Your baby-to-be's favorite position is the familiar C shape with her legs tucked into her chest and her head pulled toward her knees. She might occasionally stretch out of this position in utero and test out her strengthening muscles. And you'll most likely feel it!
Other changes that you won't feel are happening deep within your unborn baby's bones. For the past week, your baby's bones have begun producing fetal red blood cells. Previously, the baby's liver and spleen were responsible for this job, but as the bones mature, they will be able to sustain your baby's red blood cell needs. By week 30, the spleen will stop producing red blood cells, and a few weeks before birth, the liver will stop, too.
The byproduct of red blood cell production is a substance called bilirubin. Your unborn baby's liver is working to help pass bilirubin through the umbilical cord and on to the placenta, where your liver takes care of the excess. At birth, her liver might or might not be ready to take over the job of removing all the bilirubin from her system. Often, a newborn's body needs a few days to make the adjustment to removing all the bilirubin produced by her body's red blood cell production. Another reason bilirubin often builds up in infants is that their bodies produce more red blood cells than adults. A bilirubin buildup leads to jaundice, a condition where your newborn's skin and eyes appear tinted yellow. The condition is often treated with time in the sun, called phototherapy. More severe jaundice may be treated with a blood transfusion. If left untreated, jaundice can lead to brain damage, deafness, and other serious problems. Your health care provider will test your infant's bilirubin levels through a physical evaluation as well as a blood test.
Above his eyes, his eyebrows are taking shape and the hair on his head is growing. It will take weeks, though, for your baby to grow a full head of hair.
Terms to Know
Bilirubin: A yellowish pigment that is left over from the production of red blood cells in the body. The liver disposes of bilirubin through bile that passes through the intestines and then is excreted in urine or stools.
Jaundice: A common condition among newborns where the liver does not remove all the bilirubin from the bloodstream, leading to a yellowing of the skin and eyes. In mild cases, jaundice is often treated with phototherapy, or time in direct sunlight. Signs of jaundice do not usually occur for one to two days after birth.
Important Information About Your Pregnancy
- Learn more about your baby in the second trimester.
- Discover more about your 22nd week of pregnancy.
- Sign up for your personal pregnancy calendar!
- Read about your previous week of pregnancy.
- Learn what to expect during your next week of pregnancy.
Copyright © 2010 Meredith Corporation.
Images courtesy of the American Institute of Ultrasound in Medicine (AIUM.org).