Neonatology

What are the key clinical signs of respiratory distress in neonates, and what monitoring parameters must be maintained for preterm vs. term infants on oxygen therapy?

Clinical signs of respiratory distress include:
tachypnoea (>60 breaths/min), laboured breathing with chest wall recession, nasal flaring, expiratory grunting, and cyanosis.
Additionally, apnoea must be monitored.
For oxygen therapy: preterm infants must maintain oxygen saturation at 91%–95% (low saturations <91% increase risk of necrotizing enterocolitis and death; high >95% increases risk of retinopathy of prematurity),
while term infants should maintain >95%.
Other monitoring parameters include heart rate, respiratory rate, temperature, blood pressure, blood glucose, blood urea and electrolytes, blood gases, and weight.

What are the indications and uses of different venous/arterial lines in stabilizing a preterm or sick infant?

Peripheral IV line: required for IV fluids, antibiotics, and drugs.
Umbilical venous catheter (UVC): used for IV access during resuscitation, in extremely preterm infants for first few days, or to administer high osmolality fluids (e.g., parenteral nutrition, high-concentration dextrose) or medications needing central delivery (e.g., inotropes).

Arterial line (usually umbilical artery catheter): inserted when frequent blood gas analysis and continuous BP monitoring are required; maintains arterial O2 tension at 8–12 kPa (60–90 mmHg) and CO2 at 4.5–6.5 kPa (35–50 mmHg).
PICC: inserted when infant is stable, used for parenteral nutrition.

What are all the potential medical problems of preterm infants?

Respiratory: RDS, pneumothorax, apnoea and bradycardia. Hypotension. Patent ductus arteriosus. Temperature control issues.

Metabolic: hypoglycaemia, hypocalcaemia, electrolyte imbalance, osteopenia of prematurity.

Nutrition: difficulty establishing feeding, extra-uterine growth impairment. Infection. Jaundice.
Intraventricular haemorrhage/periventricular leukomalacia.
Necrotizing enterocolitis.
Retinopathy of prematurity.
Anaemia of prematurity.
Bronchopulmonary dysplasia (BPD).
Inguinal hernias. Need for resuscitation and stabilization at birth.

What is Respiratory Distress Syndrome (RDS) / Hyaline Membrane Disease? Describe its pathophysiology, incidence by gestational age, clinical signs, CXR appearance, and management.

RDS is caused by deficiency of surfactant — a mixture of phospholipids and proteins secreted by type II pneumocytes — which normally lowers surface tension.
Without surfactant, the lung has poor compliance, leading to atelectasis, decreased gas exchange, and severe hypoxia and acidosis. Histologically, a proteinaceous hyaline membrane lines the airways.

Clinical signs appear within 4 hours of birth: tachypnoea >60 breaths/min, chest wall recession (sternal and subcostal), nasal flaring, expiratory grunting (to maintain FRC), and cyanosis if severe.

CXR:
diffuse granular/ground glass appearance with air bronchogram.

Management: supplemental O2, CPAP or high-flow nasal cannula therapy, surfactant instilled via tracheal tube or fine catheter, mechanical ventilation if no response.
Antenatal glucocorticoids significantly reduce RDS, BPD, IVH, and neonatal mortality.

What are the causes, clinical features, diagnosis, and management of pneumothorax in neonates?

In RDS, overdistended alveoli allow air to track into the interstitium (pulmonary interstitial emphysema), then into the pleural cavity — occurs in up to 10% of ventilated RDS infants. May also occur spontaneously in up to 2% of deliveries.

Clinical features: increased O2 requirement, reduced breath sounds and chest movement on affected side, chest bulge, sudden deterioration.

Diagnosis: transillumination with fibre-optic light in a darkened room (false positives: skin oedema, subcutaneous air, pneumomediastinum; false negatives: thick chest wall, darkly pigmented skin), point-of-care ultrasound, or CXR (definitive).

A tension pneumothorax is treated urgently with needle decompression then chest drain.

Prevention: ventilate with lowest pressures providing adequate chest movement.

What is apnoea of prematurity? Define it, list its causes, and describe its management.

Apnoea of prematurity is cessation of breathing for ≥20 seconds leading to bradycardia and desaturation.

It is a developmental problem with regulation of respiration, generally resolving by 36 weeks CGA.
Incidence is inversely related to gestational age.
Causes: usually immaturity of central respiratory control, but underlying causes to exclude include hypoxia, infection, anaemia, electrolyte disturbance, hypoglycaemia, seizures, heart failure, and aspiration due to gastro-oesophageal reflux.

