USMLE Step 2 Quiz
Practice Newborn And Infant Care in USMLE Step 2 with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.
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A term male infant is born via spontaneous vaginal delivery. At 1 minute of life, his heart rate is 90/min, he has a weak cry, some flexion of his extremities, grimaces in response to suctioning, and his body is pink with blue extremities. At 5 minutes of life, his heart rate is 120/min, he has a strong cry, is actively moving, cries and pulls away from suctioning, and his entire body is pink. The pregnancy was uncomplicated.
What is the 5-minute Apgar score for this infant?
This quiz focuses on Newborn And Infant Care, giving you a quick way to practice the rules, question types, and explanations that matter most for USMLE Step 2.
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A term male infant is born via spontaneous vaginal delivery. At 1 minute of life, his heart rate is 90/min, he has a weak cry, some flexion of his extremities, grimaces in response to suctioning, and his body is pink with blue extremities. At 5 minutes of life, his heart rate is 120/min, he has a strong cry, is actively moving, cries and pulls away from suctioning, and his entire body is pink. The pregnancy was uncomplicated.
What is the 5-minute Apgar score for this infant?
Explanation: The Apgar score is assessed at 1 and 5 minutes of life and consists of 5 components, each scored 0, 1, or 2. At 5 minutes: Appearance (all pink) = 2 points. Pulse (>100/min) = 2 points. Grimace (cries and pulls away) = 2 points. Activity (actively moving) = 2 points. Respiration (strong cry) = 2 points. The total 5-minute Apgar score is 2+2+2+2+2 = 10. The 1-minute Apgar score was 6 (Appearance=1, Pulse=1, Grimace=1, Activity=1, Respiration=2).
A 7-day-old asymptomatic male infant is brought for his first well-child visit. He was born at term and is exclusively breastfed. The state's newborn screening report from a blood spot collected at 48 hours of life returns today and shows a low thyroxine (T4) level and an elevated thyroid-stimulating hormone (TSH) level.
Which of the following is the most appropriate next step in management?
Explanation: An abnormal newborn screen for congenital hypothyroidism (low T4, high TSH) is a medical urgency. The next step is to confirm the diagnosis with a confirmatory serum T4 and TSH test. If confirmed, treatment with levothyroxine should be started immediately to prevent irreversible intellectual disability. Repeating the screen or delaying confirmation is inappropriate. Starting empiric therapy before confirmation is generally not done, as the screening test has false positives.
A 1-day-old term male infant develops jaundice. He was born via uncomplicated vaginal delivery to a 28-year-old G1P1 mother with blood type O-positive. The infant's blood type is A-positive. The infant is otherwise vigorous and feeding well. Total bilirubin is 8.5 mg/dL.
What is the most likely cause of this infant's jaundice?
Explanation: 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.
During a 2-week well-child visit, a physical examination of a female infant reveals a palpable 'clunk' when the left hip is abducted with anterior pressure. The right hip examination is normal. The infant was born in a breech presentation.
Which of the following is the most appropriate next step in management?
Explanation: 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.
A 5-day-old exclusively breastfed male infant is brought to the clinic for jaundice. He was born at term. The mother reports that her milk 'came in' yesterday. The infant feeds every 4-5 hours for about 10 minutes. He has had 2 wet diapers in the past 24 hours. On examination, the infant is jaundiced to the chest and has dry mucous membranes. His weight is down 12% from his birth weight.
Which of the following is the most appropriate initial intervention?
Explanation: 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.
A 4-week-old male infant is brought to the emergency department with a 1-week history of progressively worsening vomiting. The mother describes the vomiting as forceful and projectile, occurring shortly after feeding. The vomitus does not contain bile. The infant seems hungry immediately after vomiting. On examination, a small, olive-shaped mass is palpated in the right upper quadrant.
Which of the following is the most appropriate initial diagnostic test?
Explanation: 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.
During the routine newborn examination of a term male infant, the pediatrician notes an absent red reflex in the left eye. The examination of the right eye reveals a normal, bright red reflex.
