Pregnancy calendar
Week by week from your last period to the due date and beyond. Weeks are counted the way your doctor counts them: "week 20" means you are 20 weeks pregnant. Not sure which week you are in? Use the calculator.
First trimester
Weeks 1–13Week 1: your period
Before conception
Doctors count pregnancy from the first day of your last period, so week 1 is your period itself. Nothing is growing yet, but your body is already preparing an egg.
Week 2: ovulation
Before conception
In a typical 28-day cycle ovulation happens around day 14. The egg lives for about a day, while sperm can survive up to five days, so the days just before ovulation are the most fertile.
Week 3: fertilisation and the journey to the uterus
About the size of a grain of fine sand
The fertilised egg divides again and again as it travels down the fallopian tube. Around the end of this week it reaches the uterus and begins to burrow into the lining.
Week 4: a missed period and a positive test
About the size of a poppy seed
Implantation finishes and the embryo starts forming the structures that will support it: the amniotic sac, the yolk sac and the beginnings of the placenta. A home test can turn positive from about now.
Week 5: the heart begins
About the size of a sesame seed
The embryo now looks like a tiny tadpole. The groove that becomes the brain and spinal cord is closing, and a simple heart tube starts to contract by the end of the week.
Week 6: a heartbeat on the screen
About the size of a lentil
The embryo is curled like a comma. Its heart beats around 100 to 160 times a minute and can often be seen on an early scan. Facial features and limbs are starting to form.
Week 7: the brain grows fast
About the size of a blueberry · < 1 g
The head is large compared with the body because the brain is growing so quickly. Hands look like tiny paddles, and the kidneys, liver and lungs are starting to form.
Week 8: fingers, toes and the first appointment
About the size of a raspberry · 1 g
The embryo is making small, jerky movements that you cannot feel yet. Fingers and toes are forming, eyelids are growing, and the tail-like end has almost disappeared.
Week 9: from embryo to baby
About the size of a grape · 2 g
The embryonic period is ending. Every major organ has started to develop, and from now on the work is mostly growth and maturing. The eyes are formed but sealed shut.
Week 10: the fetal period begins
About the size of a kumquat · 4 g
Your baby is now officially a fetus. Bones are starting to harden, tiny nails are forming and the kidneys, intestines, brain and liver are functioning in a basic way.
Week 11: screening week opens
About the size of a fig · 7 g
The head makes up about half of your baby's length. Tooth buds, hair follicles and nail beds are forming, and the diaphragm is developing, which later brings hiccups. First-trimester screening starts this week.
Week 12: the dating scan
About the size of a lime · 14 g
Your baby can curl its toes, clench its fists and make sucking movements. The intestines move into the abdomen and the kidneys produce urine. Many parents share the news after this week's scan.
Week 13: fingerprints and the end of the first trimester
About the size of a pea pod · 23 g
Unique fingerprints are forming on tiny fingertips. The placenta is now complete and producing the hormones that sustain the pregnancy, which is one reason nausea fades for many women around now.
Second trimester
Weeks 14–27Week 14: welcome to the second trimester
About the size of a lemon · 43 g
Your baby can squint, frown and grimace, and is covered in fine hair called lanugo. The thyroid is working and the kidneys produce urine. Many women feel markedly better from now.
Week 15: sensing light
About the size of an apple · 70 g
Although the eyelids are still fused, your baby can sense light. The bones are hardening and would show on an X-ray. Hair and eyebrows are starting to grow.
Week 16: first flutters?
About the size of an avocado · 100 g
Your baby's eyes can make small side-to-side movements and the ears have reached their final position. Some women, especially in second pregnancies, feel the first faint flutters this week.
Week 17: building fat
About the size of a pear · 140 g
Your baby starts laying down fat, which will help with warmth and energy after birth. Sweat glands develop, the umbilical cord thickens and the heartbeat is now regulated by the brain.
Week 18: your baby can hear you
About the size of a bell pepper · 190 g
The bones of the inner ear have hardened enough for your baby to hear your heartbeat, your voice and the gurgle of your digestion. Nerves are being coated in protective myelin.
Week 19: a protective coating
About the size of a mango · 240 g
A white, waxy coating called vernix caseosa now protects your baby's skin from the amniotic fluid. The brain is developing specialised areas for smell, taste, hearing, vision and touch.
Week 20: halfway there
About the size of a banana · 300 g
You are at the midpoint. Your baby swallows regularly, produces meconium in the bowel and is starting to develop taste buds. The anatomy scan usually happens around now.
Week 21: coordinated kicks
About the size of a carrot · 360 g
Your baby's movements are becoming coordinated rather than random. Eyebrows and eyelids are complete, the bone marrow begins to make blood cells and the baby has sleep and wake cycles.
Week 22: a tiny newborn in miniature
About the size of a papaya · 430 g
Your baby now looks like a small newborn, with distinct lips, eyelids and eyebrows. The eyes are formed but the irises still lack colour. The sense of touch is developing fast and the baby explores by grasping.
