Week by week
Pregnancy week by week: your baby, from seed to pumpkin
How big your baby is each week, how they're growing and what's worth planning, from your first positive test to your due date. Not sure which week you're in? Use the due date calculator.
Updated November 2026
| Week | About the size of | Trimester |
|---|---|---|
| Week 4 | a poppy seed | First |
| Week 5 | a sesame seed | First |
| Week 6 | a lentil | First |
| Week 7 | a blueberry | First |
| Week 8 | a raspberry | First |
| Week 9 | a cherry | First |
| Week 10 | a strawberry | First |
| Week 11 | a lime | First |
| Week 12 | a plum | First |
| Week 13 | a lemon | First |
| Week 14 | a peach | Second |
| Week 15 | an apple | Second |
| Week 16 | an avocado | Second |
| Week 17 | a pear | Second |
| Week 18 | a bell pepper | Second |
| Week 19 | a mango | Second |
| Week 20 | a banana | Second |
| Week 21 | a carrot | Second |
| Week 22 | a sweet potato | Second |
| Week 23 | a grapefruit | Second |
| Week 24 | an ear of corn | Second |
| Week 25 | a cauliflower | Second |
| Week 26 | a head of lettuce | Second |
| Week 27 | a cabbage | Second |
| Week 28 | an eggplant | Third |
| Week 29 | a butternut squash | Third |
| Week 30 | a cucumber | Third |
| Week 31 | a coconut | Third |
| Week 32 | a jicama | Third |
| Week 33 | a pineapple | Third |
| Week 34 | a cantaloupe | Third |
| Week 35 | a honeydew melon | Third |
| Week 36 | a romaine lettuce | Third |
| Week 37 | a bunch of chard | Third |
| Week 38 | a leek | Third |
| Week 39 | a mini watermelon | Third |
| Week 40 | a small pumpkin | Third |
Weeks 1 to 4: before you know
Pregnancy is counted from the first day of your last period, so in weeks 1 and 2 you aren't pregnant yet. In a 28-day cycle you conceive at around 2 weeks, and the fertilised egg implants in the womb during week 3 or 4. A pregnancy test can usually pick up the hormone hCG from around the time your period is due.
Worth doing: take a folic acid supplement (400 micrograms a day until week 12, unless you're advised a higher dose) and contact your doctor or midwife to start your care.
Weeks 5 to 8: the heart starts beating
The neural tube, which becomes the brain and spinal cord, forms and closes. A heartbeat can often be seen on an early ultrasound from around 6 weeks. Arms and legs start as small buds. Many people now feel sick, tired and have tender breasts.
Worth doing: book your first appointment with your midwife or doctor (in the UK, ideally before 10 weeks). Ask about the screening tests on offer.
Weeks 9 to 12: all the main organs are in place
From around 10 weeks the embryo is called a fetus. The main organs have formed and now need to grow and mature. Fingers and toes separate. Nausea often starts to ease towards the end of the first trimester.
Worth doing: your first scan and screening usually happen between 10 and 14 weeks.
Weeks 13 to 16: into the second trimester
The second trimester starts at week 14. Your baby's skeleton is hardening from cartilage into bone, and they can make sucking and swallowing movements. Many people find they have more energy now.
Weeks 17 to 20: first movements
Many people feel their baby move for the first time between 16 and 24 weeks: often a fluttering at first, and later in a first pregnancy. At 20 weeks you're halfway.
Worth doing: the anomaly (anatomy) scan is usually offered between 18 and 21 weeks.
Weeks 21 to 24: a regular pattern
Your baby's movements become stronger and settle into a pattern. They can respond to sounds. From around 24 weeks, a baby born very early has a chance of survival with specialist neonatal care.
Weeks 25 to 28: into the third trimester
Your baby's eyes open and they keep putting on weight. The third trimester starts at week 28. You may be offered a gestational diabetes test between 24 and 28 weeks, and an anti-D injection if your blood group is rhesus negative.
Important: get to know your baby's usual pattern of movements. If they slow down, stop or change, contact your maternity unit straight away. Don't wait until the next day.
Weeks 29 to 32: growing and practising
Your baby's lungs and brain keep maturing and they're laying down fat. You may feel Braxton Hicks contractions: tightenings that come and go without getting stronger.
Worth doing: prenatal classes, and start your birth plan.
Weeks 33 to 36: getting into position
Most babies turn head-down by 36 weeks. If yours is bottom-first (breech) at 36 weeks, your care team may talk to you about turning the baby or how to give birth.
Worth doing: pack your hospital bag and make sure the car seat is fitted.
Weeks 37 to 40 and beyond: ready to meet you
From 37 weeks your baby is early term, and from 39 weeks full term. Labor can start any time. Call your maternity unit if your waters break, you have bleeding, your baby moves less or you're unsure about your contractions. If your baby hasn't arrived by around 41 weeks, you'll usually be offered a membrane sweep or an induction.
Questions parents ask
Why does pregnancy count from my last period?
Because the first day of your last period is usually the date you know, while the day you conceived usually isn't. It means you're counted as 2 weeks pregnant on the day you conceive, and a full-term pregnancy is about 40 weeks.
Are the fruit sizes exact?
No. They're a friendly way to picture your baby's length at each stage. Babies grow at their own pace, and your scans are what matter.
When do the trimesters start?
The first trimester runs to the end of week 13, the second from week 14 to the end of week 27, and the third from week 28 to birth.
Sources
Written from the guidance above. It's general information: your midwife, doctor or pediatrician knows your situation.
Amelia gives general information, not medical advice. Always follow your own midwife, doctor or care team, and call them whenever you're unsure.