Developmental Standards for a 3-Month-Old Baby

The developmental standards for a three-month-old baby mainly include an average weight of approximately 6.93 kg for male infants and 6.24 kg for female infants.

The average length for male infants is about 63.35 cm, while for female infants it's about 61.53 cm. The average head circumference for male infants is about 41.25 cm, compared to 39.90 cm for female infants. The average chest circumference for male infants is around 41.75 cm, versus 40.05 cm for female infants. Head circumference growth is an important indicator of brain development, with ranges of 39.4-41.0 cm for males and 38.2-39.6 cm for females.

In terms of motor skills, the baby can steadily lift their head and turn it from side to side. When supported in a sitting position, the head no longer tilts backward. The baby starts attempting to roll over and can move the body by kicking legs. Hand movements become more coordinated, enabling the baby to grasp toys hanging in front of them. The infant also shows increased sensitivity to sounds and light, can track moving objects, demonstrates clear interest in human faces, and begins trying to imitate facial expressions.

At this stage, the baby can support themselves on their elbows while lying on their stomach and lift their head at an angle greater than 45 degrees. They can hold their head steady when in a vertical position and can move from lying on their back to a side-lying position. The baby can touch objects with their hands, grasp items and shake them, and sometimes bring both hands together. Social smiling begins to emerge, meaning the baby smiles at people rather than inanimate objects, and shows increased attention and pleasure in response to familiar voices and faces.