Week-by-week guide to pregnancy

group of pregnant women
When you're pregnant, you have lots of questions. Our week-by-week pregnancy guide is packed with lots of useful information. From what's happening inside your body, to how your baby is developing, and tips and advice on having a healthy pregnancy – this is your one-stop pregnancy guide!

Second trimester

Our week-by-week pregnancy guide is full of essential information. From staying fit in pregnancy to advice on your maternity rights, you'll find it all here. Happy reading!

Week 16 – your second trimester

Big things are happening. Your baby is growing quickly and about to undergo another massive growth spurt. You will probably have put on some weight over the past few weeks (2 to 4kg) but that's just a guide, as every pregnancy is different.

What's happening in my body?

You'll probably see a midwife around now, who'll weigh you and talk to you about how you're getting on. You might get to hear your baby's heartbeat for the first time. You will also get the results of any blood tests that you had at your booking appointment, which could reveal everything from your blood type to whether your iron levels are low.

You will probably have been offered a test for three infectious diseases: HIV, hepatitis B and syphilis. If an infection has been picked up, then your midwife or doctor will talk to you about the best ways to protect your health and reduce the risk of passing on the infection to your baby.

Your blood pressure will be checked and you'll pee into a tiny cup to give a urine sample. This will be checked for signs of protein that could show if you're at risk of developing a dangerous condition called pre-eclampsia.

Hang loose – easing constipation

Constipation is common in early pregnancy. It's when you find it really hard to poo - and this can make you feel bloated, sick and give you tummy ache.

Try to:

  • eat foods that are high in fibre, such as wholemeal bread, fruit and veg, beans and lentils.
  • exercise regularly.
  • drink lots of water.
  • avoid iron supplements (but talk to your doctor or midwife before ditching any medication).

Read more about easing constipation in pregnancy.

Carbon monoxide alert

You can't see, smell or taste it – but carbon monoxide gas is a killer. You can come into contact with it through faulty or poorly ventilated cooking or heating appliances. If you've already got a carbon monoxide detector, then check that it's working. There's usually a 'test' button – if it doesn't beep, the battery's gone or you need a new detector. You can pick one up at most supermarkets. You can also become exposed to this harmful gas through breathing in cigarette smoke. If you're a smoker, or anyone in your house smokes, then this could be putting your baby's development at risk. We know how hard it is to quit, but there's help out there. Ask your doctor or midwife for support.

Second trimester pregnancy symptoms (at 16 weeks)

Everyone's pregnancy is different but if you feel unwell and it's getting you down, speak to your doctor or midwife.

Your signs of pregnancy could include:

  • swollen and bleeding gums
  • pains on the side of your belly, caused by your expanding womb (known as 'round ligament pains')
  • headaches
  • nosebleeds
  • bloating and constipation
  • indigestion and heartburn
  • sore breasts
  • leg cramps
  • feeling hot
  • dizziness
  • swollen hands and feet
  • urine infections
  • vaginal infections
  • darkened skin on your face or brown patches – this is known as chloasma or the 'mask of pregnancy'
  • greasier, spotty skin
  • thicker and shinier hair
  • symptoms from earlier weeks, such as morning sickness, weird pregnancy cravings, a heightened sense of smell, mood swings, a white milky pregnancy discharge from your vagina and light spotting (seek medical advice for any bleeding)

Tommy's, the baby charity, has a further list of common symptoms.

What does my baby look like?

Your baby, or foetus, is around 11.6cm long from head to bottom, which is the size of an avocado. The weight is around 100g, which is the same as a medium bag of salad.

Your baby is starting to pull faces now, but any smiling or frowning will be completely random, as there's no muscle control yet.

The nervous system continues to develop, and this enables your baby to start moving their arms and legs. You might be able to feel your baby kicking from next week onwards, which is something exciting to look forward to.

Your baby's hands can form fists and they may start punching around inside you too.

Action stations

This is a good week for planning and getting things done. Make a 'to do' list and start ticking things off – it's amazingly therapeutic. Put 'me time' on the list, in case you forget that you're important too.

This week you could also...

Many women will tell their employer after they've had their first pregnancy scan at around 12 weeks. Once you tell your employer, you have maternity rights and can attend antenatal appointments during paid work time. You can also ask for a risk assessment of your workplace to ensure that you're working in a safe environment.

It's a good time to tone up those muscles 'down under'. Gentle exercises can help to prevent leakage when you laugh, sneeze, cough or jump around on your future baby's trampoline. Get the muscles going by pretending that you're having a wee and then stop the 'urine' in midflow. Visit Tommy's for more ideas about pelvic floor exercises.

Ask your midwife or doctor about online antenatal classes – they may be able to recommend one. The charity Tommy's has lots of useful information on antenatal classes and preparing you for birth.

Ask your partner if they would like to take part in the antenatal classes. Even if you've had children before, they're still worth going to as you can meet other parents-to-be. The NCT offers online antenatal classes with small groups of people that live locally to you.

Do your best to stop smoking, give up alcohol and go easy on the cappuccinos. We know that's easy to say but hard to do. Ask your midwife or GP for support.

We can usually get enough vitamin D from sunlight, but between October and March it's best to take a vitamin D supplement every day. Just 10 micrograms is all you need (it's the same for grown-ups and kids). It's worth checking if you're entitled tofree vitamins.

Get moving! It's recommended that pregnant women do 150 minutes of exercise throughout the week. You could start off with just 10 minutes of daily exercise - perhaps take a brisk walk outside. Check out Sport England's #StayInWorkOut online exercises (scroll to the pregnancy section). Listen to your body and do what feels right for you.

Don't eat for two! Eat for you. You don't need any extra calories until the third trimester, which starts in week 28. Try to eat healthily, with plenty of fresh fruit and veg, and avoid processed, fatty and salty foods. You may be able to get free milk, fruit and veg through the Healthy Start scheme.

This week's treat

As you get bigger, you'll spend more time with your feet up, so find a good book to keep you company. Check out your nearest library to see if there are any details of antenatal classes and clubs to join when your baby's born.

Go back to week 15

Go to week 17

Sign up now for our pregnancy, baby and toddler guide

Get personalised emails for trusted NHS advice, videos and tips on your pregnancy week by week, birth and parenthood.

Get weekly emails