Management: gentle physical stimulation, caffeine/methylxanthines (demonstrated to improve outcomes), CPAP, or mechanical ventilation if episodes are frequent.

Why are preterm infants particularly vulnerable to hypothermia? List all mechanisms and describe how temperature control is achieved.

Hypothermia causes increased energy consumption, may cause hypoxia, hypoglycaemia, failure to gain weight, and is an independent risk factor for mortality.

Preterm infants are vulnerable because:
(1) large surface area relative to mass → greater heat loss;
(2) thin, heat-permeable skin → significant transepidermal water loss in first week;
(3) little subcutaneous fat;
(4) nursed naked, cannot curl up or shiver.

Prevention addresses four mechanisms —
Convection: raise incubator air temperature, clothe infant including head, avoid draughts;
Radiation: cover baby, use double-walled incubators;
Evaporation: dry and wrap at birth (if extremely preterm, place into plastic bag without drying), humidify incubator;
Conduction: nurse on heated mattress.
Temperature maintained using incubators or overhead radiant heaters.

Describe the pathophysiology, clinical features, diagnosis, and management of Patent Ductus Arteriosus (PDA) in preterm infants.

The DA is a normal fetal connection (PA to aorta, right-to-left shunt in fetus). Postnatally it should close within 12–48 hours via increased O2 (constrictor) and decreased PGE2 (vasodilator).

In preterm infants, sensitivity to O2 as constrictor is lower and sensitivity to PGE2-mediated vasodilation is higher, so DA stays patent.

Causes a left-to-right shunt (steal phenomenon).

Clinical features: systolic murmur (grade ii/vi, ULSB), bounding pulses, widened pulse pressure, increased O2 requirement, worsening respiratory status, metabolic acidosis, signs of heart failure; can be silent.

Diagnosis: clinically + CXR; confirmed by echocardiogram with Doppler. Management: indomethacin (cyclooxygenase inhibitor), ibuprofen, or paracetamol. If medical treatment fails: surgical ligation or catheter-based occlusive device.

Describe the nutritional requirements and feeding strategies for preterm infants, including parenteral nutrition details.

Preterm infants have very high nutritional needs: at 28 weeks, they double birthweight in 6 weeks and treble it in 12 weeks (vs. 5 months/1 year in term infants).

Infants ≥35–36 weeks can suck and swallow; less mature infants need NG/OG tube feeding.

Colostrum should be given within first hours even in very preterm infants. Breast milk may need fortification with protein, phosphate, electrolytes, and calories. Donor breast milk used if maternal milk insufficient.

Very immature/sick infants (<1 kg) usually require parenteral nutrition via PICC or umbilical venous catheter — strict aseptic technique essential due to septicaemia risk. Peripheral PN risks skin damage from extravasation.

Fluid requirements: ~60–90 ml/kg on day 1, increasing by 20–30 ml/kg/day to 150–180 ml/kg/day by day 5.

Explain the nutritional deficiencies of preterm infants — osteopenia, iron deficiency — and why infection risk is high due to immunological immaturity.

Osteopenia of prematurity: prevented by adequate phosphate, calcium, and vitamin D supplementation.

Iron deficiency: most iron is transferred to fetus during last trimester → low stores in preterm infants + blood loss from sampling + inadequate erythropoietin response → iron supplements started at several weeks of age and continued after discharge.

Infection risk: IgG mostly transferred in last trimester (so low IgG in preterm), no IgA or IgM crosses placenta, IgM does not cross placenta at all. All aspects of immune function sub-optimal in vitro. Poor barrier protection. Cervical infection is often a reason for preterm labour itself. High risk of nosocomial infection from indwelling catheters and mechanical ventilation. Infection is a major cause of death, contributing to BPD, brain injury, and later disability.

What is Necrotising Enterocolitis (NEC)? Describe its aetiology, risk factors, clinical features, X-ray findings, and management.

NEC is a serious bowel illness; incidence inversely proportional to gestational age, typically seen in first few weeks of life.

Aetiology: ischaemic injury, bacterial invasion of bowel wall, and altered gut microbiome.

Risk factors: intrauterine growth restriction (especially with antenatal reversed end-diastolic flow on Doppler), perinatal asphyxia, formula feeds, rapid increase in enteral feeds, antibiotics.

