23-26 weeks gestational age
His muscles are developing, making his movements more powerful. His lungs are getting ready for breathing. He has a strong grip. He has an early form of memory. He can weigh from 14 ounces to almost 3 pounds, and measure 11-16 inches in length. He is practicing the movements that will help him eat, drink and breathe.
In weeks 24 and 25, neurons (cells that conduct nerve impulses) migrate to different levels of his brain, which will help him to make connections after birth. His cognitive and sensory development progresses, with an enhanced sense of touch and hearing, denoted by a growing familiarity with a variety of sounds. Furthermore, he will start to experience an early form of learning and memory, called Habituation.
Your baby's movements are becoming more pronounced. By this stage, he should be rolling, tumbling and kicking in the womb. He is gaining weight, becoming stronger and developing motor skills. Depending on his rate of growth and size, his movements will slow down toward the end of the 3rd trimester, when he has less space in which to move. His sleep habits may not match your own.
Sensory Development and Habituation (Tuning out the Environment)
Your baby is learning the art of Habituation, one of the simplest forms of memory that consists of “tuning out” the surrounding environment. He will continue to develop this skill after birth, which will allow him to sleep through familiar noises, such as a fan or street noise. By week 24, your baby's sense of hearing is well established.
Lung Development and First Breaths
At this stage, your baby's lungs do not function as he is receiving his oxygen from you. However, in preparation for breathing, his lungs start to produce a fatty substance called surfactant, which covers the inner lining of his air sacs. Surfactant will allow his lungs to expand more easily when he is required to breathe on his own.