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 21 – your second trimester

As you cruise into the second 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 could start feeling rather wobbly as your bump gets bigger. It's hardly surprising if you're clumsier than usual, as your centre of gravity has changed and your joints are looser. If you fall over, don't panic, as there's lots of cushioning in your belly to protect your baby. That's what the amniotic sac is for. However, for peace of mind, you should get checked out by your midwife or doctor if you do take a tumble. 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 raring to go just when you want to nod off. Have power naps when you can to make up for lost sleep at night. Read more sleep tips.

Dump the junk!

A healthy diet, with plenty of fresh fruit and veg, will give you more energy than junk food, and help you and your baby thrive. 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 that you might enjoy making (and eating!).

Simple swaps

Try these healthier and tastier alternatives…

Say no to takeaway pizza, but say yes to cheats' pizza calzone.

Say no to an Indian delivery, but say yes to chicken and banana korma (use tofu if you're veggie).

Say no to fish 'n' chips from your local chippy, but say yes to homemade good old fish 'n' chips.

There are a few foods to avoid during pregnancy. Steer clear of soft cheese with white rind, blue cheese, paté and undercooked meats.

Second trimester pregnancy symptoms (at 21 weeks)

Hopefully you're feeling good now. Don't ignore any painful symptoms and assume they'll go away. If you have a severe headache that lasts for more than 2 or 3 hours, and isn't helped by paracetamol, then call your midwife, GP surgery or NHS 111. It's very unlikely, but it could be a sign of a dangerous condition called pre-eclampsia. This affects some women in the second half of their pregnancy. However it's much more likely that you're not drinking enough water, so make sure that you stay hydrated and drink at least 8 medium glasses of fluid a day (for example, fruit juice, water, fruit teas and milk).

This week, your signs of pregnancy could include:

Tommy's has also produced a pregnancy guide with a further list of 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 five wholemeal 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 so it can 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 sprouting hair and eyebrows – some babies are born with very little hair, others have lots. It doesn't make as much difference, within the first year of their life, they'll probably lose all the hair they were born with as their hormone levels change.

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

Action stations

Pregnancy can be a happy time but, for some women, it's stressful and there are lots of difficult decisions to make. If you were given any unexpected news at your anomaly scan, then you may be feeling very worried. Maybe you've been offered further tests and aren't sure what to do. 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 and 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, then the latest you can leave it is 15 weeks before the baby is due, which is around week 25. It will probably be rather obvious by then anyway!

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.

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 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 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.

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.

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