A premature (preterm) infant is defined as a baby born before 37 completed weeks of gestation . Preterm birth is a major contributor to neonatal morbidity and mortality , especially in low-resource settings .
Classification of Infants by Gestational Age
| Term | Definition |
|---|---|
| Preterm | <37 weeks of gestation |
| Term | 37–41 weeks of gestation |
| Post-term | ≥42 weeks of gestation |
Classification by Birth Weight
| Category | Birth Weight |
|---|---|
| Low Birth Weight (LBW) | <2500 g |
| Very Low Birth Weight (VLBW) | <1500 g |
| Extremely Low Birth Weight (ELBW) | <1000 g |
Etiology and Risk Factors of Preterm Birth
Although many cases occur idiopathically , several maternal, fetal, placental , and social factors contribute.
Maternal Factors
- History of prior preterm birth
- Extremes of maternal age (<17 or >35 years)
- Pre-eclampsia/Eclampsia
- Uterine abnormalities (e.g., bicornuate uterus)
- Cervical insufficiency
- Low pre-pregnancy weight
- Infertility or Assisted Reproductive Technologies (e.g., IVF)
- Recurrent miscarriage or termination
Fetal Factors
- Multiple gestations
- Polyhydramnios
- Fetal anomalies or demise
- First-trimester threatened abortion
Placental and Membrane Factors
- Placenta previa
- Abruptio placentae
- Chorioamnionitis
- Preterm premature rupture of membranes (PPROM)
Social & Environmental Factors
- Low socioeconomic status
- Smoking, alcohol, or illicit drug use
- Psychological stress
- Physically demanding work
Complications of Prematurity
Complications are divided into short-term (neonatal period) and long-term (childhood and beyond).
Short-Term Complications
1. Respiratory System
- Respiratory Distress Syndrome (RDS) : Due to surfactant deficiency.
- Treatment : Antenatal corticosteroids (e.g., dexamethasone), oxygen therapy, NCPAP, surfactant replacement, mechanical ventilation if severe.
- Apnea of Prematurity : Immature brainstem respiratory control.
- Definition : Cessation >20 seconds or <20 seconds with bradycardia/desaturation.
- Treatment : Methylxanthines (e.g., caffeine), NCPAP, mechanical ventilation if severe.
2. Cardiovascular System
- Patent Ductus Arteriosus (PDA)
- Pathophysiology : Left-to-right shunt → pulmonary overcirculation, decreased systemic perfusion.
- Diagnosis : Echocardiography.
- Management : Indomethacin or ibuprofen; surgical ligation if refractory.
3. Central Nervous System
- Intraventricular Hemorrhage (IVH)
- Source : Germinal matrix capillaries.
- Diagnosis : Cranial ultrasound.
- Complications : Grades III/IV associated with hydrocephalus, cerebral palsy.
- Periventricular Leukomalacia (PVL)
- Ischemic injury to periventricular white matter.
- Outcome : Often leads to spastic cerebral palsy.
4. Metabolic and Hepatic
- Hypoglycemia : Due to low glycogen stores and high metabolic demand.
- Hyperglycemia : Due to insulin resistance in VLBW infants.
- Hyperbilirubinemia : From hepatic immaturity and increased RBC turnover.
- Risk : Kernicterus at lower bilirubin levels than term infants.
5. Renal
- Immature kidneys :
- Problems : Electrolyte imbalances (hypernatremia, hyponatremia, hyperkalemia), metabolic acidosis.
- Causes : Poor urine concentrating ability and insensible losses.
6. Gastrointestinal
- Necrotizing Enterocolitis (NEC)
- Presentation : Abdominal distension, bloody stools, apnea, feeding intolerance.
- Diagnosis : Pneumatosis intestinalis on abdominal X-ray.
- Treatment : NPO (nil per os), broad-spectrum antibiotics, surgery if perforation.
- Prevention : Breastfeeding, probiotics.
- Feeding Difficulties
- Due to uncoordinated suck/swallow reflexes and immature GI motility.
- Management : Enteral tube feeding (expressed breast milk preferred), parenteral nutrition initially.
7. Hematologic
- Anemia of Prematurity
- Multifactorial: Reduced erythropoiesis, rapid growth, frequent phlebotomy.
- Management : RBC transfusions, iron supplementation.
8. Immune System
- Infection Risk
- Causes: Underdeveloped immune system, low IgG (from lack of transplacental transfer), frequent invasive procedures.
- Common infections : Sepsis, pneumonia, meningitis.
High-Yield Notes
- Antenatal corticosteroids (betamethasone or dexamethasone) are the standard of care before expected preterm delivery (<34 weeks) to promote lung maturity.
- IVH is most common within the first 48 hours of life in preterms.
- Breast milk is protective against NEC.
- Caffeine citrate is first-line for apnea of prematurity.
- Premature infants often require thermoregulation, infection control, respiratory support , and nutritional supplementation in a NICU setting.
