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17 weeks pregnant

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Even though you may only feel light flutters within your belly, your baby is becoming active and moving around more1. By the time you’re 17 weeks pregnant, their major internal systems are becoming established. Vitamin D still forms a crucial part of your pregnancy diet to support your baby’s bone development.

Major developments and increased movement at 17 weeks

Now weighing roughly 150g (just over 5oz)1 and measuring around 13cm from crown to rump2, your baby’s body is growing bigger and becoming more in proportion with their head1

 "Your baby’s development at 17 weeks"

Their hair, eyebrows and eyelashes are growing longer3, and they can also open and close their mouth and move their eyes, which are still shut1. Although your baby is also putting on a bit of weight, they still don’t have much fat but their special fat-storing ‘adipose tissue’ is beginning to form4.

“…they can also open and close their mouth and move their eyes...”

Internally, your baby’s major body systems are becoming established. By the 17th week of pregnancy, their heart may be beating around 140–150 bpm2 – much faster than the average resting adult, whose bpm ranges from 60–1005. Their respiratory system is developing too, and their chest will rise and fall as they start practising how to breathe3.

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The future benefits of vitamin D for your baby

Vitamin D forms an important part of a healthy pregnancy diet. It regulates the levels of calcium and phosphate in your body and supports the growth and development of your baby’s bones6. Vitamin D is especially important for normal bone development, as a deficiency can cause your baby’s bones to soften, which can lead to rickets, in extreme cases7. Furthermore, the vitamin D you consume during your pregnancy will also help build up your baby’s personal store, which they will rely on in the first few months of life7.

“It’s recommended that you get 10 micrograms of vitamin D each day during pregnancy.”

The most efficient way to get vitamin D is through exposure to the UVB rays in sunlight. However, in the UK we only get around 6 months of effective sunlight each year during the summer. This means that getting enough vitamin D through skin exposure to sun alone may not be enough to support your baby during pregnancy.

You can increase your vitamin D intake by making sure you eat certain foods, but the best way to make sure you’re getting enough is to take it as a supplement. It’s recommended that you get 10 micrograms of vitamin D each day during pregnancy8.

Next Steps

Make sure your pregnancy supplement includes vitamin D and if not, buy a separate one.

You can also add some of the following vitamin D-rich foods to your shopping list9:

  • Oily fish, including herring, mackerel, sardines, salmon or trout: it’s recommended that you limit your intake to two portions per week due to the toxins they may contain
  • Eggs – the yolk contains the vitamin D
  • Fortified foods – some brands of milk, margarines, low-fat spreads and some breakfast cereals have added vitamin D

View references

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1. NHS UK. You and your baby at 17-20 weeks pregnant [Online]. 2013. Available at: [Accessed July 2014]

2. Murkoff H, Mazel S. What to Expect When You’re Expecting. 4th ed. London: Simon & Schuster Ltd, 2009.

3. Deans A. Your New Pregnancy Bible, The experts’ guide to pregnancy and early parenthood. 4th ed. London: Carroll & Brown Publishers Limited, 2013.

4. Curtis GB, Schuler J. Your pregnancy week by week. 7th ed. Cambridge: Fisher books, 2011.

5. NHS UK. How do I check my pulse? [Online]. 2013. Available at: [Accessed July 2014]

6. European Union. Commission Regulation (EC) No 983/2009 of 21 October 2009 on the authorisation and refusal of authorisation of certain health claims made on food and referring to the reduction of disease risk and to children’s development and health. OJ L 277 2009. 3-12.

7. NHS UK. Vitamins and nutrition in pregnancy [Online]. 2013. Available at: [Accessed April 2014]

8. Department of Health. Report on Health and Social Subjects 41. Dietary Reference Values for Food Energy and Nutrients for the United Kingdom. London: TSO, 1991.

9. Gandy J (ed). Manual of Dietetic Practice. 5th ed. Oxford: Wiley Blackwell, 2014. p. 922.

Last reviewed: 14th July 2016

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