Week 23: lungs in training
About the size of a grapefruit · 500 g
The lungs are developing the blood vessels and structures needed to breathe air, although they are far from ready. Your baby hears well now and may jump at a slammed door.
Week 24: the viability milestone
About the size of an ear of corn · 600 g
From this week a baby born early has a real chance of survival with intensive care. The lungs begin producing surfactant, the brain grows quickly and your baby can tell which way is up.
Week 25: filling out
About the size of a cauliflower · 660 g
Your baby is gaining fat and looking less wrinkled. Hair has colour and texture, the nostrils open and the startle reflex is in place. The baby responds to your voice with movement or a change in heart rate.
Week 26: eyes open
About the size of a head of lettuce · 760 g
Your baby's eyes, sealed since week 9, begin to open and blink. Brain wave activity for hearing and sight is detectable, lashes grow and the immune system is absorbing antibodies from you.
Week 27: the second trimester ends
About the size of a head of cauliflower · 875 g
Your baby sleeps and wakes on a schedule, opens and closes its eyes and sucks its fingers. The lungs could work with medical help if the baby were born now. Your voice is recognised.
Third trimester
Weeks 28–42Week 28: the third trimester
About the size of an aubergine (eggplant) · 1 kg
Your baby can blink, has eyelashes and dreams in REM sleep. Fat is layering up and the brain is forming its characteristic grooves. Appointments now become more frequent, and you will be asked about movements at each one.
Week 29: stronger every day
About the size of a butternut squash · 1.15 kg
Your baby's muscles and lungs are maturing and the head is growing to make room for the brain. Bones are fully developed but still soft, and they are absorbing a lot of calcium from you.
Week 30: a cabbage-sized baby
About the size of a cabbage · 1.3 kg
The fine lanugo hair is disappearing as fat takes over the job of keeping warm. The brain surface is forming its wrinkles, the eyes can focus and the bone marrow has taken over making red blood cells.
Week 31: all five senses
About the size of a coconut · 1.5 kg
All five senses work now. Your baby tracks light, processes sounds and signals from touch, and spends long stretches in REM sleep. There is less room, so big rolls give way to jabs and stretches, but movements should not become less frequent.
Week 32: practising for life outside
About the size of a jicama · 1.7 kg
Your baby practises breathing, sleeps most of the day and has nails that reach the fingertips. Many babies are now head-down, and most will be by 36 weeks. Know the signs of preterm labour from here.
Week 33: a flexible skull
About the size of a pineapple · 1.9 kg
The bones of the skull remain soft and unfused so the head can mould through the birth canal. The immune system is receiving antibodies, and your baby coordinates sucking, swallowing and breathing.
Week 34: nearly ready
About the size of a cantaloupe melon · 2.1 kg
Babies born from now usually do well with little help. The vernix coating thickens, fingernails reach the fingertips and your baby recognises songs and voices. Appointments cover feeding and birth plans.
Week 35: gaining weight fast
About the size of a honeydew melon · 2.4 kg
Most physical development is complete and your baby is putting on weight, around 200 to 250 g a week. The kidneys are fully developed and the liver can process waste. The head may begin to settle into your pelvis.
Week 36: dropping down
About the size of a romaine lettuce · 2.6 kg
Your baby is shedding lanugo and most of the vernix and may drop lower into your pelvis, which eases breathing but adds pressure. The digestive system is ready for milk and the lungs are nearly mature.
Week 37: early term
About the size of a bunch of Swiss chard · 2.9 kg
From 37 weeks and 0 days your baby is early term. Breathing, grasping and sucking are practised daily and the head is likely engaged. Lungs and brain still benefit from every extra day until 39 weeks.
Week 38: finishing touches
About the size of a leek · 3.1 kg
Your baby's organs are ready for life outside, while the brain and lungs continue fine-tuning. The grasp is firm, eye colour is set for now (often changing after birth) and the head is about the same circumference as the abdomen.
Week 39: full term
About the size of a mini watermelon · 3.3 kg
From 39 weeks and 0 days your baby is full term. The lungs are mature and new skin layers and fat help regulate temperature. Labour could start any day, and movements should stay strong until it does.
Week 40: your due date
About the size of a small pumpkin · 3.5 kg
This is the week of your due date, but most babies arrive within two weeks either side of it. Your baby is fully developed and still adding fat. The skull bones will overlap slightly during birth.
Week 41: late term
About the size of a watermelon · 3.6 kg
Your baby is late term and still growing. The placenta gradually works less efficiently after 41 to 42 weeks, so care providers monitor more closely and usually offer induction by 42 weeks.
Week 42: post-term
About the size of a watermelon · 3.7 kg
From 42 weeks and 0 days a pregnancy is post-term. The placenta may be less efficient and amniotic fluid decreases, so most guidelines recommend induction by this point with close monitoring if you choose to wait.
Get this week in Telegram
Our bot sends you a short weekly digest for your exact week, your due date countdown and a list of upcoming checkups. It also knows the warning signs that need a same-day call.
- ✓A short digest every new week
- ✓Countdown to your due date
- ✓Reminders about upcoming checkups
- ✓Kick counter and contraction timer