Weekly Guide to Pregnancy: Week 16
How big is my baby?
This week your baby is approximately 11-12cm (4.3-4.6 inches) long and weighs about 80 grams (2.8 ounces).
All embryos start off looking much the same, as far as outward appearances are concerned, but this week sexual differentiation is more definite. Your baby's legs are now longer than it's arms, and they are moving around. It may be possible to feel your baby move (described as "quickening") but don't worry if you haven't felt movement yet - it will happen some time between week 16 and week 20.
What pregnancy symptoms will I be experiencing?
You may start to feel the baby move from now (termed quickening), although this is more common in women who have had previous children. The majority of women will start to feel movements some time between Week 16 and Week 20. The baby's movements are described by many women as a "flutter". Some women will say that it took a little while for them to realise that they were feeling the flutter.
If you are healthy, under 35 and have no hereditary or genetic problems in your family, it is unlikely you will need to undergo any of the special pregnancy tests. There are a number of special tests that may / can be performed:
if you request them
if your doctor suspects there is a problem, or
if you are over a certain age
Modern testing enables the early detection of abnormalities for those considered to be in a risk category. Early detection of serious abnormalities gives you the opportunity to decide whether or not to progress with your pregnancy. Two of the special tests that can be performed at around Week 16 are:
AFP Test - this is a blood test that may be performed at around Week 16 to screen for an increased risk of neural tube defect, or spina bifida (an abnormality in the formation of the spine). The test measures the level of alpha-fetoprotein, a protein manufactured in the baby's liver, which then passes into your bloodstream. A high level of AFP in your blood can indicate a neural tube defect. Too much AFP in the blood occurs in three in 100 women, but don't panic because there can also be other reasons for high AFP levels. It might mean that you are having twins, or that your pregnancy is further along than you thought. It doesn't necessarily mean the baby is affected, but it will probably be suggested that you have an amniocentesis for more definite results. If, on the other hand, your AFP level is very low (this happens in less than five in 100 pregnancies), the levels of two other hormones may also be measured. This is called a triple screening (see below).
Triple Screen Test / The Bart's Test - this test is a triple blood test that can be performed at around Week 16 to screen maternal blood for evidence of an increased risk of Down's syndrome or other chromosomal abnormalities. The test measures AFP, hCG and oestriol levels. If the result shows a high risk then you can decide whether to have an amniocentesis.
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