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 21 – your 2nd trimester

As you start the 2nd half of your pregnancy, you'll be entering a period of rapid growth. Your baby is getting ready for life outside the womb and developing essential skills including sucking and breathing.

What's happening in my body?

You may start feeling a little unsteady as your bump gets bigger. This is because your center of gravity has changed and your joints are looser. If you have a tumble, try not to panic as your baby is well protected, but do let your midwife know as soon as possible. If you travel on public transport, think about getting a baby on board badge to prompt other commuters to give up their seats.

Your baby is moving around a lot now, and establishing waking and sleeping patterns. The only trouble is, your baby may be wide awake when you are ready to sleep. Have naps when you can to make up for lost sleep at night. Read more sleep tips.

Dump the junk food

A healthy diet, with lots of fresh fruit and veg, will give you more energy than junk food. Research shows that if you eat well, your baby will too, and you're both less likely to get conditions like diabetes.

Try to eat 5 portions of fruit and veg a day, and go for wholegrain, low-fat and low-sugar options when you're given the choice. Here are some easy recipes.

Simple food swaps

Swap takeaways for healthier and tastier homemade alternatives. Try these recipes:

2nd trimester pregnancy symptoms (at 21 weeks)

This week, 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 26.7cm long from head to toe, and weighs about 350g. That's approximately the size of a carrot, and the weight of 5 pitta breads.

Your baby is now heavier than the placenta. The placenta basically doubles up as a larder and toilet, by providing food and removing waste. It will keep on growing during your pregnancy to do its vital work.

Meanwhile your baby has been developing a fine, downy layer of hair called "lanugo" – the purpose of this fur coat is probably to keep your baby at the perfect temperature, and it usually vanishes before the birth. Your baby is also developing hair and eyebrows.

Your baby can now hear noises and voices outside the womb. If you sing to your bump, no matter how bad it sounds, they will be your biggest fan.

Action stations

Pregnancy can be a happy time, but for some it's stressful and there are lots of difficult decisions to make. If you were given any unexpected news at your anomaly scan, you may be feeling very worried. Try talking through your options with your doctor or midwife. You could also call the free helpline run by a charity called Antenatal Results and Choices.

You don't have to tell your employer for several more weeks, but as soon as you do, you will have maternity rights. You can attend antenatal appointments during paid work time.

You can also ask for a risk assessment of your work place. If you want to wait, the latest you can leave it is 15 weeks before the baby is due, which is around week 25.

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 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.

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 every day. Perhaps take a brisk walk in the park, or go for a swim. If you start any classes, make sure the instructor knows that you're pregnant. Don't overdo it though – listen to your body.

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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