Breast milk is protective.

Early signs: feed intolerance, bile-stained vomiting, abdominal distension, bloody stools → shock and respiratory failure.

X-ray: distended bowel loops, intramural gas, gas in portal venous tract, free gas under diaphragm (perforation). Management: stop oral feeds, broad-spectrum antibiotics (aerobic + anaerobic cover), parenteral nutrition, mechanical ventilation, circulatory support. Surgery for perforation, failure of medical management.

Mortality ~20%; long-term: bowel strictures, malabsorption, poor neurodevelopmental outcome.

Describe the types of preterm brain injury — IVH and PVL — including pathophysiology, grading, clinical presentation, and outcomes.

IVH (Intraventricular Haemorrhage): occurs in 25% of very-low-birthweight infants.

Arises from fragile germinal matrix vessels above the caudate nucleus.

Most occur within first 72 hours. More common after perinatal asphyxia, severe RDS, and pneumothorax.

Grading: Grade I — germinal matrix only; Grade II — extends into ventricles; Grade III — large IVH with ventricular dilatation; Grade IV — unilateral haemorrhagic parenchymal infarction (usually causes hemiplegia).

Large IVH → post-haemorrhagic ventricular dilatation → may need VP/subgaleal shunt; ~50% develop cerebral palsy.

PVL (Periventricular Leukomalacia): ischaemic white matter injury; bilateral posterior cysts → 80–90% risk of spastic diplegia with cognitive impairment. More common: non-cystic white matter damage → neurocognitive impairment.

Both IVH and PVL are usually clinically silent. Antenatal glucocorticoids reduce IVH incidence.

What is Retinopathy of Prematurity (ROP)? Describe its pathophysiology, screening criteria, incidence, and treatment.

ROP affects developing blood vessels at the junction of vascularised and non-vascularised retina.
Vascular proliferation may progress to retinal detachment, fibrosis, and blindness.
Risk increased by uncontrolled high oxygen use; even with careful monitoring, ~35% of very-low-birthweight infants develop ROP, with 5% requiring treatment.

Screening: all preterm infants ≤1500 g birthweight or <32 weeks' gestation screened by an ophthalmologist.
Severe bilateral visual impairment in ~1% of very-low-birthweight infants, mostly <28 weeks.
Treatment: laser therapy reduces visual impairment; intravitreal anti-VEGF therapy is under investigation.

What is Bronchopulmonary Dysplasia (BPD) / Chronic Lung Disease (CLD)? Define it, describe its pathophysiology, CXR appearance, management, and long-term risks.

BPD is defined as oxygen requirement at post-menstrual age of 36 weeks. Lung damage is mainly from delay in lung maturation, plus pressure/volume trauma from mechanical ventilation, oxygen toxicity, and infection.

CXR: widespread opacification, cystic changes, fibrosis, and lung collapse.
Management: wean from ventilator to CPAP/high-flow nasal cannula then supplemental O2 over several months. Short, low-dose corticosteroid courses may facilitate earlier weaning in highest-risk infants (limited use due to neurodevelopmental concerns). Some infants go home on oxygen with RSV prophylaxis needed.
Long-term risks: respiratory failure from pertussis and respiratory viral infection (RSV, rhinovirus); increased risk of wheezing/bronchiolitis in infancy.

Describe the long-term neurodevelopmental outcomes of preterm infants after discharge.

About 5–10% of very-low-birthweight infants develop cerebral palsy, but the most common impairment is learning difficulties.
Prevalence of cognitive impairment increases with decreasing gestational age (greatest if <26 weeks).

Specific difficulties: fine motor skills, concentration and short attention span, behaviour (attention deficit disorders), abstract reasoning (mathematics), processing multiple tasks simultaneously.

Hearing impairment: 1–2% require amplification.
Visual impairment: 1% blind in both eyes; more have refractive errors/squints.
As adults: less socially engaged, poorer communication, more easily anxious — negatively impacting relationships and careers.
Growth and neurodevelopment monitored using corrected age until 2 years old.

Why does neonatal jaundice occur physiologically, and why is it clinically important?

Over 50% of newborns become visibly jaundiced.
Physiological reasons:
(1) marked haemoglobin release from red cell breakdown due to high haemoglobin concentration at birth;
(2) red cell lifespan in neonates is only 70 days (vs. 120 days in adults);
(3) hepatic bilirubin metabolism is less efficient in first few days. Also: low UDPGT activity, absence of intestinal flora, slow intestinal motility, and increased enterohepatic circulation.

