You will start feeling properly pregnant, be enjoying your new and growing bump and hopefully are past any early feelings of tiredness and nausea. Many pregnant women experience a surge of energy during their second trimester.
Your baby now tips the scales at around 50g – two whole ounces. A fine covering of downy hair over your baby's body has an insulating effect as well as providing a waterproof coating. Hearing continues to develop this week as the tiny bones of the inner ear start to harden. Hair and nails are growing too. Rapid growth means a crown-to-rump length of 10cm, which is about four inches.
On the outside
If you feel like you've put on more weight than the mere two ounces contributed by your baby, don't fret. Your placenta plus your amniotic sac and the fluid that's inside it will account for around half of your total pregnancy weight gain – and given that they're fully developed long before your baby has finished growing, you'll notice the extra weight much earlier.
You have more blood circulating around your system than ever before, and this will contribute to a bit of weight gain, as will the water retention some women experience in pregnancy.
If you've been laid low with a cough or cold you can blame your hormones again. Your pregnancy alters your immune system making you more susceptible to viruses.
If you're feeling tired, exercise will help boost your energy levels. You can continue doing whatever you usually enjoy (as long as you avoid vigorous contact sports and dangerous activities) although it's probably best not to take up something new just in case. Swimming is brilliant all-round exercise and you'll appreciate that sense of weightlessness more and more as you gain in weight; brisk walking is also energising or you might find your local leisure centre offers special exercise classes for pregnancy.
Things to think about
If you've been offered amniocentesis (a diagnostic test to check for abnormalities including Down's syndrome and spina bifida, plus other serious health conditions) you will need to make a final decision. Try not to worry too much: the test itself is more uncomfortable than painful, but carries a risk of miscarriage (around 1%). If you're undecided, contact ARC (Antenatal Results and Choices), a national charity which provides impartial support and information throughout and after the antenatal screening and testing process. Find out more about antenatal tests.