Tommy's PregnancyHub

21 weeks pregnant - all you need to know

Wow - you’re halfway there! Your baby is growing hair and starting to look much more like the baby you’ll meet at the end of your pregnancy.
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Your baby’s development this week

Your baby now measures around 17cm (7 inches) and weighs about 350g (12 oz).

Their facial features are now obvious, with a clearly defined nose and fully developed lips and tongue.

Your pregnancy symptoms in week 21

Your sex drive

Your sex drive will probably change during your pregnancy. Some people find that their sexual desire gets higher, for others it goes down. 

As a very general guide, most people find that their sexual desire goes down in the first trimester, goes up again in the second trimester and then goes down again in the third. But this will probably be different for everyone.

Sex will not hurt the baby. It’s safe to have sex when you’re pregnant unless your doctor or midwife has told you not to.

Find out more about sex in pregnancy.

Headaches in pregnancy

Mild headaches are common in pregnancy. They are often caused by hormones or dehydration. 

However, it’s important to look out for signs of pre-eclampsia from this stage of pregnancy. Contact your midwife or maternity unit straight away if you experience any of the following symptoms: 

  • a severe headache
  • vision problems, such as blurring or seeing flashing lights
  • pain just below your ribs
  • vomiting
  • a sudden increase in swelling of your face, hands, feet or ankles.

Find out more about pre-eclampsia.

Changes to your hair

Women shed a lot less hair during their pregnancy because of a change in hormones. So you may notice that your hair appears thicker or fuller. 

This excess hair may fall out after your baby is born. Postpartum hair loss is common and temporary. You should find that the hair grows back in time. Some research suggests the hair loss rarely continues beyond 15 months after having a baby.

What to do in week 21

Thinking about your birth options

There’s lots to think about when it comes to the birth. Where do I want to give birth? How? Who do I want to be there? 

Don’t worry, we’ve got all the information you need to make an informed decision about what’s best for you. Your midwife or doctor will also be there to help and advise you.

Are you expecting more than one baby? Find out about giving birth to multiple babies

What can I eat to boost my iron levels now I'm pregnant?

Anaemia is common in pregnancy. This is a blood condition that develops when you don’t have enough red blood cells. Red blood cells contain haemoglobin, a protein that carries oxygen around your body and to your baby. 

Most people should be able to get all the iron they need by eating a healthy, balanced diet. Eating well will help you either prevent anaemia or manage your symptoms if you have it. 

Try to eat iron-rich foods regularly, such as: 

  • wholegrains, such as brown rice
  • red meat (cooked thoroughly)
  • fresh green leafy vegetables, such as broccoli and spinach
  • iron-fortified foods, such as breakfast cereals.

Find out more about anaemia symptoms and treatments.

I am vegan or vegetarian. Is it safe during pregnancy?

As long as your diet is balanced and includes a range of foods from all food groups, then being vegan or vegetarian in pregnancy is perfectly safe. If you have any questions about your diet and pregnancy, talk to your doctor or midwife.

Try to make sure you get enough iron and vitamin B12, which are mainly found in meat and fish.

Find out more about vegetarian or vegan diets during pregnancy.

Enjoy bonding with your baby

You're halfway to meeting your baby! Your baby can hear your voice so try talking or singing to them. This will help them get to know your voice, helping them to feel safe and secure. If you have a partner, they can join in with this too. 

1. Regan, Lesley (2019) Your pregnancy week by week, Penguin Random House, London

2. Polomeno V (2000) Sex and pregnancy: a perinatal educator’s guide. The Journal of Perinatal Education. 2000 Fall; 9(4): 15–27.doi: 10.1624/105812400X87879

3. NHS. Sex in pregnancy. https://www.nhs.uk/pregnancy/keeping-well/sex/ (Page last reviewed: 16 March 2021 Next review due: 16 March 2024)

4. NHS. Headaches in pregnancy. https://www.nhs.uk/pregnancy/related-conditions/common-symptoms/headaches/ (Page last reviewed: 8 April 2021 Next review due: 8 April 2024)

5. Piérard-Franchimont, C., & Piérard, G. E. (2013). Alterations in hair follicle dynamics in women. BioMed research international, 2013, 957432. https://doi.org/10.1155/2013/957432

6. The Association of UK Dietitians [email protected] Iron food factsheet https://www.bda.uk.com/resource/iron-rich-foods-iron-deficiency.html (Page last reviewed: April 2021 Next review due: April 2024)

7. NHS. Vegetarian or vegan and pregnant. https://www.nhs.uk/pregnancy/keeping-well/vegetarian-or-vegan-and-pregnant/ (Page last reviewed: 8 August 2018 Next review due: 8 August 2021)

8. NHS Inform. Attachment and bonding during pregnancy. (June 2021) https://www.nhsinform.scot/ready-steady-baby/pregnancy/relationships-and-wellbeing-in-pregnancy/attachment-and-bonding-during-pregnancy

Review dates

Last reviewed: May 2022
Last review: May 2025