Newborn And Infant Care - USMLE Step 2

1. What is the most likely diagnosis?
   Answer: Cephalohematoma A cephalohematoma is a subperiosteal collection of blood resulting from the rupture of blood vessels between the skull and periosteum. Because it is limited by the periosteum, it does not cross suture lines. It is a common birth injury, especially with instrumental delivery. In contrast, a caput succedaneum is edema of the scalp that is present at birth, poorly demarcated, and crosses suture lines. A subgaleal hemorrhage is a more serious bleed into the potential space between the periosteum and the galea aponeurotica; it is fluctuant, crosses suture lines, and can lead to significant blood loss and shock. A cranial meningocele is a neural tube defect involving protrusion of the meninges through a skull defect.
2. A healthy term newborn fails the initial bedside automated auditory brainstem response (ABR) screening in the right ear but passes in the left ear. There were no risk factors for congenital hearing loss. What is the most appropriate next step?
   Answer: Schedule a repeat ABR of the right ear within 1 month to confirm the result When you encounter newborn hearing screening questions, remember that the goal is to balance early detection with avoiding unnecessary anxiety and overtreatment. Most initial screening failures are due to temporary conditions like fluid or debris in the ear canal. The correct approach for a unilateral screening failure in a low-risk newborn is to schedule repeat testing within 1 month (A). This timeframe allows temporary conditions to resolve while ensuring timely detection of true hearing loss. The repeat test confirms whether the initial failure was a false positive or represents actual hearing impairment. Option B is premature because immediate diagnostic testing is reserved for high-risk infants or those with bilateral failures. Moving straight to diagnostic ABR skips the important confirmation step and may cause unnecessary parental anxiety. Option C puts the cart before the horse. Early intervention is crucial for confirmed hearing loss, but starting speech therapy before confirming the diagnosis wastes resources and creates undue concern when the majority of unilateral failures resolve. Option D represents dangerous false reassurance. While many unilateral failures are indeed false positives, you cannot assume this without proper follow-up testing. Unilateral hearing loss can significantly impact speech and language development if left undetected. Study tip: For USMLE Step 2, remember the "confirm then act" principle for screening tests. Initial screening failures usually warrant repeat testing before jumping to diagnostic procedures or interventions, especially in low-risk populations. The exception is when clinical suspicion is very high or bilateral abnormalities are present.
3. A healthy 39-week neonate is 12 hours old and has normal vital signs and physical examination findings. The nurse asks when the critical congenital heart disease (CCHD) pulse oximetry screen should be performed. What is the most appropriate response?
   Answer: Screen after the infant is 24 hours old or immediately before discharge if discharge occurs first When you encounter questions about newborn screening protocols, focus on the specific timing requirements that balance accuracy with practical implementation. Critical congenital heart disease (CCHD) screening uses pulse oximetry to detect life-threatening heart defects that may not be clinically apparent in the immediate newborn period. The correct timing for CCHD screening is after 24 hours of age OR immediately before discharge if discharge occurs sooner (Answer A). This timing is crucial because it allows sufficient time for normal physiologic changes after birth while ensuring no infant leaves the hospital unscreened. During the first 24 hours, normal transitional circulation changes can cause oxygen saturation fluctuations that would lead to false positive results. Answer B is incorrect because even though major circulatory transition occurs within hours, the screening protocol specifically requires waiting 24 hours to minimize false positives from normal physiologic variations. Answer C is wrong because waiting until the 2-week visit is far too late - many critical heart defects require immediate intervention, and delaying screening until outpatient follow-up could result in life-threatening presentations at home. Answer D is incorrect because CCHD screening is universal, not selective - many critical heart defects present without murmurs in the newborn period, which is precisely why pulse oximetry screening was developed. Remember that newborn screening protocols have specific timing windows based on physiologic principles. For CCHD screening, the key is "24 hours OR before discharge" - this ensures every baby is screened while avoiding the high false positive rate of earlier screening.
4. A 32-week premature infant weighing 1.4 kg is born to a mother who is hepatitis B surface antigen positive. Which of the following hepatitis B immunoprophylaxis regimens is appropriate for this neonate?
