Pregnancy is commonly dated from the first day of the last menstrual period, so the first counted weeks happen before conception. Use this guide to explore broad developmental milestones, approximate size references and changes some people notice.
Choose a trimester below, then read the week that interests you. Fruit comparisons and measurements are rounded references: they are not a scan, a prediction of your baby’s size, or a way to assess pregnancy health.
01
First trimester
Weeks 1–13
Early development begins after conception, while pregnancy weeks are counted from the last menstrual period. Appointments and screening schedules vary by country and individual history.
Week 1
Pregnancy dating starts before an embryo forms
Approx. lengthToo early for a useful size estimate
Approx. weightToo early for a useful size estimate
What may be developing
Gestational age is counted from the last menstrual period; there is no embryo yet.
What you may notice
A menstrual period may be happening; pregnancy symptoms are not expected yet.
A gentle thought
Use the first day of your period as a date reference; cycle lengths vary.
Week 2
Ovulation may happen around this time
Approx. lengthToo early for a useful size estimate
Approx. weightToo early for a useful size estimate
What may be developing
The body may be preparing for ovulation. Pregnancy timing varies from one cycle to another.
What you may notice
Some people notice mid-cycle changes, while others notice nothing.
A gentle thought
If you are tracking cycles, note dates without assuming ovulation happens on a fixed day.
Week 3
A microscopic cluster of cells
Approx. lengthToo early for a useful size estimate
Approx. weightToo early for a useful size estimate
What may be developing
Fertilisation may occur and the early cells begin dividing; implantation may happen later.
What you may notice
There may be no noticeable symptoms; early changes vary widely.
A gentle thought
Symptoms alone cannot confirm pregnancy; follow test instructions and seek care when needed.
Week 4
Poppy seed
Approx. length0.2 cm · 0.1 in
Approx. weightToo early for a useful size estimate
What may be developing
The early embryo implants and the structures that will support the placenta begin developing.
What you may notice
A missed period, breast tenderness or tiredness may occur, but symptoms can be absent.
A gentle thought
If a test is positive, arrange prenatal care and ask about suitable supplements.
Week 5
Sesame seed
Approx. length0.2 cm · 0.1 in
Approx. weightToo early for a useful size estimate
What may be developing
The brain, spinal cord and early blood vessels are forming; the heart is beginning to develop.
What you may notice
Nausea, tiredness, breast tenderness or sensitivity to smells may begin.
A gentle thought
Small, regular meals and fluids may help with mild nausea; ask a clinician about severe symptoms.
Week 6
Pea
Approx. length0.6 cm · 0.2 in
Approx. weightToo early for a useful size estimate
What may be developing
Small limb buds and early facial features begin to appear as the heart continues developing.
What you may notice
Nausea, frequent urination and tiredness are common, but not universal.
A gentle thought
If vomiting prevents you from keeping fluids down, contact your care team.
Week 7
Grape
Approx. length1 cm · 0.4 in
Approx. weightToo early for a useful size estimate
What may be developing
The brain grows rapidly while the eyelids and early structures of the arms and legs develop.
What you may notice
Nausea, breast changes and mood changes may continue.
A gentle thought
Rest when needed and check with your clinician before using medicines.
Week 8
Raspberry
Approx. length1.6 cm · 0.6 in
Approx. weight1 g · 0 oz
What may be developing
The embryo develops early fingers and toes; around this stage it is described as a fetus.
What you may notice
Bloating, nausea and tiredness may persist as the first trimester continues.
A gentle thought
Keep prenatal appointments and ask your care team about vitamins or medicines.
Week 9
Strawberry
Approx. length2.2 cm · 0.9 in
Approx. weight2 g · 0.1 oz
What may be developing
Facial features become clearer and the major internal organs continue developing.
What you may notice
Nausea or food aversions may continue; some people notice changing symptoms.
A gentle thought
Choose foods and activities that feel manageable, and discuss persistent symptoms with your clinician.
Week 10
Small apricot
Approx. length3 cm · 1.2 in
Approx. weight4 g · 0.1 oz
What may be developing
Small movements may be visible on a scan, although they are usually not felt yet.
