By the end of your second trimester into the beginning of your third, your baby has developed enough to survive -- with medical intervention -- outside of your womb. Between the 22nd and 27th week, your baby changes in appearance. She goes through rapid brain and central nervous system development, begins to have sleep-wake cycles and builds up the basic structures for breathing.
Between 22 and 27 weeks your baby is starting to look more like a newborn than a translucent, amphibian-like creature. He already has a fine fur-like coating on his head -- and all over his body for that matter -- and starts to grow real hair around the 24-week mark. Your baby's eyebrows and eyelashes are also becoming more noticeable during this time. He's gaining inches and pounds, topping off at up to 14 inches long and 2 1/4 pounds.
The Brain Builds
Around this time, your baby's brain is growing and building connections with her nervous system. This allows her to control some basic functions and respond to certain stimuli. For example, your baby can hear noises and move in response to them. As your baby's central nervous system becomes more complex, she begins to sleep and wake in cycles.
Breathing and Baby's Lungs
Even though your baby's lungs -- like his other major organs -- have already begun to develop, during the 22- to 27-week period, lung growth becomes more complex. For example, the air sacs inside of the lungs begin to form during the end of the second trimester. Although your baby isn't able to breathe on his own yet, his lungs are preparing for this stage.
In the event that you go into premature labor during the 22- to 27-week period, your baby has a more than fair chance of survival. While she isn't done developing, the end of the second trimester is the earliest possible time that your baby can live outside of you. Roughly eight out of every 10 babies born at this time survive with the assistance of medical technology.