20 weeks gestation 17 weeks gestation Your baby is anywhere from 4.4 to 4.8 inches by pregnancy week 17 and weighs almost 3 ½ ounces. He or she would fit nicely into the palm of your hand if you were able to hold them. At this stage, the baby should be able to start hearing things and should start to put on tiny layers of fat from this week on. Some women may notice the baby moving between 17 and 20 weeks, as it will become increasingly active. Between 18 and 19 weeks, the baby should measure between 5-7 inches and many abnormalities can now be picked up by ultrasound. An anomoly scan (major scan for detecting any defects) is usually carried out between 18 and 22 weeks. By 19-20 weeks the baby will start to produce meconium, the baby's first bowel movement,and the womb can be felt just below the belly button. The sex can almost certanly be determined by ultrasound at this point although it depends very much on the position of the baby! At this stage, the womb is rapidly growing and a woman may feel a little off balance and lighheaded. This is quite common and a pregnant mother should may sure she eats sensibly and drinks plenty of fluids.Rest is very important too, as is light excercise like walking By pregnancy 20 weeks the baby is now practicing breathing and swallowing regularly. Your baby continues to grow and fill out, with the head becoming slightly more proportional to the rest of the body.