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 17 – your second trimester

It could just be wind – but those funny feelings in your belly might be your baby moving. This is a major milestone and a highlight of many pregnancies. Right now, you won't be able to tell exactly what your baby's up to. But soon you could be feeling every kick, punch, hiccup and somersault.

There's lots more happening this week too…

What's happening in my body?

Week by week, your baby's getting bigger, and so is your placenta, which is feeding your baby and also removing waste. By the end of your pregnancy the placenta will weigh around 500g, which is as heavy as a packet of pasta.

Your waist will start to vanish as your womb moves up and out of your pelvis. This will make you look more obviously 'pregnant' and, with any luck, you'll start to 'bloom' too. Many women look and feel amazing when they're pregnant. They have glossy, full hair (as hair loss is slowed down) and radiant skin (caused by a boost in blood volume and hormones).

However, everyone's different, and some women feel unattractive and overwhelmed by their changing body, the responsibility of having a baby and the strain it can put on relationships. Around 1 in 10 women feel stressed or anxious during their pregnancy, and your hormones can make even small problems feel so much worse than they really are. If you feel sad or worried, then talk to your doctor or midwife – there's a big support network out there for you.

A moving experience

Have you felt your baby move yet? Many women spot the first signs of movement at 18 to 20 weeks, but it could be earlier than this.

Inside your baby belly, you might feel:

  • bubbling
  • fluttering
  • rolling

This is known as 'quickening' and it's a reassuring sign that your baby is thriving. In a few weeks, the signs will be much more obvious. You might even be able to tell the difference between punching and kicking. Don't worry, it doesn't hurt, it just takes you by surprise, and it's very strange to see your belly move as a little foot kicks out!

Share the experience with your partner and let them place their hand on your bump when the baby's moving.

You might find that your baby moves more…

  • after meals
  • when you listen to loud music
  • when you rub your tummy and talk to your baby
  • when you really, really want to go to sleep!

See if you can work out any patterns. You can watch a video about what to look out for here.

Stressed by stretch marks?

At some point, you might notice red or purple streaks over your stomach and breasts. You could also spot them on your bottom and thighs. These are stretch marks and affect up to 8 in 10 women. They are usually caused by hormones and your skin stretching more quickly than it would like to. They usually fade to silver and become much less noticeable in the months after the baby's born. You can buy all kinds of 'miracle' creams, but your best bet is to gently apply an unscented moisturiser when the lines appear… and wait for time to work its magic. Read more about stretch marks.

Second trimester pregnancy symptoms (at 17 weeks)

You may be getting a few pains and niggles as your bump gets bigger. Your symptoms should be manageable, and if they're not, talk to your doctor or midwife.

Your signs of pregnancy could include:

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

What does my baby look like?

Your baby, or foetus, is around 12cm long, from head to bottom, and weighs around 150g. That's roughly the size of a pomegranate and the weight of a ball of mozzarella. The baby's skin is wrinkled and there's a lot of fattening up to do. By the end of your pregnancy, your little one will be much plumper and will fit into their skin better, although they may still come out looking rather creased.

The big news of the week is that you may start to feel your baby move.


  • your baby's eyes can move, although they'll stay shut for now
  • they can react to loud noises
  • their mouth can open and close
  • fingernails are starting to grow

Your baby will have their own unique fingerprints. Even identical twins have different fingerprints.

Action stations

Have you decided where you'd like to give birth? Read more about choosing a hospital, midwife-led unit or home birth. Talk to your doctor or midwife about your local options. It's a big decision but you can always change your mind later.

This week you could also…

You don't have to tell your employer for several more weeks, but as soon as you do, you will have maternity rights and can attend antenatal appointments during paid work time. You can also ask for a risk assessment of your work place to ensure that you're working away 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 baby's future 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.

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 as we are at home a lot more at the moment, you may not be getting enough. If you're pregnant, or breastfeeding, you should consider taking a daily vitamin D supplement. It's worth checking if you're entitled to free 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

Enjoy a soothing head massage. You don't need special oils - just ask your partner or a family member to gently massage your scalp and neck while you sit upright on a chair. Research shows that regular head massages can reduce headaches by easing stress and relaxing the muscles that go into spasm.

If you get really painful headaches, then talk to your midwife or doctor, just in case there's an underlying problem.

Go back to week 16

Go to week 18

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