Which of the following is the most appropriate next step?
Explanation: 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.
A 2-day-old male infant develops bilious vomiting. He was born at term via uncomplicated delivery. His abdomen is soft but appears distended. He has not yet passed meconium. An abdominal X-ray shows dilated loops of small bowel with a lack of air in the rectum.
Which of the following is the most critical initial step in managing this infant?
Explanation: 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.
A 4-day-old, term infant who is B-positive and born to an O-negative mother develops significant jaundice. The total serum bilirubin is 22 mg/dL, and it is rising despite intensive phototherapy. The infant is becoming increasingly lethargic and developing a high-pitched cry.
Which of the following is the most appropriate next step in management?
Explanation: 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.
A 4-month-old infant, who is exclusively breastfed, is brought in for a well-child check. The mother is concerned about his weight. His birth weight was 3.4 kg. He now weighs 5.0 kg, which is at the 3rd percentile. He was previously tracking along the 25th percentile. The mother reports that he seems fussy at the breast and often feeds for only 5 minutes at a time before crying. The number of wet and dirty diapers has decreased recently.
Which of the following is the most appropriate initial recommendation?
Explanation: The infant is showing signs of poor weight gain ('falling off the curve'), suggesting inadequate caloric intake. Before recommending major changes like supplementation or extensive lab workup, the most important first step is to assess the feeding process directly. Observing a feeding session allows the physician to evaluate the mother's technique, the infant's latch, milk transfer, and the overall mother-infant interaction. This can often identify simple, correctable issues (e.g., poor latch, positioning problems). Starting solids is not recommended before 4-6 months. Switching to formula or ordering labs would be subsequent steps if an observed feed does not reveal the problem.
A 6-week-old infant presents with a 2-week history of poor feeding, sweating during feeds, and rapid breathing. On examination, the infant is tachypneic and has a grade 3/6 holosystolic murmur best heard at the left lower sternal border. There is a palpable thrill and a prominent apical impulse.
What is the most likely diagnosis?
Explanation: 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.
An infant is born at 30 weeks gestation. Within minutes of birth, he develops severe respiratory distress with marked tachypnea, grunting, and cyanosis. A chest X-ray shows diffuse, fine reticulogranular opacities ('ground-glass' appearance) and air bronchograms.
The condition affecting this infant is primarily caused by a deficiency of which of the following?
Explanation: The clinical presentation and radiographic findings in this preterm infant are classic for neonatal respiratory distress syndrome (RDS). RDS is caused by a deficiency of pulmonary surfactant, which is produced by type II pneumocytes. Surfactant reduces alveolar surface tension, preventing atelectasis at the end of expiration. Without adequate surfactant, the alveoli collapse, leading to poor gas exchange, hypoxia, and respiratory failure. Fetal lung fluid retention causes TTN. Alpha-1 antitrypsin deficiency causes emphysema later in life. Vascular endothelial growth factor is involved in angiogenesis.
A 2-day-old jaundiced infant has a total serum bilirubin of 15 mg/dL. The mother's blood type is O-positive, and the infant's is B-positive. A direct antiglobulin (Coombs) test performed on the infant's blood is positive.
This result indicates which of the following processes is occurring in the infant?
Explanation: A positive direct antiglobulin test (DAT or Coombs test) detects antibodies attached to the surface of the infant's red blood cells. In this case of ABO incompatibility (mother O, infant B), the mother has anti-B antibodies (IgG) that have crossed the placenta and are coating the infant's RBCs. This leads to their destruction by the infant's reticuloendothelial system, causing antibody-mediated hemolysis, which results in anemia and hyperbilirubinemia. Increased enterohepatic circulation is a mechanism in breastfeeding jaundice. Decreased conjugation is seen in Gilbert or Crigler-Najjar syndromes. Impaired biliary excretion causes cholestasis.