Clinical importance:
(1) jaundice may signal another disorder (haemolytic anaemia, infection, inborn error of metabolism, liver disease);
(2) unconjugated bilirubin can deposit in the brain — particularly the basal ganglia — causing kernicterus.

Describe bilirubin metabolism from production to excretion, including the enterohepatic circulation in neonates.

Bilirubin is produced from breakdown of haem (iron protoporphyrin) in the reticuloendothelial system and bone marrow. Haem oxygenase cleaves haem into: iron (conserved), carbon monoxide (exhaled), and biliverdin → converted to unconjugated bilirubin (indirect, lipid-soluble, water-insoluble) by bilirubin reductase.
Unconjugated bilirubin binds albumin → carried to liver → hepatocytes conjugate it with glucuronide molecules via UDPGT (glucuronyltransferase) → conjugated bilirubin (direct, water-soluble) → excreted in bile into intestine → metabolised by gut flora → excreted in stool as stercobilinogen and urobilinogen.
In neonates, absence of gut flora and slow GI motility causes intestinal stasis of conjugated bilirubin; mucosal β-glucuronidase deconjugates it → unconjugated bilirubin reabsorbed (enterohepatic circulation), increasing bilirubin load.

What is kernicterus? Describe its pathophysiology, acute and chronic manifestations, and which populations are at highest risk.

Kernicterus is encephalopathy resulting from deposition of unconjugated bilirubin in the basal ganglia and brainstem nuclei.

Occurs when unconjugated bilirubin exceeds albumin-binding capacity → free unconjugated bilirubin (fat-soluble) crosses blood–brain barrier.

Acute manifestations: lethargy and poor feeding;
severe: irritability, increased muscle tone, opisthotonos (arched back), seizures, and coma.
Chronic manifestations: choreoathetoid cerebral palsy (basal ganglia damage), learning difficulties, and sensorineural deafness. Historically important in severe Rh haemolytic disease; rare now due to anti-D prophylaxis.
Still occurs in slightly preterm (35–37 weeks) and dark-skin-toned infants (harder to detect clinically).
Drugs displacing bilirubin from albumin (e.g., sulphonamides, diazepam) must be avoided in neonates.

What are the causes of neonatal jaundice by age of onset? List all causes systematically.

Jaundice at <24 hours (urgent — haemolytic until proven otherwise):
Rh incompatibility, ABO incompatibility, G6PD deficiency, Spherocytosis/pyruvate kinase deficiency,
Congenital infection (conjugated bilirubin, with growth restriction, hepatosplenomegaly, thrombocytopenic purpura).

Jaundice at 24 hours to 2 weeks:
Physiological jaundice, Breast milk jaundice, Infection (e.g., UTI), Haemolysis (G6PD, ABO), Bruising, Polycythaemia (venous haematocrit >0.65), Crigler–Najjar syndrome.

Jaundice at >2 weeks (Unconjugated):
Physiological or breast milk jaundice, Infection (especially UTI), Hypothyroidism, Haemolytic anaemia (G6PD), High GI obstruction (e.g., pyloric stenosis).

Jaundice at >2 weeks (Conjugated >25 µmol/l):
Bile duct obstruction (biliary atresia — must not delay surgical treatment), Neonatal hepatitis.

Describe phototherapy and exchange transfusion for neonatal jaundice — mechanisms, indications, complications, and key considerations.

Phototherapy: Light at ~450 nm (blue-green spectrum) converts unconjugated bilirubin into a harmless water-soluble pigment excreted mainly in urine. Delivered by overhead light at optimal distance for high irradiance. Eyes must be covered.

Complications: temperature instability, macular rash, and bronze skin discolouration if jaundice is conjugated.

Intensive phototherapy is used if bilirubin is rising rapidly or at high levels. Has greatly reduced need for exchange transfusion. IVIG reduces need for exchange transfusion in Rh/ABO incompatibility unresponsive to phototherapy.

Exchange transfusion: blood removed in small aliquots (from arterial line or umbilical vein) and replaced with donor blood. Volume: 2 × 90 ml/kg (twice infant's blood volume).
Donor blood screened for CMV, hepatitis B/C, HIV — as fresh as possible.
In Rh disease, kernicterus prevented by keeping bilirubin below (20 mg/dl). NICE guidelines ensure uniform UK practice.