What you may notice
Nausea, constipation or bloating may occur; symptoms differ from person to person.
A gentle thought
It is usually too early to feel movement; ask your clinician about any concern.
Week 11
Fig
Approx. length4.1 cm · 1.6 in
Approx. weight7 g · 0.2 oz
What may be developing
The fingers and toes separate further, and tiny nails and ears continue to form.
What you may notice
Some early symptoms may ease, while fatigue or breast tenderness can remain.
A gentle thought
Gentle activity may be appropriate for many pregnancies; confirm what is right for you.
Week 12
Lime
Approx. length5.4 cm · 2.1 in
Approx. weight14 g · 0.5 oz
What may be developing
Muscles and organs continue growing; the skeleton begins changing from cartilage toward bone.
What you may notice
Nausea may ease for some; appetite, heartburn or headaches may change.
A gentle thought
Write down questions for your next appointment, including screening options.
Week 13
Peach
Approx. length7.4 cm · 2.9 in
Approx. weight23 g · 0.8 oz
What may be developing
Movement becomes more coordinated and the reproductive organs continue developing.
What you may notice
Energy may improve; mild stretching sensations can happen as the uterus grows.
A gentle thought
Discuss screening and prenatal care choices with your maternity team.
02
Second trimester
Weeks 14–27
Growth and movement continue, and some people begin to feel movement during this trimester. Timing differs; ask your maternity team about screening and symptoms.
Week 14
Kiwi
Approx. length8.5 cm · 3.3 in
Approx. weight43 g · 1.5 oz
What may be developing
The head becomes more proportionate and the kidneys begin contributing to amniotic fluid.
What you may notice
A growing bump, nasal congestion or breast changes may be noticeable.
A gentle thought
Take breaks and change position for comfort; ask about pain that worries you.
Week 15
Apple
Approx. length10.1 cm · 4 in
Approx. weight70 g · 2.5 oz
What may be developing
Soft body hair begins to appear, and hearing development is underway.
What you may notice
Some people feel more energetic; mild backache or constipation may occur.
A gentle thought
Stay hydrated and ask your clinician about persistent headaches or discomfort.
Week 16
Avocado
Approx. length11.6 cm · 4.6 in
Approx. weight100 g · 3.5 oz
What may be developing
The nervous system supports more arm and leg movement; bones continue to develop.
What you may notice
The abdomen may grow and occasional pulling sensations can occur.
A gentle thought
Choose comfortable movement and rest; discuss new or worsening pain with your care team.
Week 17
Pomegranate
Approx. length12 cm · 4.7 in
Approx. weight140 g · 4.9 oz
What may be developing
Fingerprints and nails are developing, and the baby can make small movements.
What you may notice
Sleep changes, backache or occasional leg cramps may occur.
A gentle thought
Allow time for rest and ask your care team about any symptom that feels unusual.
Week 18
Bell pepper
Approx. length14.2 cm · 5.6 in
Approx. weight190 g · 6.7 oz
What may be developing
Hearing, swallowing and sucking reflexes continue to develop.
What you may notice
Some may notice early flutters; heartburn or constipation can also occur.
A gentle thought
If you notice movement, learn your baby’s usual pattern and report a change promptly.
Week 19
Beef tomato
Approx. length15.3 cm · 6 in
Approx. weight240 g · 8.5 oz
What may be developing
Early tooth buds are forming while the baby continues to gain weight.
What you may notice
Backache, heartburn or leg cramps may occur as the bump grows.
A gentle thought
Ask your care team about screening results and ways to manage discomfort safely.
Week 20
Banana
Approx. length25.6 cm · 10.1 in
Approx. weight300 g · 10.6 oz
What may be developing
A protective coating called vernix begins covering the skin; movement continues to develop.
What you may notice
Movement may be felt, but timing varies; backache or heartburn may continue.
A gentle thought
Follow your clinician’s advice about fetal movement; patterns differ between babies.
Week 21
Carrot
Approx. length26.7 cm · 10.5 in
Approx. weight360 g · 12.7 oz
What may be developing
Fine lanugo hair helps cover the skin as the placenta continues supporting growth.
