Pregnancy week by week, weeks 1 to 40
What your baby is doing, how your body may feel, and the self-care that matters most — written in plain language and aligned with WHO antenatal care recommendations and NICE guidance. Educational only; it never replaces advice from your own midwife or doctor.
First trimester · Weeks 1–13
Trimester 1 · Baby is about not yet conceived — this week is counted from your last period
Pregnancy is dated from the first day of your last period, so conception has not happened yet. Your body is shedding the uterine lining and preparing a fresh one.
Week 2Trimester 1 · Baby is about a single egg, smaller than a grain of sand
An egg is maturing and your body is preparing to release it. Fertilisation usually happens at the end of this week.
Week 3Trimester 1 · Baby is about a cluster of cells, about the size of a pinhead
The fertilised egg divides as it travels down the fallopian tube towards the uterus.
Week 4Trimester 1 · Baby is about a poppy seed
The embryo settles into the uterine lining and the placenta starts to form.
Week 5Trimester 1 · Baby is about a sesame seed
The neural tube — which becomes the brain and spine — is forming, and a tiny heart begins to beat.
Week 6Trimester 1 · Baby is about a lentil
Facial features, arm and leg buds begin to appear. The heartbeat can often be seen on an early scan.
Week 7Trimester 1 · Baby is about a blueberry
The brain is growing quickly and tiny hands and feet are starting to form.
Week 8Trimester 1 · Baby is about a raspberry
The baby is now moving, though far too small for you to feel it. Fingers and toes are separating.
Week 9Trimester 1 · Baby is about a grape
The heart has four chambers and essential organs continue developing.
Week 10Trimester 1 · Baby is about a strawberry
The baby is now called a fetus. Vital organs are formed and will grow from here.
Week 11Trimester 1 · Baby is about a fig
Bones are hardening and the baby can hiccup, though you cannot feel it yet.
Week 12Trimester 1 · Baby is about a lime
Reflexes are developing, fingers and toes are fully separated and the face looks more human.
Week 13Trimester 1 · Baby is about a pea pod
Vocal cords form and the baby starts producing urine into the amniotic fluid.
Second trimester · Weeks 14–27
Trimester 2 · Baby is about a lemon
The baby can squint, frown and suck a thumb. Fine hair called lanugo begins to grow.
Week 15Trimester 2 · Baby is about an apple
The baby can sense light through the closed eyelids and is moving freely.
Week 16Trimester 2 · Baby is about an avocado
Facial muscles work, the baby can hear muffled sounds, and growth is rapid.
Week 17Trimester 2 · Baby is about a pear
Fat begins to form under the skin and the skeleton hardens from cartilage to bone.
Week 18Trimester 2 · Baby is about a sweet potato
The baby yawns, stretches and hears your heartbeat and voice.
Week 19Trimester 2 · Baby is about a mango
A protective coating called vernix covers the skin, and the senses are developing quickly.
Week 20Trimester 2 · Baby is about a banana
Halfway there. The baby swallows amniotic fluid and produces first stool, called meconium.
Week 21Trimester 2 · Baby is about a carrot
Movements become stronger and a sleep–wake rhythm begins to form.
Week 22Trimester 2 · Baby is about a papaya
Eyebrows and lips are visible and the baby responds to sound and touch.
Week 23Trimester 2 · Baby is about a large mango
Lungs are developing surfactant, and hearing is sharp enough to recognise your voice.
Week 24Trimester 2 · Baby is about an ear of corn
The baby reaches an important stage of lung and brain development.
Week 25Trimester 2 · Baby is about a cauliflower
The baby's hands can grip and the sense of balance is developing.
Week 26Trimester 2 · Baby is about a lettuce
Eyes begin to open and the baby responds to bright light.
Week 27Trimester 2 · Baby is about a head of broccoli
Regular sleep cycles form and the baby may hiccup — small rhythmic jumps you can feel.
Third trimester · Weeks 28–40
Trimester 3 · Baby is about an aubergine
The baby's brain grows rapidly and eyes can blink.
Week 29Trimester 3 · Baby is about a butternut squash
Muscles and lungs continue maturing and the baby gains weight steadily.
Week 30Trimester 3 · Baby is about a large cabbage
The baby can distinguish light and dark and practises breathing movements.
Week 31Trimester 3 · Baby is about a coconut
All five senses are working and the baby responds to your movement and voice.
Week 32Trimester 3 · Baby is about a squash
Most babies move head-down around now, preparing for birth.
Week 33Trimester 3 · Baby is about a pineapple
The immune system strengthens as antibodies pass from you to the baby.
Week 34Trimester 3 · Baby is about a melon
Fingernails reach the fingertips and fat continues building under the skin.
Week 35Trimester 3 · Baby is about a honeydew melon
Lungs are nearly mature and the baby practises breathing rhythmically.
Week 36Trimester 3 · Baby is about a romaine lettuce head
The baby is gaining around 30 grams a day and settling into a birth position.
Week 37Trimester 3 · Baby is about a swiss chard bunch
The baby is early term. Organs are ready, although the brain keeps developing.
Week 38Trimester 3 · Baby is about a leek
The baby continues gaining fat and shedding the fine body hair.
Week 39Trimester 3 · Baby is about a small watermelon
The baby is full term with fully developed lungs, ready to breathe air.
Week 40Trimester 3 · Baby is about a pumpkin
Your baby is fully grown and ready to be born. Many babies arrive in the week or two after 40 weeks.