Your 9 months Pregnancy You’re 21 weeks pregnant You’re now in the 21st week of your pregnancy, so here’s what your baby is doing 1 of Ad break How big is you baby?Your baby is around 18cm long (about the size of a large banana) and approximately 300g in weight. The extra weight your baby has been putting on will help to keep him warm after he’s born.Now find out how your baby has been growing… How is your baby growing?He’ll be swallowing lots of amniotic fluid. This is completely natural and is good practice for his digestive system. At this stage your baby's face may already have recognisable family features. The growth of his brain is rapid and it’s thought that it's around now his memory starts to develop, so if you play soothing music to him by this time, these familiar sounds may soothe your baby after he’s born. He already has a high number of red blood cells and now he’s also producing white blood cells. These are essential to help him fight infection. Now find out what’s happening to your body… What’s happening to your body?Your placenta is vital for your baby’s continued wellbeing and growth in the womb. It consists of a network of arteries and veins and at birth it weighs approximately one-sixth of the weight of your baby. It’s usually situated out of the way of the cervix in the lower part of your uterus, but your 20-week scan may have shown that it’s low lying. This isn’t anything to worry about at this stage as the majority of placentas move upwards before the baby is born. If your 20 week scan does show your placenta to be low-lying, you will be given another scan nearer birth. In about 1% of pregnancies, the placenta has not moved and blocks the way for the baby to come out. In these cases you’ll be given a caesarean. Learn more about what symptoms to expect this week and check out our week by week pregnancy guide... Find out what your baby was doing in week 20 of your pregnancy and what happens when you’re 22 weeks pregnant. By Sara Mackenzie Comments Latest on MadeForMums Must-have toys for Christmas from the biggest sellers Why e-books might be better for your toddler than paper ones Toddler wets herself after being blocked from using toilet on plane Could these be Beyonce and Jay-Z's twin baby names?