Biology

Infant Developmental Milestones: High-Yield USMLE Points

When does a baby say its first words, Mama and Dada? When does a baby learn to stand up and walk on its own? Is it normal for an infant to develop stranger anxiety at 9 months? In this quick and easy-to-understand lesson, we review the infant developmental milestones at 1 month, 6 months, 9 months, 12 months, 2 years, 3 years, and 4 years. This lesson includes high-yield USMLE quick take-home points, high yield summaries, and practice test questions/answers on infant developmental milestones.

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At 1 month, the baby should reach the following main developmental milestones:

  • lift head
  • track with eyes
  • recognize parents
  • coo

Memory Aid: Think of the logic behind the order. Baby lifts its head. Eyes wander and then sees parents! Coos at (parents).

At 6 months, the baby should reach the following main developmental milestones:

  • sit up
  • raking grasp (using palm and fingers (not usually thumb) to move objects)
  • babbles (babble but can’t say Mama/words)
  • stranger anxiety (anxious around strangers who are not mama/dada/or familiar caretaker)

At 9 months, the infant should reach the following main developmental milestones:

  • walk with assistance
  • 3 finger grasp
  • Say words like Mama/dada
  • Wave bye-bye/patty cake

At 12 months, the infant should reach the following main developmental milestones:

  • walk with no assistance
  • 2 finger pincer grasp
  • Mama/Dada
  • Imitate parent

1-year-old who can’t walk is fine, but a 1-year-old who can’t sit up is worrisome.

This is a commonly tested point in USMLE. High-Yield. So if the vignette says a one-year-old is brought into the clinic and has not learned to sit up yet, then there is likely a medical problem!

At 2 years, the baby should reach the following main developmental milestones:

  • Climb 2 steps
  • 2 word phrases
  • Follows 2 step commands
  • Can stack 6 blocks (2+2+2=6)

At 3 years, the toddler should reach the following main developmental milestones:

  • Ride a tricycle
  • Make 3 word sentences (I like you!)
  • Brush teeth (think of a 3 multi-layered toothpaste!)
  • Draw a circle (3.14)
  • Can also draw a face with 3 parts (face, eyes, mouth)

4-year-olds should reach the following main developmental milestones:

  • Can hop on one leg (looks like a 4)
  • Copy a cross “+” (literally draw a cross)
  • Play with kids and have fun!

High-Yield USMLE Points: Infant Developmental Milestones – Summary Table and Mnemonics

TimelineInfant Developmental Milestones
1 monthLift own head
Track with eyes
Recognize parents
Coo
6 monthsSit up
Raking grasp (using palm and fingers (not usually thumb) to move objects)
Babbles (babble but can’t say Mama/words)
Stranger anxiety
9 monthsWalk with assistance
3 finger grasp (immature)
Say words like Mama/dada
Wave bye-bye/patty cake
1 year
Walk with no assistance
2 finger pincer grasp (mature) (pinch yourself)
Mama/Dada
Imitate parent
2 YearsClimb 2 steps
Can say 2 word phrases
Follow 2 step commands (Give me!)
Can stack 6 blocks (Add up all the above: 2+2+2=6)
3 YearsRide a tricycle
Make 3 word sentences (I like you!)
Brush teeth (think of a 3 multi-colored layer toothpaste!)
Draw a circle (3.14)
Can also draw a face with 3 parts (face, eyes, mouth)
4 YearsCan hop on one leg (looks like a 4)
Copy a cross “+” (literally draw a cross)
Play with kids and have fun!
Draw a Square

Practice Test Questions: Infant Developmental Milestones

Answers to the practice test questions are at the bottom of this article! Good luck!

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Answers to Practice Test Questions:

  1. 3 years old! The child is likely 3-years-old because he has reached developmental milestones for 3-year-olds including riding a tricycle and drawing a circle. The fact that he is not yet interested in playing with other kids is indicative that he is likely not a 4-year-old. 4-year-old are more likely to be interested in engaging group play, or playing with other kids, rather than by him/herself.
  2. Walk with no assistance. At 1 year, the baby ideally should know how to walk no assistance. August is 9 months old, so he/she should have already know how to sit up by him/herself and achieved new milestones, including waving bye-bye, grasping objects with 3 fingers.

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