Explain ABO incompatibility and Rh haemolytic disease — pathophysiology, clinical presentation, Coombs test, and management differences.

ABO incompatibility: Some group O women have IgG anti-A-haemolysin that crosses the placenta and haemolyses group A (or B) infant red cells.
15% of pregnancies are "setups" but only 1/3 have positive Coombs test and <10% develop significant jaundice.
Haemoglobin usually normal/mildly reduced; hepatosplenomegaly absent. Jaundice peaks at 12–72 hours. Now more common than Rh disease.

Rh isoimmunisation: More severe and more predictable than ABO; severity increases with each immunised pregnancy. Prevented by giving high-titer anti-D (Rho-D) immunoglobulin to Rh-negative women after invasive procedures, miscarriage, abortion, or delivery.

Affected neonates: anaemic at birth, continued haemolysis.

Most severe form: erythroblastosis fetalis — life-threatening anaemia, generalised oedema, fetal/neonatal heart failure → intrauterine transfusion of Rh-negative cells into umbilical vein or fetal abdominal cavity.
Postnatal: phototherapy at delivery, exchange transfusion often needed, IVIG to reduce exchange transfusion; monitor for 2–3 months for recurrent anaemia. Direct antibody test (Coombs) is positive in both conditions.

Describe G6PD deficiency as a cause of neonatal jaundice — epidemiology, mechanism, genetics, and diagnostic pitfall.

G6PD deficiency is the most common red cell enzyme defect causing haemolysis.
Mainly affects infants of African, Mediterranean, or Asian descent. X-linked, but female heterozygotes are also at increased risk due to X-chromosome inactivation.
Mechanism: both increased bilirubin production (haemolysis) and decreased rate of bilirubin conjugation contribute.
Diagnostic pitfall: G6PD enzyme activity is high in reticulocytes, so neonates with many reticulocytes may have falsely normal enzyme tests — repeat testing at 3 months of age is indicated in suspected cases with initially normal results.
A low G6PD level should always raise suspicion.
Parents must be given a list of drugs to avoid (which may precipitate haemolysis).

Distinguish between physiological jaundice, breast-feeding–associated jaundice, and breast milk jaundice — key differences in mechanism, timing, and management.

Physiological jaundice:
Appears after 24 hours of age; total bilirubin rises <5 mg/dL per day; peaks at 3–5 days at ≤15 mg/dL; resolves by 1 week (term) or 2 weeks (preterm). Due to low UDPGT activity, high red cell mass, absent intestinal flora, slow intestinal motility, and increased enterohepatic circulation. Diagnosis of exclusion.

Breast-feeding–associated jaundice ("lack of breast milk" jaundice):
Poor enteral intake → exaggerated enterohepatic circulation. Breastfed infants have 9% incidence vs. 2% in formula-fed.
May signal failure to establish milk supply.
Management: supplement formula if needed, nurse more frequently, use electric breast pump every 2 hours, lactation specialist consultation. Follow-up 2 days after discharge (AAP recommendation).

Breast milk jaundice:
Unconjugated hyperbilirubinaemia lasting 2–3 months in a thriving breastfed infant without haemolysis, hypothyroidism, or other disease.
Benign; affects up to 15% of healthy breastfed infants; resolves by 12 weeks. Cause multifactorial — may involve increased enterohepatic circulation.

What is Crigler–Najjar syndrome and Gilbert syndrome? Describe genetics, mechanism, severity, and treatment.

Crigler–Najjar syndrome: mutations in UDPGT gene.
Type I: complete (or near-complete) absence of glucuronyltransferase — autosomal recessive; severe — causes severe unconjugated hyperbilirubinaemia, bilirubin encephalopathy, and death if untreated; liver transplantation is curative.

Type II: partial UDPGT deficiency — autosomal dominant; phenobarbital can induce the enzyme, lowering bilirubin by 30–80%. Both cause significantly elevated unconjugated bilirubin and risk of kernicterus.

Gilbert syndrome: Common, mild autosomal dominant disorder caused by genetic polymorphism at the UDPGT gene promoter region → decreased hepatic UDPGT activity. ~9% of population homozygous, ~42% heterozygous.
Affected individuals develop hyperbilirubinaemia under increased bilirubin load and are more likely to have prolonged neonatal jaundice and breast milk jaundice.

Describe the clinical features of neonatal sepsis and differentiate early-onset from late-onset neonatal sepsis — organisms, risk factors, and treatment.

