3 Month Old Baby: Developmental Milestones

Your three-month-old is gradually getting bigger and stronger day by day, showing development in his motor, communication, and other skills. Here is what you can expect from your baby as he steps into the third month of his life.

Physical development

Growth Details Boys Girls
How much should a 3-month-old weigh 11.24 to 17.41 pounds [6] 10.14 to 16.31 pounds [35]
What should the height of a 3-month-old be 22.67 to 25.70 inches [6] 21.96 cm to 25.11 inches [35]
How much should their head size be (97 percentile babies) [21] 15.07 to 16.81 inches [6] 14.64 to 16.49 inches [35]
What is the respiratory rate of a 3 month-old [22] 30 to 45 breaths per minute 30 to 45 breaths per minute
What is the heart rate of a 3-month-old [22] 90 to 120 beats per minute 90 to 120 beats per minute

What should your baby be doing at 3 months

Motor skills

Your infant has an improved neck and head strength by this time, being able to lift as well as hold his head for a longer period during tummy time [1]. In fact, this is a crucial point in his life as he will be rolling over in a month’s time [2]. Because of an improved hand-eye coordination, he starts using both his hands [3], also attempting to reach out and swipe at toys dangling above him to bring them close [1,3].  Quivering of the chin, seen in newborns as his nervous system is in the process of developing, disappears by the third or fourth month [19].


In this month, the startle or Moro reflex starts fading gradually or goes away for good [1]. The tonic reflex also starts diminishing by now [4].


Psychiatrist Margaret Mahler refers to this three-month phase as hatching because the baby comes out of his shell, starting to interact as well as connect with his surroundings. Crying, which was his prime mode of expressing his feelings gets replaced by a lot of cooing and babbling sounds through which the baby may try communicating [1]. Some may even attempt to blow bubbles. Learning to acknowledge things, he will smile for a reason [1], with a few of them, even laughing out for the first time [33].

Cognitive development

As his brain is maturing, he can do a lot of things he was unable to do in the previous months. He is to some extent able to understand the cause of certain actions, thus reacting appropriately to it, like displaying his happiness by laughing when taken for an outing. He even enjoys seeing his reflection in the mirror [11, 12].


At this age, some babies may successfully cut their first tooth, displaying a lot of teething symptoms like excessive saliva secretion or drooling, biting and rashes [15].

 Sensory development


Your baby’s tracking ability progresses as the control of his eye muscles get better [3]. His preference for bright-colored objects continues, and your three-month-old would love observing human faces, staring back at you if you look at him [1].

Hearing skills

Infants at this stage show a lot of development as far as their auditory skill is concerned. Being able to recognize their mother’s voice, they acknowledge her presence by smiling [10]. They are even fond of music [1].

 How much should a 3-month-old eat

In the third month, he will drink approximately 5 ounces of milk, 6 to 8 times every day [7]. A formula fed baby should be given two and a half ounces per pound of his weight daily. If the baby weighs 6 pounds, then 15 ounces of milk is to be provided in a period of twenty-four hours. However, make sure that the intake of formula milk does not exceed 32 ounces [8]. It is also not recommended to give your three-month-old solid food.

In this month, your baby may go through a growth spurt resulting in rapid increase of height and weight, thus making them remain hungry right after a feed [9].

Sleep schedule

Showing a much-improved sleep pattern, your baby will sleep for about 15 hours daily including his night’s sleep as well as daytime naps [5].

Bowel Movements

By this time, their bowel movements are more stable as most of them pass stool every other day, and some may even clear their bowel many times in a day [16].

When to call a doctor

  • Persistent coughing along with a body temperature above 101.4°F, also displaying symptoms such as flushed cheeks, restlessness and a reduced appetite [17,18].
  • Irregularity in bowel movements or hardness in stool texture [20]. The presence of mucus or blood in his stool is also a matter of concern [32].
  • If the baby has an attack of diarrhea, passing runny or watery stool of yellow, brown or green color for more than two days or wetting over three diarrhea-filled nappies each day [32].
  • Nose bleeding persisting for more than ten minutes or causing breathing difficulties and fever [31].
  • Baby is vomiting a lot and showing symptoms such as a bulging fontanelle, decreased appetite, swollen abdomen, rash, and irritability [26].

