At 12 weeks the baby is now about 2 ½ inches. It is moving a lot but it is not bog enough to feels the movements. The bones are now forming and can just now be seen on ultrasound. The kidneys are also starting to make urine.
At 12 weeks first trimester screening is available. This involves an ultrasound of the neck called nuchal translucency as well as blood tests. These tests are screening for genetic abnormalities bit they have a very high false positive rate. Many women decide not to do the first trimester screening, this is something you want to talk to your doctor about the pros and cons.
12 weeks is the time that chorionic villus sampling (CVS) can be done. This test involves placing a needle through either the abdomen or the vagina and taking a small piece of the placenta. This can then be tested for genetic abnormalities of the baby. It has a higher miscarriage rate and is less accurate than amniocentesis. The advantage is that it can be done at 12 weeks. Because the risk is less with people that do many of these, it is not available in all areas. CVS is typically performed in large medical centers. Ask your doctor about CVS and if it is available in your area. The availability of CVS may effect your decision about first trimester screening.
The kidneys are responsible for making urine. At 12 weeks the baby’s kidneys are just starting to make urine. The urine becomes the amniotic fluid. It surprises some people to hear that the baby spends most of its time in the uterus surrounded by urine. This is an important part of fetal development as it will be important for stimulating lung development.
The symptoms of early pregnancy are starting to improve for most women at 12 weeks. The breast tenderness is less, the fatigue is getting better, and for most women the nausea and vomiting is starting to improve.