   Answer: Administer hepatitis B vaccine and hepatitis B immune globulin within 12 hours of birth When you encounter questions about neonatal hepatitis B immunoprophylaxis, focus on two key principles: timing is critical for preventing perinatal transmission, and premature infants should receive the same protection as term infants. For infants born to hepatitis B surface antigen-positive mothers, the standard of care requires dual immunoprophylaxis within 12 hours of birth, regardless of gestational age or birth weight. This approach provides both immediate passive protection (from hepatitis B immune globulin) and long-term active immunity (from the vaccine). The 12-hour window is crucial because hepatitis B transmission risk is highest immediately after birth through exposure to maternal blood and secretions. Choice A is correct because it follows the established guidelines for high-risk infants, providing optimal protection regardless of the infant's size or gestational age. Choice B is wrong because delaying the vaccine until 2 kg weight gain unnecessarily prolongs the period of vulnerability. Premature infants can mount adequate immune responses to hepatitis B vaccine even at low birth weights. Choice C is incorrect because giving immune globulin at 1 month is far too late—the critical window for preventing perinatal transmission would be missed, and the vaccine alone provides insufficient immediate protection. Choice D fails because delaying both components eliminates any protection during the highest-risk period immediately after birth. Remember this key point: hepatitis B immunoprophylaxis timing never depends on gestational age or weight for infants of positive mothers. The 12-hour rule is absolute, making this a high-yield fact for pediatric infectious disease questions.
5. A term neonate with a family history of cystic fibrosis has not passed meconium at 48 hours. Examination shows abdominal distension but no evidence of Hirschsprung-associated syndromic features. Abdominal radiograph demonstrates dilated small bowel loops with a soap-bubble appearance in the right lower quadrant. Which of the following is the most appropriate next diagnostic step?
   Answer: Perform a water-soluble contrast enema to distinguish meconium ileus from other obstruction When you encounter a neonate with delayed meconium passage, abdominal distension, and a family history of cystic fibrosis, think systematically about neonatal intestinal obstruction. The key clinical clue here is the "soap-bubble appearance" on abdominal radiograph in the right lower quadrant, which is pathognomonic for meconium ileus. Meconium ileus occurs in 10-20% of neonates with cystic fibrosis due to abnormally thick, inspissated meconium that obstructs the terminal ileum. The water-soluble contrast enema (choice A) serves both diagnostic and therapeutic purposes - it can differentiate meconium ileus from other causes of obstruction and may actually relieve the obstruction by drawing fluid into the bowel and softening the impacted meconium. Choice B (rectal biopsy for Hirschsprung disease) is incorrect because the clinical presentation and imaging findings strongly suggest meconium ileus, not aganglionosis. Hirschsprung disease typically doesn't show the characteristic soap-bubble appearance. Choice C (upper GI series for malrotation) is wrong because malrotation usually presents earlier with bilious vomiting and wouldn't produce this specific radiographic pattern in the terminal ileum. Choice D (ultrasound for pyloric stenosis) is incorrect because pyloric stenosis presents with projectile non-bilious vomiting around 2-6 weeks of age, not with failure to pass meconium in a newborn. Study tip: Remember that soap-bubble appearance + family history of CF + delayed meconium passage = meconium ileus. Water-soluble contrast enema is both your diagnostic test and potential first-line treatment.
6. A 4-day-old, exclusively breast-fed girl presents with jaundice. Birth weight was 3.1 kg; she has lost 8% of birth weight, has 4–5 wet diapers and 3 meconium stools daily, and feeds every 4 hours. Total bilirubin is 17 mg/dL; direct fraction is 0.2 mg/dL. Which intervention is most likely to improve her hyperbilirubinemia?
   Answer: Increase the frequency and duration of breastfeeding sessions When you encounter neonatal jaundice in the first week of life, distinguish between breastfeeding failure jaundice (early onset, days 2-4) and breast milk jaundice (later onset, after day 4-7). This case shows classic breastfeeding failure jaundice. The key clues are: 8% weight loss (concerning when >7%), feeding only every 4 hours (inadequate frequency), few wet diapers (4-5 is borderline low), and continued meconium stools at day 4 (should transition to yellow by now). The elevated unconjugated bilirubin (16.8 mg/dL) results from inadequate caloric intake leading to increased enterohepatic circulation and delayed meconium passage. Choice A is correct because increasing breastfeeding frequency and duration addresses the root problem. More frequent feeding (every 2-3 hours) improves caloric intake, promotes weight gain, increases stooling to clear bilirubin, and maintains the breastfeeding relationship. Choice B (expressed breast milk by bottle) doesn't address feeding frequency and unnecessarily disrupts the nursing relationship. Choice C (exclusive formula for 48 hours) is too aggressive and can interfere with breastfeeding establishment, though formula supplementation might be considered if the infant fails to respond to increased nursing. Choice D is incorrect because this isn't benign breast milk jaundice—it's breastfeeding failure requiring intervention. Remember: Early jaundice with poor feeding and weight loss suggests breastfeeding problems, not breast milk itself. Support breastfeeding first before considering alternatives. Watch for the combination of jaundice, weight loss >7%, and feeding issues as your cue to optimize nursing frequency.