Cradle cap, characterized by dandruff-like flaking skin on your baby’s scalp [24], and thrush or yeast infection, causing a white coating on his tongue  and mouth [27], are common at this stage of life. They should go away on their own within a few weeks [25, 34]. Consult your doctor in case your baby shows signs of distress like difficulty feeding due to the thrush.


5-in-1 vaccine (DTaP/Hib/IPV): The second dose of this vaccine is given in the third month [14].

Side effects of this vaccine include redness and pain in the injected area, restlessness, crying and fever [29].

Meningitis C: The first dose of Men C vaccine is at three months. The purpose of this shot is to protect the body against infection caused by meningococcal group C bacteria that lead to meningitis and septicemia [13].

The common side effects are redness and swelling of the vaccinated area, vomiting, mild fever and diarrhea [30].


  1. http://www.webmd.com/parenting/baby/baby-development-3-months
  2. http://www.babycentre.co.uk/a718/your-three-month-olds-development
  3. http://www.nlm.nih.gov/medlineplus/ency/article/002004.htm
  4. http://library.med.utah.edu/pedineurologicexam/html/03month.html
  5. http://www.babycenter.com/0_baby-sleep-basics-3-to-6-months_7656.bc
  6. http://www.babycenter.in/a1052194/baby-boys-growth-chart-0-to-12-months
  7. http://www.parents.com/baby/feeding/solid-foods/feeding-portions-menu/#
  8. http://www.babycenter.com/0_how-to-tell-how-much-formula-your-baby-needs_9136.bc
  9. http://www.babycentre.co.uk/a25012757/baby-growth-spurts
  10. http://www.babycentre.co.uk/a6509/developmental-milestones-hearing
  11. http://www.babycentre.co.uk/a1047257/understanding-your-babys-cognitive-development
  12. http://www.webmd.com/parenting/baby/tc/cognitive-development-ages-1-to-12-months-topic-overview
  13. http://www.nhs.uk/conditions/vaccinations/pages/vaccination-schedule-age-checklist.aspx
  14. http://www.babycentre.co.uk/a1011669/immunisations-chart
  15. http://www.whattoexpect.com/first-year/teething/
  16. http://www.parenting.com/article/my-baby-goes-a-long-time-without-pooping–what-do-i-do
  17. http://www.mayoclinic.org/diseases-conditions/common-cold-in-babies/basics/symptoms/con-20033841
  18. http://www.babycenter.com/0_fever-in-babies_84.bc
  19. http://www.medhelp.org/posts/Undiagnosed-Symptoms/Lower-jaw-quivering-in-infant/show/201021
  20. http://www.babycenter.com/0_constipation-in-babies_79.bc
  21. http://www.cdc.gov/growthcharts/html_charts/hcageinf.htm
  22.  http://www.emedicinehealth.com/pediatric_vital_signs/article_em.htm
  23. http://www.babycenter.com/0_hair-loss-in-babies_85.bc
  24. http://www.babycentre.co.uk/a80/cradle-cap
  25. http://www.nhs.uk/conditions/cradle-cap/Pages/Introduction.aspx
  26. http://www.babycentre.co.uk/a536689/vomiting-whats-normal-and-whats-not
  27. http://www.nhs.uk/Conditions/Oral-thrush—babies/Pages/Introduction.aspx
  28. http://www.seattlechildrens.org/medical-conditions/symptom-index/vomiting/
  29. http://www.nhs.uk/conditions/vaccinations/pages/5-in-1-vaccine-side-effects.aspx
  30. http://www.nhs.uk/conditions/vaccinations/pages/men-c-vaccine-side-effects.aspx
  31. http://www.uofmmedicalcenter.org/healthlibrary/Article/511620EN
  32. http://www.babycenter.com/0_baby-poop-a-complete-guide_10319333.bc
  33. http://www.whattoexpect.com/first-year/first-laugh/
  34. http://www.babycenter.com/0_thrush-in-babies_92.bc
  35. http://www.babycenter.in/a1052197/baby-girls-growth-chart-0-to-12-months [/ref]