You are now 17 weeks pregnant which is the beginning of week 18. Your baby measures about 19 cm long from head to toe (or 7.6 inches) and weighs about 280 grams (9.8 ounces). Many women elect to have a routine ultrasound between 18 to 20 weeks (usually at 19 weeks). Unborn babies need to be at least 18 weeksgestation for the ultrasonographer to clearly see the normal physical structures of their body, including their heart, lungs, kidneys, brain and spine. An experienced ultrasonographer may even be able to tell if your baby is a girl or a boy by this stage (although this is not always 100% accurate!)
Image 66-22 shows an unborn baby having an ultrasound at 18 to 20 weeks.
Your baby's skin is still fine, transparent and slightly wrinkled because they do not have a layer of fat yet. The many blood vessels flowing underneath their skin makes it appear purply-red. The scant whiskers of hair on various parts of your baby's body have now become a fine layer of down covering them all over (called 'lanugo'). This hair helps protect your baby's skin and is only shed a few weeks before they are due to be born.
Your baby will now explore their own body with their hands and if you are having twins or more they may try and locate each other, by touching and exploring the body of their brother or sister. There is plenty of fluid around your baby at this stage, allowing them to turn, twist and change position frequently. Some women definitely feel their baby move now (called 'quickening'), however for many others, this exciting event is not experienced until 20 to 22 weeks.