7. Parents of a healthy term newborn refuse the intramuscular vitamin K injection because they believe it is unnecessary. Which of the following complications best explains why vitamin K prophylaxis is strongly recommended?
   Answer: Late-onset intracranial hemorrhage from vitamin K deficiency bleeding When you encounter questions about newborn prophylaxis, focus on preventing the most serious complications that healthy newborns are uniquely susceptible to despite appearing normal at birth. Vitamin K prophylaxis prevents vitamin K deficiency bleeding (VKDB), a potentially catastrophic condition in newborns. Babies are born with low vitamin K stores because it poorly crosses the placenta, and breast milk contains minimal amounts. Without adequate vitamin K, newborns cannot properly synthesize clotting factors II, VII, IX, and X, leading to severe bleeding disorders. The most feared complication is late-onset VKDB (occurring 2-12 weeks after birth), which frequently presents as intracranial hemorrhage and can cause permanent neurological damage or death. This makes choice A correct. Choice B incorrectly describes hemolytic anemia from oxidative injury. While vitamin K has some antioxidant properties, its deficiency doesn't cause clinically significant hemolytic anemia in newborns. The primary concern is coagulopathy, not red blood cell destruction. Choice C misrepresents vitamin K's role. Hearing loss and myelination problems aren't associated with vitamin K deficiency. These issues might relate to other nutritional deficiencies or genetic conditions, but not vitamin K. Choice D confuses vitamin K's function. While vitamin K is involved in osteocalcin carboxylation for bone metabolism, tooth enamel hypoplasia isn't a recognized complication of vitamin K deficiency in newborns. The acute bleeding risk far outweighs any theoretical long-term skeletal effects. Remember: Vitamin K prophylaxis prevents bleeding, particularly the devastating intracranial hemorrhages that can occur weeks after an apparently normal birth.
8. What is the most likely cause of this infant's jaundice?
   Answer: ABO incompatibility Jaundice appearing within the first 24 hours of life is always pathologic. In this case, the mother is blood type O and the infant is type A, which sets up the potential for ABO incompatibility. Maternal anti-A antibodies (which are IgG and can cross the placenta) can cause hemolysis in the infant, leading to early-onset and rapidly rising hyperbilirubinemia. Physiologic jaundice typically peaks on days 3-5. Breast milk jaundice occurs later, usually after the first week. Biliary atresia presents with conjugated hyperbilirubinemia, typically at 2-8 weeks of age.
9. At a routine 6-week visit, a male infant still has an attached, moist umbilical stump without signs of infection. He has a history of delayed separation of the cord in an older sibling. Physical examination is otherwise normal. Which of the following diagnostic tests is most appropriate to pursue first?
   Answer: Obtain a complete blood count with differential to evaluate for persistent neutrophilia When you encounter delayed umbilical cord separation (beyond 3 weeks), think systematically about the underlying causes. The most common culprit is leukocyte adhesion deficiency (LAD), particularly when there's a family history of similar delayed separation. The correct approach is A) Complete blood count with differential. In LAD, neutrophils cannot properly migrate to sites of inflammation due to defective adhesion molecules. This leads to persistent, severe neutrophilia (often >20,000/μL) because neutrophils accumulate in circulation rather than migrating to tissues. The CBC is the most straightforward first test and will show this characteristic finding if LAD is present. B) Quantitative immunoglobulin levels assess humoral immunity, but delayed cord separation isn't typically associated with B-cell defects or immunoglobulin abnormalities. C) Sweat chloride testing screens for cystic fibrosis, which doesn't cause delayed cord separation. While CF patients can have increased infection risk, this isn't related to umbilical cord pathophysiology. D) Nitroblue tetrazolium or dihydrorhodamine testing evaluates neutrophil oxidative burst function and would diagnose chronic granulomatous disease (CGD). While CGD causes recurrent infections, it doesn't typically present with delayed cord separation - that's more characteristic of LAD. Study tip: Remember that delayed umbilical cord separation + family history should make you think LAD first. Start with the simple test (CBC) before moving to specialized functional assays. The neutrophilia in LAD is often dramatically elevated and easily spotted on routine labs.