What you may notice
Leg cramps, swelling or heartburn may occur; symptoms vary.
A gentle thought
Keep track of your baby’s usual movement and contact your maternity team if it changes.
Week 22
Sweet potato
Approx. length27.8 cm · 10.9 in
Approx. weight430 g · 15.2 oz
What may be developing
The lungs develop and the baby practises swallowing amniotic fluid.
What you may notice
Backache, indigestion or mild swelling may occur.
A gentle thought
A comfortable position and gentle stretching may help; seek advice for persistent pain.
Week 23
Large mango
Approx. length28.9 cm · 11.4 in
Approx. weight500 g · 17.6 oz
What may be developing
The limbs are becoming more proportionate and movement may become easier to notice.
What you may notice
Movement may feel more noticeable; sleep and back comfort can change.
A gentle thought
Notice your baby’s usual movement pattern and report a reduction or change promptly.
Week 24
Corn on the cob
Approx. length30 cm · 11.8 in
Approx. weight600 g · 21.2 oz
What may be developing
The brain and lungs continue maturing; development and outcomes vary between pregnancies.
What you may notice
Heartburn, backache or leg cramps may continue.
A gentle thought
Ask your maternity team which symptoms need urgent assessment in your pregnancy.
Week 25
Zucchini
Approx. length34.6 cm · 13.6 in
Approx. weight660 g · 23.3 oz
What may be developing
The baby continues gaining fat and may react to sounds with movement.
What you may notice
More noticeable movement, indigestion or tiredness may occur.
A gentle thought
Take breaks and choose comfortable positions; ask about symptoms that concern you.
Week 26
Cucumber
Approx. length35.6 cm · 14 in
Approx. weight760 g · 26.8 oz
What may be developing
The eyelids may begin opening and the eyes can respond to light.
What you may notice
Backache, heartburn or swelling may become more noticeable.
A gentle thought
Follow your care team’s guidance about movement and contact them if the pattern changes.
Week 27
Cauliflower
Approx. length36.6 cm · 14.4 in
Approx. weight875 g · 30.9 oz
What may be developing
The lungs and other organs continue maturing while the baby gains weight.
What you may notice
Sleep changes, backache or leg cramps may continue.
A gentle thought
Plan upcoming appointments and discuss any new swelling, headache or visual changes promptly.
03
Third trimester
Weeks 28–40
The baby continues to mature and gain weight. Keep scheduled care and contact your maternity team promptly if your baby’s usual movement pattern changes.
Week 28
Eggplant
Approx. length37.6 cm · 14.8 in
Approx. weight1,000 g · 35.3 oz
What may be developing
The third trimester begins; the brain, lungs and other organs keep maturing.
What you may notice
Heartburn, back strain or mild swelling may increase.
A gentle thought
Rest when possible and ask your care team about persistent heartburn or back pain.
Week 29
Butternut squash
Approx. length38.6 cm · 15.2 in
Approx. weight1,150 g · 40.6 oz
What may be developing
The baby continues adding fat and the organs keep preparing for life after birth.
What you may notice
Tiredness, indigestion or occasional practice contractions may occur.
A gentle thought
Keep your maternity team’s contact details available and ask about symptoms that concern you.
Week 30
Cabbage
Approx. length39.9 cm · 15.7 in
Approx. weight1,300 g · 45.9 oz
What may be developing
The eyes can focus more and the brain continues processing sensory information.
What you may notice
Sleep may be harder; heartburn, backache or swelling can occur.
A gentle thought
Try comfortable rest positions and mention breathing or sleep concerns at your appointment.
Week 31
Coconut
Approx. length41.1 cm · 16.2 in
Approx. weight1,500 g · 52.9 oz
What may be developing
The baby moves, sucks fingers and may begin recognising familiar voices.
What you may notice
Shortness of breath with activity, heartburn or fatigue may occur.
A gentle thought
Keep noting your baby’s usual movement; contact your maternity team if it changes.
Week 32
Bunch of celery
Approx. length42.4 cm · 16.7 in
Approx. weight1,700 g · 60 oz
What may be developing
Weight gain continues as the lungs and brain keep developing.
