A 12-month-old girl is brought to her pediatrician for a checkup and vaccines. The patient’s mother wants to send her to daycare but is worried about exposure to unvaccinated children and other potential sources of infection. The toddler was born at 39 weeks gestation via spontaneous vaginal delivery. She is up to date on all vaccines. She does not walk yet but stands in place and can say a few words. The toddler drinks formula and eats a mixture of soft vegetables and pureed meals. She has no current medications. On physical exam, the vital signs include: temperature 37.0°C (98.6°F), blood pressure 95/50 mm Hg, pulse 130/min, and respiratory rate 28/min. The patient is alert and responsive. The remainder of the exam is unremarkable. Which of the following is most appropriate for this patient at this visit?

Gross motor workup and evaluation

A 12-month-old boy presents for a routine checkup. The patient immigrated from the Philippines with his parents a few months ago. No prior immunization records are available. The patient’s mother claims that he had a series of shots at 6 months of age which gave him a severe allergic reaction with swelling of the tongue and the face. She also remembers that he had the same reaction when she introduced solid foods to his diet, including carrots, eggs, and bananas. Which of the following vaccinations are not recommended for this patient?

Intramuscular influenza vaccine

Measles, mumps, and rubella (MMR) vaccine

An 11-month-old boy is brought to a pediatrician by his parents for evaluation of vomiting and watery diarrhea over the last day. The mother informs the pediatrician that the boy had consumed an apple bought from a fruit vendor on the previous day, but that otherwise there has been no recent change in his diet. There is no history of blood in the stool, flatulence, irritability, or poor appetite. There is no history of recurrent or chronic diarrhea or any other gastrointestinal symptoms. On physical examination, his temperature is 37.6°C (99.6°F), pulse is 120/min, respirations are 24/min, and blood pressure is 92/60 mm Hg. General examination reveals a playful infant with normal skin turgor and no sunken eyes. The pediatrician explains to the parents that he most likely has acute gastroenteritis and that no specific medication is indicated at present. He also instructs the parents about his diet during the illness and reviews the danger signs of dehydration. He suggests a follow-up evaluation after 48 hours or earlier if any complications arise. Which of the following dietary recommendations did the pediatrician make?

Plenty of juices and carbonated sodas

A 3-year-old boy is brought to your pediatrics office by his parents for a well-child checkup. The parents are Amish and this is the first time their child has seen a doctor. His medical history is unknown, and he was born at 39 weeks gestation. His temperature is 98.3°F (36.8°C), blood pressure is 97/58 mmHg, pulse is 90/min, respirations are 23/min, and oxygen saturation is 99% on room air. The child is in the corner stacking blocks. He does not look the physician in the eye nor answer your questions. He continually tries to return to the blocks and becomes very upset when you move the blocks back to their storage space. The parents state that the child has not begun to speak and often exhibits similar behaviors with toy blocks he has at home. On occasion, they have observed him biting his elbows. Which of the following is the best next step in management?

Educating the parents about autism spectrum disorder

Restructuring of the home environment

A 3-month-old African American boy presents to his pediatrician’s office for his routine well visit. He was born full-term from an uncomplicated vaginal delivery. He is exclusively breastfeeding and not receiving any medications or supplements. Today, his parents report no issues or concerns with their child. He is lifting his head for brief periods and smiling. He has received only 2 hepatitis B vaccines. Which of the following is the correct advice for this patient’s parents?

He should start vitamin D supplementation.

He should have his serum lead level checked to screen for lead intoxication.

He needs a 3rd hepatitis B vaccine.

During the selection of subjects for a study on infantile vitamin deficiencies, a child is examined by the lead investigator. She is at the 75th percentile for head circumference and the 80th percentile for length and weight. She can lift her chest and shoulders up when in a prone position, but cannot roll over from a prone position. Her eyes follow objects past the midline. She coos and makes gurgling sounds. When the investigator strokes the sole of her foot, her big toe curls upward and there is fanning of her other toes. She makes a stepping motion when she is held upright and her feet are in contact with the examination table. Which of the following additional skills or behaviors would be expected in a healthy patient of this developmental age?

Cries when separated from her mother

Responds to calling of own name

A 6-month-old girl is brought to the physician for a well-child examination. She was born at 37 weeks' gestation. Pregnancy and the neonatal period were uncomplicated. The infant was exclusively breastfed and received vitamin D supplementation. She can sit unsupported and can transfer objects from one hand to the other. She babbles and is uncomfortable around strangers. She is at 40th percentile for length and at 35th percentile for weight. Vital signs are within normal limits. Physical examination shows no abnormalities. In addition to continuing breastfeeding, which of the following is the most appropriate recommendation at this time?