10. Which of the following is the most appropriate initial diagnostic test?
    Answer: Abdominal ultrasound The clinical presentation of projectile, nonbilious vomiting in a 3-6 week old infant, along with a palpable 'olive' in the epigastrium, is classic for hypertrophic pyloric stenosis. Abdominal ultrasound is the diagnostic test of choice, as it is non-invasive, does not involve radiation, and can visualize the thickened, elongated pyloric muscle. An upper GI series would show a 'string sign' but is more invasive and is typically reserved for equivocal cases. An abdominal X-ray is non-specific. Serum electrolytes are important for management (to assess for hypochloremic, hypokalemic metabolic alkalosis) but not for diagnosis.
11. Which of the following is the most appropriate next step?
    Answer: Arrange for an urgent ophthalmology consultation An absent red reflex (leukocoria) is a medical emergency in an infant. It can be a sign of a serious underlying condition such as congenital cataracts, retinoblastoma, glaucoma, or chorioretinitis. Prompt evaluation by an ophthalmologist is crucial to determine the cause and initiate treatment to prevent permanent vision loss or, in the case of retinoblastoma, to save the child's life. Delaying evaluation or relying on parental observation is inappropriate.
12. Which of the following is the most critical initial step in managing this infant?
    Answer: Stop enteral feeds and place a nasogastric tube for decompression Bilious emesis in a neonate is a surgical emergency until proven otherwise, as it may indicate a life-threatening condition such as malrotation with midgut volvulus or intestinal atresia. The most critical initial step is to decompress the stomach by stopping all enteral feeds and placing a nasogastric tube to low intermittent suction. This prevents further abdominal distention and reduces the risk of aspiration. While surgical consultation and diagnostic imaging (like an upper GI series to evaluate for malrotation) are essential next steps, gut decompression is the immediate priority for stabilization.
13. Which of the following is the most appropriate next step in management?
    Answer: Obtain a full sepsis workup and administer empiric antibiotics This infant is presenting with signs and symptoms highly concerning for neonatal sepsis. Neonates with serious infections may present with nonspecific signs like lethargy, poor feeding, and temperature instability (either fever or hypothermia). The presence of mottled skin and delayed capillary refill indicates poor perfusion and possible septic shock. This is a medical emergency. The standard of care is to perform a full sepsis workup (blood culture, urine culture, and lumbar puncture for CSF analysis) and immediately administer broad-spectrum intravenous antibiotics (typically ampicillin and gentamicin or cefotaxime). Delaying treatment can have catastrophic consequences.
14. What is the most likely diagnosis?
    Answer: Congenital adrenal hyperplasia This infant presents with a classic salt-wasting crisis and virilization (ambiguous genitalia). This combination is characteristic of congenital adrenal hyperplasia (CAH), most commonly due to 21-hydroxylase deficiency. The enzyme block prevents the production of cortisol and aldosterone, leading to hypoglycemia, hyponatremia, hyperkalemia, and dehydration (salt-wasting). The precursor hormones are shunted towards androgen production, causing virilization in female infants. Pyloric stenosis causes a hypokalemic, hypochloremic metabolic alkalosis. Androgen insensitivity syndrome results in a phenotypically female infant with a 46,XY karyotype. Turner syndrome (45,X) does not cause salt-wasting or virilization.
15. Which of the following is the most appropriate next step in management?
    Answer: Referral to an orthopedic surgeon This infant has a positive Ortolani test (the 'clunk' felt on abduction and anterior pressure), which indicates a dislocated but reducible hip, diagnostic of developmental dysplasia of the hip (DDH). Breech presentation is a major risk factor. A positive Ortolani or Barlow test at this age requires prompt referral to a pediatric orthopedic surgeon for management, typically with a Pavlik harness. Triple diapering is an outdated and ineffective treatment. Hip X-rays are not reliable in infants younger than 4-6 months because the femoral head is primarily cartilaginous; ultrasound is the preferred imaging modality if needed, but a definitive physical exam finding warrants direct referral.
