You may start to feel the baby moving around inside you now. These movements are becoming more coordinated. Your baby can hold his or her head erect, and the development of facial muscles allows for a variety of expressions such as squinting and frowning. Some new mothers don’t realize what they are feeling is actually the baby moving about.
Around the 16th to 18th week of pregnancy, your health care provider will likely offer you the maternal blood screening test, also known as a “triple marker” test or a “triple screen,” which measures the levels of alpha-fetoprotein (AFP) , a protein produced by the fetus, and the pregnancy hormones hCG and estriol in the mother’s blood. The results of the triple marker test can tell moms whether their babies are at risk for (not whether they have) neural tube defects such as spina bifida or chromosomal abnormalities such as Down syndrome.
Your baby is weighs about 2.8 ounces (80 grams) and measures about 4.6 inches (116 mm) in length. The ears have moved from the neck area to the head. Your baby is emptying her bladder about every 30-45 minutes now. The sex can now be determined by an ultrasound. More calcium is deposited on your baby’s bones as the skeleton continues to develop. Lastly, if your baby is female, millions of eggs, or ova, form in her ovaries this week.
Revision date: July 7, 2011
Last revised: by Janet A. Staessen, MD, PhD