Introduce solid foods and continue vitamin D

Introduce solid foods and add vitamin C

Introduce solid foods and cow milk

A 4-week-old infant is brought to the physician by his mother because of blood-tinged stools for 3 days. He has also been passing whitish mucoid strings with the stools during this period. He was delivered at 38 weeks' gestation by lower segment transverse cesarean section because of a nonreassuring fetal heart rate. He was monitored in the intensive care unit for a day prior to being discharged. His 6-year-old brother was treated for viral gastroenteritis one week ago. The patient is exclusively breastfed. He is at the 50th percentile for height and 60th percentile for weight. He appears healthy and active. His vital signs are within normal limits. Examination shows a soft and nontender abdomen. The liver is palpated just below the right costal margin. The remainder of the examination shows no abnormalities. Test of the stool for occult blood is positive. A complete blood count and serum concentrations of electrolytes and creatinine are within the reference range. Which of the following is the most appropriate next step in management?

Continue breastfeeding and advise mother to avoid dairy and soy products

Perform stool antigen immunoassay

Perform an air enema on the infant

Assess for IgA (anti‑)tissue transglutaminase antibodies (tTG)

Stop breastfeeding and switch to soy-based formula

Introduction of complementary foods for USMLE Step 3: High-Yield Pediatrics Lessons

Timing & Readiness - The Starting Line

When to Start: Exclusively breastfeed until 6 months (180 days). Introduce complementary foods at 6 months, not before 4 months.
Key Developmental Readiness Cues:
- Good head and neck control; can sit upright with support.
- Loss of tongue-thrust (extrusion) reflex.
- Shows interest in food: opens mouth, leans forward for spoon.
- 📌 Mnemonic: HEADS → Head control, Extrusion reflex gone, Appetite for more, Developmental interest, Sits up.

⭐ For high-risk infants, introducing allergens (e.g., peanuts, eggs) between 4-6 months under guidance may ↓ allergy risk. Do not delay beyond 6 months.

Infant developmental readiness for solid foods

Age of Introduction: Start at 6 months alongside continued breastfeeding.
Initial Foods (6-7 months):
- Cereals: Begin with single-grain, iron-fortified cereals (e.g., rice, ragi).
- Purees: Introduce single-ingredient pureed vegetables (carrot, sweet potato) and fruits (apple, banana).
Key Principle: Introduce one new food every 3-5 days to monitor for allergies.

Baby food textures from pureed to minced

Texture Progression:

⭐ Early Allergen Introduction: Recent guidelines suggest introducing common allergenic foods (peanuts, eggs) between 6-12 months, after other solids are tolerated. This may ↓ the risk of developing food allergies.

⚠️ Foods to Avoid in 1st Year:
- Honey: Risk of infant botulism.
- Cow's Milk: As a primary drink.
- Added Salt & Sugar.
- Choking Hazards: Whole nuts, grapes.

Responsive Feeding - The How-To Guide

Core Principle: Feed on demand, responding to the child's hunger and satiety cues.
Cues to Recognize:
- Hunger: Opens mouth, leans for the spoon, excited.
- Satiety: Turns head away, pushes spoon, slows eating pace, spits out food.

Infant Hunger and Satiety Cues

⭐ Division of Responsibility (Ellyn Satter):

Parent/Caregiver decides: What, When, Where to eat.

Child decides: How much to eat, or whether to eat at all.

Best Practices:
- Encourage self-feeding when ready.
- Maintain eye contact; avoid distractions (e.g., screens).
- Be patient; never force-feed or bribe.

Problem Foods - Caution on a Spoon

Foods to avoid for infants under 1 year

Honey: Risk of infantile botulism (spores). Avoid until >1 year of age.
Cow's/Buffalo's Milk: As main drink, only after >1 year. Poor iron source, ↑renal solute load, risk of occult bleeding.
Hard/Round Foods: Choking hazard (e.g., whole nuts, grapes). Serve as puree, mash, or powder.
Added Salt & Sugar: Avoid. Immature kidneys (salt); risk of dental caries & unhealthy food preferences (sugar).

⭐ Cow's milk introduced before 1 year can lead to iron-deficiency anemia due to its low iron content, poor bioavailability, and potential for causing occult intestinal blood loss.

High‑Yield Points - ⚡ Biggest Takeaways

Exclusive breastfeeding is recommended for the first 6 months of life.

Complementary foods should be introduced at 6 months, alongside continued breastfeeding.

Start with single-grain cereals (like rice or suji); introduce new foods one at a time every 3-4 days.

Avoid honey in infants <1 year old due to the risk of infant botulism.

Cow's milk should not be given as a primary drink before 1 year of age.

By 1 year, the child should be consuming modified family pot-meals.

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