A 4-day-old, term, exclusively breastfed infant is seen for a well-child check. The birth weight was 3.5 kg. Today's weight is 3.2 kg. The infant has had 6 wet diapers and 4 yellow, seedy stools in the past 24 hours. The mother reports the infant latches well and feeds every 2-3 hours. Physical examination is unremarkable.
Which of the following is the most appropriate recommendation?
Explanation: Newborns can lose up to 10% of their birth weight in the first week of life due to excretion of excess fluid acquired in utero. This infant has lost (3.5 - 3.2) / 3.5 = 8.6% of birth weight, which is within the normal physiologic range. The infant has adequate urine and stool output, indicating sufficient milk intake. Therefore, the most appropriate management is reassurance and continuation of exclusive breastfeeding. Supplementation is not indicated, as there are no signs of dehydration or excessive weight loss.
A 12-hour-old infant is noted to have a firm, well-demarcated swelling over the right parietal bone. The swelling does not cross the suture line. There is no discoloration of the overlying scalp. The infant was born via a vacuum-assisted vaginal delivery.
What is the most likely diagnosis?
Explanation: 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.
A 2-month-old infant is brought to the clinic for frequent spitting up. The mother reports the infant spits up a small amount of milk after most feedings but does not seem to be in pain. The infant is gaining weight appropriately along the 50th percentile and is otherwise healthy and happy. Physical examination is normal.
Which of the following is the most appropriate initial management?
Explanation: This infant has uncomplicated gastroesophageal reflux (GER), often called 'physiologic reflux' or being a 'happy spitter'. This is a common and benign condition in infants due to an immature lower esophageal sphincter. Since the infant is thriving, gaining weight well, and not showing signs of distress (e.g., pain, arching, feeding refusal), this is not gastroesophageal reflux disease (GERD). The most appropriate management is reassurance and conservative measures, such as holding the infant upright after feeds and burping frequently. Medical or diagnostic interventions are not indicated for uncomplicated GER.
A female infant is born at 41 weeks' gestation. The amniotic fluid was thick with meconium. At delivery, the infant is limp and has a heart rate of 80/min. She is intubated and suctioned, but develops grunting, tachypnea, and cyanosis within the first hour of life. A chest x-ray shows coarse, patchy infiltrates and hyperinflation.
What is the most likely diagnosis?
Explanation: The combination of a post-term infant, meconium-stained amniotic fluid, and respiratory distress shortly after birth is highly suggestive of meconium aspiration syndrome (MAS). The meconium in the lungs causes airway obstruction, chemical pneumonitis, and surfactant inactivation. The chest X-ray findings of patchy infiltrates and hyperinflation are classic for MAS. While persistent pulmonary hypertension of the newborn (PPHN) can be a complication of MAS, MAS is the primary diagnosis. Sepsis is in the differential, but the specific history points strongly to MAS. TTN is less likely in a post-term infant and has different X-ray findings.
A 10-day-old female newborn is brought to the emergency department for evaluation of poor feeding and vomiting. Physical examination reveals clitoromegaly and partial fusion of the labial folds. The infant appears dehydrated with sunken fontanelles and tachycardia. Laboratory studies show: Sodium 125 mEq/L, Potassium 6.8 mEq/L, Glucose 55 mg/dL.
What is the most likely diagnosis?
Explanation: 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.
A 10-day-old infant is brought to the emergency department with a 1-day history of poor feeding, lethargy, and a temperature of 36.1°C (97.0°F). The mother reports the infant has been less active than usual and has had fewer wet diapers. On examination, the infant appears listless, has mottled skin, and a capillary refill time of 4 seconds.
Which of the following is the most appropriate next step in management?
Explanation: 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.
A term infant is delivered via elective cesarean section due to breech presentation. Shortly after birth, the infant develops tachypnea, nasal flaring, and mild intercostal retractions. Oxygen saturation is 94% on room air. A chest X-ray reveals prominent perihilar streaking, fluid in the interlobar fissures, and a lack of consolidation.
What is the most likely diagnosis?
Explanation: 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.