During week 23 of the pregnancy, the baby’s lungs develop rapidly beginning preparation for life on the outside. The lungs are beginning to produce a substance that lines the air sacs called surfactant. This substance allows the air sacs to inflate easily. It also keeps them from collapsing and sticking together when they deflate.
If your baby was born before this time, the lungs would have had no chance of working. Now it’s possible that the lungs could function to some degree outside the womb, however, your baby would need a lot more surfactant to handle breathing air without help. In addition, the blood vessels in your baby's lungs are growing and developing in preparation for breathing. He or she is making breathing movements, but these are just trial runs.
Your baby is still receiving oxygen through your placenta. There’s no air in the lungs until after birth. Although your baby now looks like a baby he or she is still slender and delicate looking, with little body fat and thin, nearly translucent skin. Later in your pregnancy when fat production catches up to skin production, your baby will grow into this skin and will look more like an infant. Babies born at 23 weeks can sometimes survive if they receive the appropriate medical care in a neonatal intensive care unit.
But complications are common and usually serious. On the bright side, the long-term outlook for premature babies is improving each year as knowledge in the field of neonatal medicine continues to expand. But there’s no doubt that at this age, baby is far better off staying in the uterus, if at all possible.
The baby can be felt through your abdominal wall and the midwife or doctor will palpate your abdomen to see how the baby is lying. You may occasionally feel a pain rather like a stitch down the side of your stomach. This is the uterine muscle stretching and it will go away after you have had a rest.
The baby is beginning to look as it will at birth, with the head more in proportion to the body. In a boy, the scrotum is now well developed and in a girl the ovaries already contain several million eggs. (These will reduce to around two million at birth and will carry on decreasing until puberty) The baby is around 11.4 inches (29 cm) long and weighs approximately 1.1 pound (501 grams)