What you may notice
Sleep changes, backache or leg cramps may continue.
A gentle thought
Ask your care team about birth preferences and what to expect in the coming weeks.
Week 33
Pineapple
Approx. length43.7 cm · 17.2 in
Approx. weight1,900 g · 67 oz
What may be developing
The nervous system and brain continue developing; the skull remains flexible for birth.
What you may notice
Pelvic pressure, tiredness or practice contractions may occur.
A gentle thought
Discuss birth planning and any concerns about the baby’s position with your clinician.
Week 34
Cantaloupe melon
Approx. length45 cm · 17.7 in
Approx. weight2,150 g · 75.8 oz
What may be developing
The baby continues gaining fat and practising movements; position can still vary.
What you may notice
The baby may feel lower; pelvic pressure or frequent urination may occur.
A gentle thought
Keep your care team’s contact details close and ask when to call about labour signs.
Week 35
Honeydew melon
Approx. length46.2 cm · 18.2 in
Approx. weight2,400 g · 84.7 oz
What may be developing
Fat stores increase and movement should continue in the baby’s usual pattern.
What you may notice
Braxton Hicks contractions, backache or sleep changes may occur.
A gentle thought
Movement should remain in the usual pattern; contact your maternity unit for a change.
Week 36
Romaine lettuce
Approx. length47.4 cm · 18.7 in
Approx. weight2,600 g · 91.7 oz
What may be developing
The lungs are nearing maturity and sucking and feeding reflexes continue developing.
What you may notice
Pelvic pressure, tiredness or frequent urination may continue.
A gentle thought
Prepare practical birth essentials and ask your clinician about any new symptoms.
Week 37
Leek
Approx. length48.6 cm · 19.1 in
Approx. weight2,850 g · 100.5 oz
What may be developing
The baby continues practising movements and facial expressions as birth approaches.
What you may notice
The baby may settle lower; practice contractions can become more noticeable.
A gentle thought
Keep following your baby’s normal movement pattern and seek advice if it changes.
Week 38
Rhubarb stalk
Approx. length49.8 cm · 19.6 in
Approx. weight3,100 g · 109.3 oz
What may be developing
Most lanugo hair has reduced and the baby continues preparing for birth.
What you may notice
Sleep may be difficult and pelvic pressure or backache may continue.
A gentle thought
Review your birth plan and contact your care team about labour or wellbeing concerns.
Week 39
Watermelon
Approx. length50.7 cm · 20 in
Approx. weight3,300 g · 116.4 oz
What may be developing
The skin and protective vernix continue changing as the baby stores energy for birth.
What you may notice
Late-pregnancy discomforts may continue; labour signs vary.
A gentle thought
Do not wait if movement changes; call your maternity unit for advice.
Week 40
Watermelon
Approx. length51.2 cm · 20.2 in
Approx. weight3,400 g · 119.9 oz
What may be developing
Growth continues and the baby should keep moving in their usual pattern.
What you may notice
Braxton Hicks, backache and tiredness may occur as the due date approaches.
A gentle thought
At or after the due date, follow your care team’s plan for check-ins and contact them with concerns.
Pregnancy week-by-week questions
How are pregnancy weeks counted?
Gestational age is commonly counted from the first day of the last menstrual period, which is usually before conception. Your care team may adjust dating after reviewing your history or ultrasound.
Are the measurements normal ranges for my baby?
No. The rounded length and weight values are general references, not clinical centiles or a measurement of an individual baby. Your care team interprets scans using the full clinical context.
Do symptoms need to match the guide?
No. Symptoms vary, and having or not having a symptom cannot establish whether a pregnancy is healthy. Ask your care team about new or concerning symptoms.
When should I contact my maternity team?
Contact them promptly for concerns, and immediately for a reduction or change in your baby’s usual movement pattern. Follow local emergency guidance for severe symptoms.
Sources for further reading
Last updated November 3, 2026. Length references are adapted from NHS guidance; rounded weight references can vary across publications, and fruit comparisons are illustrative. None of these values measures an individual baby. The links below are general references, not a substitute for your care team’s assessment.