Clinical features of neonatal sepsis:
Respiratory distress, fever/temperature instability/hypothermia, poor feeding, vomiting, apnoea and bradycardia, abdominal distension, jaundice, neutropenia, hypoglycaemia/hyperglycaemia, shock, irritability, seizures, lethargy/drowsiness.

In meningitis additionally:
tense or bulging fontanelle and opisthotonos (late signs).
Early-onset (<72 hours): Vertical exposure (ascending or intrapartum). Organisms: GBS, E. coli, Klebsiella, Pseudomonas, rarely Listeria.

Treatment: benzylpenicillin/ampicillin + gentamicin. Stop after 36–48 hours if cultures and CRP negative and no clinical indicators.
Late-onset (>72 hours): Source: hospital (nosocomial) or community. Most common: coagulase-negative staphylococcus (CONS).

Others: S. aureus, E. faecalis, E. coli, Pseudomonas, Klebsiella, Serratia. Initial therapy: flucloxacillin + gentamicin. Use vancomycin if CONS/enterococci resistant; meropenem for broad-spectrum. Prolonged/broad-spectrum antibiotics → risk of invasive Candida albicans infection.
CRP: helpful but takes 12–24 hours to rise; two consecutive normal values strongly exclude infection.

Describe Group B Streptococcal (GBS) infection — epidemiology, risk factors, prevention strategies, and clinical presentations (early and late onset).

Colonisation: 15–40% of pregnant women have rectal/vaginal GBS; ~50% of their infants become colonised; 1–2% of colonised infants develop early-onset infection.

Risk factors: preterm (especially with preterm prolonged rupture of membranes), prolonged (>18 hours) or prelabour rupture of membranes, intrapartum fever >38°C or chorioamnionitis, previous child with GBS infection, GBS bacteriuria during pregnancy.

Early-onset: presents within 24 hours with respiratory distress; most have sepsis without focus; pneumonia/meningitis in 5–10%; mortality 2–4% (higher in preterm).
Late-onset: presents up to 3 months; usually sepsis without focus; may cause pneumonia, meningitis, osteomyelitis, or septic arthritis.

Prevention — UK/Netherlands risk-based approach: prophylactic intrapartum antibiotics if GBS detected or risk factors present. USA/Australia: routine screening at 35–37 weeks; prophylaxis offered to GBS-positive or high-risk women.

Describe the causes of respiratory distress in term infants and describe Transient Tachypnoea of the Newborn (TTN) in detail.

Pulmonary causes — Common: TTN.

Less common: Meconium aspiration, Pneumonia, RDS, Pneumothorax, PPHN. Rare: Diaphragmatic hernia, Tracheo-oesophageal fistula, Pulmonary hypoplasia, Milk aspiration, Choanal atresia, Pulmonary haemorrhage.

Non-pulmonary: Congenital heart disease, Hypoxic-ischaemic/neonatal encephalopathy, Severe anaemia, Metabolic acidosis, Sepsis.

TTN (also known as RDS type 2 or Wet Lung): most common cause of neonatal RD (>40% of cases).

Caused by delayed resorption of fetal lung liquid by lymphatics. Normally, rising adrenaline during labour halts liquid secretion and begins resorption — without labour (elective CS), this adrenaline switch is delayed. Typically affects term and late preterm neonates; more common post-elective CS or in male gender.

CXR: perihilar streaking, fluid to in horizontal fissure.

Mild-to-moderate distress within 2 hours of delivery, resolves within 3 days. Management: supplemental oxygen, NG feeds or IV fluids if unable to feed. Diagnosis of exclusion.

Describe Meconium Aspiration Syndrome (MAS) — epidemiology, pathophysiology, clinical features, CXR, and management.

Meconium is passed before birth by 8–20% of babies; increases with gestational age (20–25% by 42 weeks); only 4–5% of infants with meconium-stained fluid develop MAS.

Pathophysiology: Hypoxia stimulates fetal peristalsis, relaxes anal sphincter, and stimulates gasping → aspiration of viscid meconium.

Consequences —
Chemical: pneumonitis and attenuated immune response.
Mechanical: Complete obstruction → atelectasis;
Partial ball-valve obstruction → over-inflation, emphysema, barrel-shaped chest, air leaks.

Risk populations:
term/post-term (not pre-term) infants with intrauterine hypoxia, maternal hypertension/pre-eclampsia/eclampsia, oligohydramnios, maternal diabetes/heavy smoking.

