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!

2nd 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.

Week 17 – your 2nd trimester

You might start to feel your baby move now. You will not be able to tell exactly what your baby's up to, but soon you could be feeling every kick, punch, hiccup and somersault.

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.

Around 1 in 10 women feel stressed or anxious during their pregnancy, and hormones can make even small problems feel overwhelming. If you feel sad or worried, talk to your doctor or midwife – there's a big support network out there for you.

Your baby's movements

Many women spot the first signs of their baby moving between 18 and 24 weeks. Inside your tummy, you might feel:

  • bubbling
  • fluttering
  • rolling

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 are relaxing

Tommy's has information about baby movements in pregnancy.

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. They usually fade to silver and become much less noticeable after your baby is born.

Read more about stretch marks on the NHS website.

2nd trimester pregnancy symptoms (at 17 weeks)

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

Your signs of pregnancy could include:

You may also experience symptoms from earlier weeks, such as:

Read Tommy's guide to common pregnancy 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.

Your baby can:

  • move their eyes, although they'll stay shut for now
  • react to loud noises
  • open and close their mouth

Your baby's fingernails are starting to grow and 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.

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 in a safe environment.

It's a good time to tone up your pelvic floor muscles. Gentle exercises can help to prevent leakage when you laugh, sneeze or cough. Get the muscles going by pretending that you're having a wee and then stopping midflow. Visit Tommy's for more ideas on 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.

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 tea, coffee and anything else with caffeine. Ask your midwife or GP for support if you need it.

To keep bones and muscles healthy, we need vitamin D. From late March/early April to the end of September, most people make enough vitamin D from sunlight on their skin. However, between October and early March, you should consider taking a daily vitamin D supplement because we cannot make enough from sunlight.

Some people should take a vitamin D supplement all year round, find out if this applies to you on the NHS website. You just need 10 micrograms (it's the same for grown-ups and kids). Check if you're entitled to free vitamins.

It's recommended that you do 150 minutes of exercise a week while pregnant. 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.

There's no need to eat for 2. 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.

You and your family should follow the government and NHS guidance on coronavirus (COVID-19):

  • read government guidance on how to stay safe from COVID-19
  • get NHS advice about COVID-19
  • use the NHS COVID-19 app for England and Wales – it's the fastest way of knowing when you've been exposed to COVID-19
  • To find out about about COVID-19 and pregnancy, childbirth and breastfeeding, have a look at advice on the:

  • NHS website
  • Breastfeeding Network
  • World Health Organization
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