At 12 weeks your baby is around 6cm (2¼”) long and weighs about 15g (half an ounce). This week is a bit of a milestone for your baby – by now, he or she is fully formed with everything in place, and the only job left is to grow and mature all those muscles, bones and organs.
Until now, your baby's skeleton has been made of cartilage (the flexible tissue found in the ears and the tip of the nose). Around now, it begins the process of hardening into bone.
You’re probably starting to feel good (or at least better!) now – the pregnancy nausea may be wearing off, you might not feel quite so tired, and the frequent loo visits and mood swings may have settled down.
And you should feel good - you've made it to end of the first trimester! This is a great reason to celebrate – after all, you're past the greatest risk of miscarriage now, and your baby is well established and growing rapidly. (Not to mention that this is the last week you'll have to remember to take those folic acid supplements!)
As you start to feel better and more energetic, it's a great idea to put some of that energy to good use by getting some regular exercise. Don't worry – mild to moderate exercise is just as good for your baby as it is for you!
For more advice on exercising during pregnancy, visit the NHS website.