Clinical features:
barrel-shaped chest (over-inflation),
meconium staining of skin/cord/amniotic fluid;
some asymptomatic at birth then worsen.

CXR:
bilateral scattered atelectasis,
obstructive emphysema, pneumonitis; air leak possible.

Management (delivery room):
oral/pharyngeal suction, oxygen, prophylactic antibiotics, IV fluids.

NICU: oxygen and mechanical ventilation; treat PPHN and pneumothorax. No evidence that tracheal suctioning of vigorous infants reduces MAS.

Describe Persistent Pulmonary Hypertension of the Newborn (PPHN) — pathophysiology, clinical features, diagnosis, and management.

PPHN is a life-threatening condition associated with hypoxic-ischaemic encephalopathy, meconium aspiration, septicaemia, or RDS; sometimes primary.

High pulmonary vascular resistance → right-to-left shunting within the lungs and at atrial and ductal levels.

Clinical features: Cyanosis soon after birth; heart murmurs and heart failure signs often absent.

CXR: heart of normal size; possible pulmonary oligaemia.

Urgent echocardiogram: exclude congenital heart disease; identify raised pulmonary pressures and tricuspid regurgitation.

Management: most require mechanical ventilation and circulatory support.

Inhaled nitric oxide (potent vasodilator) — often beneficial. Sildenafil (Viagra) — occasionally used. High-frequency or oscillatory ventilation — sometimes helpful. ECMO (heart-lung bypass for several days) — for severe but reversible cases, performed in few specialist centres only.

Describe congenital diaphragmatic hernia (CDH) — epidemiology, antenatal detection, clinical features, pathophysiology, and management.

Many diagnosed on antenatal ultrasound at 18–20 weeks.
Neonatal presentation: failure to respond to resuscitation, or severe respiratory distress with scaphoid (sunken) abdomen and heart sounds/apex beat shifted to the right (usually left-sided herniation of abdominal contents through posterolateral foramen of Bochdalek).

CXR/AXR: loops of bowel in left chest, mediastinal displacement. Vigorous resuscitation may cause pneumothorax in the normal lung.

Management: once suspected, pass large NG tube and apply suction (prevents intrathoracic bowel distension). Stabilise ventilation first.

Main problems: pulmonary hypoplasia (compression by herniated viscera throughout pregnancy prevents fetal lung development) and pulmonary hypertension.

Subsequently: surgical repair. Mortality is high if lungs are hypoplastic.

Describe neonatal meningitis — clinical features, organisms, diagnostic workup, management, and complications.

Neonatal meningitis is uncommon but has high mortality and serious sequelae.

Presentation is non-specific (same as sepsis): respiratory distress, temperature instability, poor feeding, apnoea, lethargy, seizures.

Importantly, bulging fontanelle and opisthotonos are late signs, rarely seen in neonates.

Lumbar puncture essential for CSF culture if meningitis suspected.

Treatment: ampicillin or penicillin PLUS third-generation cephalosporin (e.g., cefotaxime, with CSF penetration).

Complications: cerebral abscess, ventriculitis, hydrocephalus, hearing loss, and neurodevelopmental impairment.

Organisms: early-onset — GBS, E. coli, Listeria; late-onset — CONS, S. aureus, Gram-negatives.

CRP: helpful but takes 12–24 hours to rise; two consecutive normal values strongly exclude infection; one normal does NOT exclude. Antibiotics stopped after 36–48 hours if cultures and CRP negative with no clinical indicators.

What is Listeria monocytogenes infection in neonates? How is it transmitted, what are its characteristic features, and how does it differ from GBS infection?

Listeria infection is uncommon but serious.

Transmission: organism ingested by mother in contaminated food (unpasteurised milk, soft cheeses, undercooked poultry) → maternal bacteraemia (often mild influenza-like illness) → transplacental passage to fetus.

Maternal effects: spontaneous abortion, preterm delivery, or fetal/neonatal sepsis.

Characteristic neonatal features: meconium staining of amniotic liquor in preterm infants (unusual and characteristic), widespread rash, septicaemia, pneumonia, and meningitis.High mortality.

Key differences from GBS: Listeria is transmitted via maternal food intake (not genital tract colonisation); produces meconium staining in preterm infants (GBS does not); treatment is ampicillin/penicillin (same as GBS empirical therapy). A third-generation cephalosporin alone is not adequate for Listeria — ampicillin must be included.