16. What is the most likely diagnosis?
    Answer: Ventricular septal defect This infant is presenting with signs of heart failure (poor feeding, tachypnea, diaphoresis with feeding). The physical exam finding of a holosystolic murmur at the left lower sternal border is classic for a ventricular septal defect (VSD). Large VSDs cause a significant left-to-right shunt, leading to pulmonary overcirculation and heart failure symptoms around 4-6 weeks of age as pulmonary vascular resistance drops. An ASD typically has a fixed, split S2 and is often asymptomatic in infancy. A PDA has a continuous, machine-like murmur. Tetralogy of Fallot is a cyanotic heart defect with a harsh systolic ejection murmur at the left upper sternal border.
17. What is the most likely diagnosis?
    Answer: Transient tachypnea of the newborn (TTN) Transient tachypnea of the newborn (TTN) is caused by delayed clearance of fetal lung fluid. It is common in infants born via cesarean section without labor, as they miss the 'thoracic squeeze' of vaginal delivery. The clinical picture of mild, early respiratory distress and classic chest X-ray findings of retained fluid (perihilar streaking, fluid in fissures) are characteristic of TTN. RDS is a disease of prematurity caused by surfactant deficiency and shows diffuse reticulogranular 'ground-glass' opacities on X-ray. MAS occurs in the setting of meconium-stained fluid and shows patchy infiltrates. Congenital pneumonia would typically show consolidation.
18. A term boy is 3 days old and exclusively breast-fed. His weight is 8% below birth weight, down from 5% yesterday. He has 5 wet diapers and 4 yellow seedy stools in the past 24 hours. Physical examination is normal. What is the most appropriate management?
    Answer: Provide lactation support and re-weigh the infant in 24 hours When evaluating weight loss in newborns, you need to distinguish normal physiological changes from concerning dehydration. Newborns typically lose 7-10% of birth weight in the first few days due to fluid shifts and initial feeding establishment, with most reaching their nadir by day 3-4. This infant shows reassuring signs despite the 8% weight loss. The key indicators of adequate hydration and nutrition are the wet diapers (5 in 24 hours suggests good urine output) and normal yellow seedy stools (4 indicates successful breastfeeding and proper digestion). The normal physical exam further supports that this is physiological weight loss rather than pathological dehydration. Choice A is correct because lactation support addresses the root issue - optimizing breastfeeding technique - while close monitoring (24-hour recheck) ensures the weight loss curve is plateauing as expected. Choice B (supplemental formula) is premature and can actually undermine breastfeeding success by reducing infant demand and maternal milk production. This intervention should be reserved for clear signs of inadequate intake or continued weight loss beyond 10%. Choice C (IV fluids/admission) is excessive given the normal vital signs, adequate urine output, and absence of dehydration signs like sunken fontanelles or poor skin turgor. Choice D (weekly follow-up) provides insufficient monitoring during this critical period when weight should stabilize and begin recovering. Study tip: For USMLE Step 2, remember that normal newborn weight loss peaks around day 3-4. Focus on functional indicators (wet diapers, stools, exam findings) rather than weight percentage alone when assessing newborn hydration status.
19. Which of the following is the most appropriate initial intervention?
    Answer: Increase breastfeeding frequency and assist with latch This infant has breastfeeding jaundice, also known as lactation failure jaundice. It is caused by suboptimal milk intake, leading to decreased stooling, increased enterohepatic circulation of bilirubin, and dehydration. The infant has signs of dehydration (excessive weight loss, decreased urine output, dry mucous membranes) and is feeding infrequently. The most appropriate initial intervention is to address the underlying cause by increasing the frequency and duration of breastfeeding and ensuring a proper latch. Discontinuing breastfeeding is not recommended. Phototherapy may be needed depending on the bilirubin level, but optimizing feeding is the first step. Exchange transfusion is reserved for severe, life-threatening hyperbilirubinemia.
20. Which of the following is the most appropriate next step in management?
    Answer: Prepare for a double-volume exchange transfusion This infant has severe hyperbilirubinemia due to ABO incompatibility that is not responding to intensive phototherapy and is now showing signs of acute bilirubin encephalopathy (lethargy, high-pitched cry). This is a medical emergency. The definitive treatment to rapidly lower the bilirubin level and remove the antibody-coated red blood cells is a double-volume exchange transfusion. This procedure is indicated for severe hyperbilirubinemia or signs of neurotoxicity. While IVIG can be used as an adjunct to reduce hemolysis, exchange transfusion is the critical intervention at this stage.

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