Pregnancy Week by Week

Follow your journey from conception to birth with our detailed UK-focused guide to your baby's development and your body's changes.

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First Trimester

Weeks 1 to 12: The foundation of life is laid. From a single cell to a fully formed tiny person.

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Microscopic grain of sand

Illustration of a poppy seed, showing the approximate size of the baby at week 4

Your baby isabout the size of aPoppy seedApprox. 0.2cm

Illustration of a sesame seed, showing the approximate size of the baby at week 5

Your baby isabout the size of aSesame seedApprox. 0.2cm

Illustration of a lentil, showing the approximate size of the baby at week 6

Your baby isabout the size of aLentilApprox. 0.6cm

Illustration of a blueberry, showing the approximate size of the baby at week 7

Your baby isabout the size of aBlueberryApprox. 1cm

Illustration of a raspberry, showing the approximate size of the baby at week 8

Your baby isabout the size of aRaspberryApprox. 1.6cm

Illustration of a cherry, showing the approximate size of the baby at week 9

Your baby isabout the size of aCherryApprox. 2.2cm

Illustration of a strawberry, showing the approximate size of the baby at week 10

Your baby isabout the size of aStrawberryApprox. 3cm

Illustration of a lime, showing the approximate size of the baby at week 11

Your baby isabout the size of aLimeApprox. 4.1cm

Illustration of a plum, showing the approximate size of the baby at week 12

Your baby isabout the size of aPlumApprox. 5.4cm

Second Trimester

Weeks 13 to 26: The 'golden period'. Energy returns as your baby grows rapidly and you feel those first magical flutters.

Illustration of a lemon, showing the approximate size of the baby at week 13

Your baby isabout the size of aLemonApprox. 7.4cm

Illustration of a peach, showing the approximate size of the baby at week 14

Your baby isabout the size of aPeachApprox. 8.5cm

Illustration of a lemon, showing the approximate size of the baby at week 15

Your baby isabout the size of aLemonApprox. 10.1cm

Illustration of a avocado, showing the approximate size of the baby at week 16

Your baby isabout the size of aAvocadoApprox. 11.6cm

Illustration of a pear, showing the approximate size of the baby at week 17

Your baby isabout the size of aPearApprox. 12cm

Illustration of a bell pepper, showing the approximate size of the baby at week 18

Your baby isabout the size of aBell pepperApprox. 14.2cm

Illustration of a mango, showing the approximate size of the baby at week 19

Your baby isabout the size of aMangoApprox. 15.3cm

Illustration of a banana, showing the approximate size of the baby at week 20

Your baby isabout the size of aBananaApprox. 25.6cm

Illustration of a pomegranate, showing the approximate size of the baby at week 21

Your baby isabout the size of aPomegranateApprox. 26.7cm

Illustration of a papaya, showing the approximate size of the baby at week 22

Your baby isabout the size of aPapayaApprox. 27.8cm

Illustration of a grapefruit, showing the approximate size of the baby at week 23

Your baby isabout the size of aGrapefruitApprox. 28.9cm

Illustration of a ear of corn, showing the approximate size of the baby at week 24

Your baby isabout the size of aEar of cornApprox. 30cm

Illustration of a rutabaga, showing the approximate size of the baby at week 25

Your baby isabout the size of aRutabagaApprox. 34.6cm

Illustration of a spring onion, showing the approximate size of the baby at week 26

Your baby isabout the size of aSpring onionApprox. 35.6cm

Third Trimester

Weeks 27 to 42: The home stretch. Your baby is putting on weight and practicing for their big debut.

Illustration of a cauliflower, showing the approximate size of the baby at week 27

Your baby isabout the size of aCauliflowerApprox. 36.6cm

Illustration of a aubergine, showing the approximate size of the baby at week 28

Your baby isabout the size of aAubergineApprox. 37.6cm

Illustration of a butternut squash, showing the approximate size of the baby at week 29

Your baby isabout the size of aButternut squashApprox. 38.6cm

Illustration of a large cabbage, showing the approximate size of the baby at week 30

Your baby isabout the size of aLarge cabbageApprox. 39.9cm

Illustration of a coconut, showing the approximate size of the baby at week 31

Your baby isabout the size of aCoconutApprox. 41.1cm

Illustration of a squash, showing the approximate size of the baby at week 32

Your baby isabout the size of aSquashApprox. 42.4cm

Illustration of a pineapple, showing the approximate size of the baby at week 33

Your baby isabout the size of aPineappleApprox. 43.7cm

Illustration of a cantaloupe melon, showing the approximate size of the baby at week 34

Your baby isabout the size of aCantaloupe melonApprox. 45cm

Illustration of a honeydew melon, showing the approximate size of the baby at week 35

Your baby isabout the size of aHoneydew melonApprox. 46.2cm

Illustration of a head of romaine lettuce, showing the approximate size of the baby at week 36

Your baby isabout the size of aHead of romaine lettuceApprox. 47.4cm

Illustration of a bunch of swiss chard, showing the approximate size of the baby at week 37

Your baby isabout the size of aBunch of Swiss chardApprox. 48.6cm

Illustration of a leek, showing the approximate size of the baby at week 38

Your baby isabout the size of aLeekApprox. 49.8cm

Illustration of a small watermelon, showing the approximate size of the baby at week 39

Your baby isabout the size of aSmall watermelonApprox. 50.7cm

Illustration of a small pumpkin, showing the approximate size of the baby at week 40

Your baby isabout the size of aSmall pumpkinApprox. 51.2cm

Illustration of a large watermelon, showing the approximate size of the baby at week 41

Your baby isabout the size of aLarge watermelonApprox. 51cm

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