks: 60% Survival, 70% Handicap-free
    5. 27 Weeks: 70% Survival, 80% Handicap-free
    6. 28 Weeks: 80% Survival, 90% Handicap-free
    7. 29 Weeks: 90% Survival, 95% Handicap-free
    8. 30 Weeks: >95% Survival, >95% Handicap-free

XV. Prognosis: Neurologic Outcome

  1. Extreme prematurity (<25 weeks) is associated with significant risk of cognitive deficits
    1. Cognitive deficit risk: 45-50% (overall)
    2. Age 24 weeks: 74% Cognitive deficit risk
    3. Age 25 weeks: 48% Cognitive deficit risk
    4. Age 26 weeks: 26% Cognitive deficit risk
    5. Kilpatrick (1997) Obstet Gynecol 90:803-8 [PubMed]
  2. Very Premature Infants (27-32 weeks)
    1. Cognitive deficit risk: 28-40%
    2. Stephens (2009) Pediatr Clin North Am 56(3): 631-46 [PubMed]
    3. Vohr (2005) Pediatrics 116(3): 635-43 [PubMed]
  3. Late Preterm Infants (34-37 weeks)
    1. Fourfold increased risk of Cerebral Palsy than term infants
    2. Petrini (2009) J Pediatr 154(2): 169-76 [PubMed]

XVI. Prevention

  1. See Preterm Labor
  2. See Preterm Labor Management

XVII. References

  1. (1998) Pediatrics 102:411-7 [PubMed]
  2. Bybel (2025) Am Fam Physician 112(2): 153-61 [PubMed]
  3. Gauer (2014) Am Fam Physician 90(4): 244-51 [PubMed]
  4. LaHood (2007) Am Fam Physician 76:1159-66 [PubMed]
  5. Verma (2003) Clin Pediatr 42: 299-315 [PubMed]

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