17 weeks pregnant: baby's development, your baby bump and vitamin D

Your baby is about the size of an orange, about 12cm long, and weighs roughly 150g. Your bump is getting bigger.

Your baby’s development this week 

By the start of the 17th week, your baby’s size has increased dramatically to about 13cm long and weighs about 150g (5oz).

If you could see your baby’s face, you’d notice eyelashes and eyebrows starting to grow. And if you could take their hand, you’d see they already have a unique fingerprint.

Although your baby’s head is still a little big, their body, arms and legs are growing fast and becoming more proportional. 

Your baby’s eyes can move, although their eyelids are still shut, and will stay closed for most of the second trimester.

Your pregnancy symptoms in week 17

Do you have swollen feet? Suffering from pelvic pain or headaches?

Here’s our guide to 10 common pregnancy complaints (and how to avoid them).

Your baby bump

Your waist will become a little thicker as your womb moves up out of your pelvis and your bump becomes more noticeable. If you've been pregnant before, your bump may start showing a bit sooner than for first-time mums. This is because muscles in your womb and stomach may be stretched from your previous pregnancy. 

Your baby’s movements

You may feel your baby move as early as 16 weeks of pregnancy, but most women usually feel something between 18 and 24 weeks. Feeling your baby move is a sign that they are well

Pregnancy worries and stress

You may have expected to feel excited and happy throughout your pregnancy, but no one can feel positive all the time. Feeling low, stressed or anxious is common in pregnancy. It doesn’t mean it was a mistake to get pregnant or that you won’t love your baby.

Talk to your midwife about how you feel. They are there to talk about your mental wellbeing in pregnancy, as well as your physical health. Our free mental wellbeing download can also help you think about how you are feeling during your pregnancy and plan for after the birth. You can complete your pregnancy and post-birth wellbeing plan at any point during pregnancy.

Top tips for looking after your wellbeing.

What to do in week 17

You’ll have your second scan, known as the fetal anomaly scan between 18 and 21 weeks. This is to check your baby’s growth and development.

Most scans show that the baby is developing normally because most babies are healthy. But if you have any symptoms that worry you, or you just feel that something is wrong, don’t rely on the results of a recent scan or wait until your next one. Contact your midwife or local maternity unit.

You may be able to find out the sex of your baby at this scan. Some hospitals have a policy not to reveal this. Tell your sonographer at the start of your scan if you want to know your baby’s sex. 

It isn’t possible for the sonographer to be 100% certain about your baby’s sex. Find out more about pregnancy ultrasound scans.

“I didn’t find out what we were expecting in my first pregnancy. In some ways waiting was excruciating but it was so exciting not knowing. We found out with our second, but I think I preferred the element of surprise the first time!”

Anterior placenta

Some people find out that they have an anterior placenta during their second ultrasound scan. This is when the placenta attaches to the front of the uterus. It is very unlikely that this will cause complications, but it may make it a bit harder to feel your baby move because your baby is cushioned by the placenta lying at the front of your stomach.

Find out more about an anterior placenta.

Premature labour and birth

Some people will be told they are at risk of giving birth early. In these cases, they will have more care or treatment to try and reduce the chances of this happening. 

You do not need to eat for two

You may be wondering what to eat, or how much. No matter what well-meaning people might say, you don’t need to eat for two during pregnancy. Your baby takes everything they need from your body, and will grow well without you taking in any extra calories at all until the last three months.

Once you reach 6 months pregnancy, you may need an extra 200 calories a day, which is around half a sandwich.

Here are 10 super snack suggestions to help your baby grow.

Are you getting enough vitamin D?

All pregnant women should take a 10 microgram supplement of vitamin D each day. This will help reduce the risk of your baby having soft bones, which can lead to rickets (a disease that affects bone development in children).

Find out about more vital supplements in pregnancy.

Exercise and pregnancy

Exercise isn’t dangerous for your baby, so keep up your normal physical activity for as long as you feel comfortable.

But remember not to exhaust yourself.

If you weren’t physically active before you got pregnant, don’t start doing strenuous exercise. Gentle exercise such as walking or swimming will help. If you do any exercise classes, tell the instructor you are pregnant.

Find out more about when to be careful when exercising in pregnancy

“I exercised throughout both my pregnancies, right up until my due date. I was more tired in the second pregnancy, because I was running around after my daughter, but I always did something active because it made me feel better.”

Pelvic floor exercises

The pelvic floor muscles come under great strain in pregnancy and childbirth. If these muscles weaken you may find that you leak urine when you cough or sneeze. Pelvic floor exercises can lower your chances of experiencing incontinence after having your baby – and it’s never too early to start. 

Free prescriptions and NHS dental care

Talk to your GP or midwife if you haven't applied for your maternity exemption certificate yet. This entitles you to get free NHS dental treatment and free prescriptions.

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

2. Royal College of Obstetricians and Gynaecologists (2019) Your baby's movements in pregnancy: information for you, London RCOG https://www.rcog.org.uk/globalassets/documents/patients/patient-information-leaflets/pregnancy/pi-your-babys-movements-in-pregnancy.pdf

3. The Royal College of Obstetricians & Gynaecologists (February 2017) Maternal Mental Health – Women’s Voices https://www.rcog.org.uk/globalassets/documents/patients/information/maternalmental-healthwomens-voices.pdf

4. NHS. Ultrasound scans in pregnancy. https://www.nhs.uk/pregnancy/your-pregnancy-care/ultrasound-scans/ (Page last reviewed: 9 December 2020. Next review due: 9 December 2023) Accessed: September 2021

5. Clinical Knowledge Summaries (2021) Antenatal care – uncomplicated pregnancy https://cks.nice.org.uk/antenatal-care-uncomplicated-pregnancy#!topicSummary

6. NICE Guidelines (2010) Weight management before, during and after pregnancy National Institute for Health and Care Excellence https://www.nice.org.uk/guidance/ph27

7. NHS. Prevention-Rickets and osteomalacia. https://www.nhs.uk/conditions/rickets-and-osteomalacia/prevention/ (Page last reviewed: 5 August 2021 Next review due: 5 August 2024)

8. NHS. Exercise in pregnancy. https://www.nhs.uk/pregnancy/keeping-well/exercise/ (Page last reviewed: 20 January 2020 Next review due: 20 January 2023)

9. NHS. What are pelvic floor exercises? https://www.nhs.uk/common-health-questions/womens-health/what-are-pelvic-floor-exercises/ (Page last reviewed: 14 April 2020 Next review due: 14 April 2023)

Review dates
Reviewed: 11 July 2022
Next review: 11 July 2025