Your pregnancy, week by week
Pregnancy Week by Week
What's happening in there this week? Every week from 4 to 42: how your baby is developing, their approximate size, what you may be feeling, and the care milestone to have on the calendar — aligned to ACOG's prenatal schedule. Enter your due date or last period to jump straight to your week; it runs on your device, nothing is sent or saved.
Sizes and weights are approximate averages — every baby grows differently, and healthy babies span a wide range at every week.
Find your week
Weeks 4-42
The week-by-week guide
Open any week for your baby's development highlights, approximate size, what you may be feeling, and the care checkpoint to have on the calendar. Lengths are crown-to-rump through week 19 and head-to-heel from week 20 — that's why the number jumps there.
First trimester Weeks 4-13
From implantation to fully formed organs — the fastest, most delicate stretch of development, and when the first prenatal visit (8-10 weeks) happens.
Week 4
about the size of a poppy seed ≈ 0.2 cm · under 1 g
About the size of a poppy seed — roughly 0.2 cm long and around under 1 g (approximate averages; healthy babies vary widely).
Your baby this week
- The ball of cells implants in the uterine lining and splits into what becomes the embryo and the placenta.
- The amniotic sac and yolk sac are forming.
- The embryo is a two-layered disc — smaller than a grain of rice.
You may feel
You might not feel anything yet — or notice mild cramping, light spotting, and a missed period. A home pregnancy test can turn positive around now.
Care checkpoint
Take a home pregnancy test if you haven't — and start (or keep taking) a daily prenatal vitamin with at least 400 mcg of folic acid.
Week 5
about the size of a sesame seed ≈ 0.3 cm · under 1 g
About the size of a sesame seed — roughly 0.3 cm long and around under 1 g (approximate averages; healthy babies vary widely).
Your baby this week
- The neural tube — the future brain and spinal cord — begins to form.
- The heart starts as a tiny tube and begins to beat around this week.
- A primitive circulatory system is taking shape.
You may feel
Early symptoms often start now: sore breasts, fatigue, and more frequent trips to the bathroom.
Care checkpoint
Call your provider to book your first prenatal visit — most practices schedule it for weeks 8-10.
Week 6
about the size of a lentil ≈ 0.6 cm · under 1 g
About the size of a lentil — roughly 0.6 cm long and around under 1 g (approximate averages; healthy babies vary widely).
Your baby this week
- The heart beats with a regular rhythm — often visible on an early ultrasound.
- Small buds appear that will become arms and legs.
- Structures for the eyes and inner ears begin to form.
You may feel
Nausea can kick in — at any time of day — along with food aversions and a heightened sense of smell.
Care checkpoint
List every medication and supplement you take so your provider can review them, and stop alcohol, smoking, and recreational drugs now if you haven't.
Week 7
about the size of a blueberry ≈ 1.3 cm · under 1 g
About the size of a blueberry — roughly 1.3 cm long and around under 1 g (approximate averages; healthy babies vary widely).
Your baby this week
- The brain and face are growing quickly — nostrils and the lenses of the eyes are forming.
- Arm buds look like tiny paddles as hands start to form.
You may feel
Fatigue and queasiness often build toward a peak over the next few weeks — small, frequent meals help many people.
Care checkpoint
Write down questions for your first visit: family history, medications, and anything to report like bleeding, pain, or severe vomiting.
Week 8
about the size of a raspberry ≈ 1.6 cm · 1 g
About the size of a raspberry — roughly 1.6 cm long and around 1 g (approximate averages; healthy babies vary widely).
Your baby this week
- Every major organ has started to form.
- Fingers and toes are forming, still webbed.
- The embryo makes tiny movements — far too small to feel.
You may feel
Bloating, tender breasts, and morning sickness are all common; your clothes may start feeling snug before anything shows.
Care checkpoint
First prenatal visit window opens (typically 8-10 weeks per ACOG): health history, blood type and Rh, blood count, and screening for HIV, syphilis, and hepatitis B — often a dating ultrasound too.
Week 9
about the size of a cherry ≈ 2.3 cm · 2 g
About the size of a cherry — roughly 2.3 cm long and around 2 g (approximate averages; healthy babies vary widely).
Your baby this week
- The embryonic tail is gone — your baby looks recognizably human.
- Elbows can bend; fingers and toes are lengthening.
- Essential organs are formed and beginning to function.
You may feel
Mood swings are normal — hormones are surging — and nausea may be at its worst around now.
Care checkpoint
At the first visit, ask about genetic-screening options so you can decide before the testing windows open.
Week 10
about the size of a kumquat ≈ 3.1 cm · 4 g
About the size of a kumquat — roughly 3.1 cm long and around 4 g (approximate averages; healthy babies vary widely).
Your baby this week
- Officially a fetus from this week.
- Fingers and toes have separated, and soft nails begin to form.
- Tooth buds are forming under the gums.
You may feel
You may notice visible veins and a thickening waist; for many, nausea starts to ease over the coming weeks.
Care checkpoint
Cell-free DNA screening (NIPT) can be drawn any time from 10 weeks onward, if you've chosen it.
Week 11
about the size of a fig ≈ 4.1 cm · 7 g
About the size of a fig — roughly 4.1 cm long and around 7 g (approximate averages; healthy babies vary widely).
Your baby this week
- The head makes up about half the body's length.
- External genitals are starting to develop.
- Red blood cells are forming in the liver.
You may feel
Energy may start returning; some people notice more discharge, which is normal if it's clear and mild.
Care checkpoint
First-trimester combined screening (nuchal-translucency scan plus blood work) runs roughly weeks 11-14, if that's your chosen route.
Week 12
about the size of a lime ≈ 5.4 cm · 14 g
About the size of a lime — roughly 5.4 cm long and around 14 g (approximate averages; healthy babies vary widely).
Your baby this week
- Reflexes appear — the mouth makes sucking motions.
- The kidneys are making urine.
- Fingernails and toenails continue to form.
You may feel
Many feel a turning point around now: nausea eases and energy climbs as the first trimester winds down.
Care checkpoint
Routine visit — many practices can find the heartbeat with a handheld Doppler around now.
Week 13
about the size of a pea pod ≈ 7.4 cm · 23 g
About the size of a pea pod — roughly 7.4 cm long and around 23 g (approximate averages; healthy babies vary widely).
Your baby this week
- Vocal cords are forming.
- The intestines, which developed partly inside the umbilical cord, have moved into the abdomen.
- The first faint fingerprints are appearing.
You may feel
You might have noticeably more energy — and a small bump may just be starting to show.
Care checkpoint
Last week of the first trimester. If you're having the NT scan, the window closes about now (around 13w6d).
Second trimester Weeks 14-27
Growth you can see and movement you can feel — plus the anatomy scan (18-22 weeks) and the start of glucose screening (24-28 weeks).
Week 14
about the size of a lemon ≈ 8.7 cm · 43 g
About the size of a lemon — roughly 8.7 cm long and around 43 g (approximate averages; healthy babies vary widely).
Your baby this week
- External sex organs are fully formed.
- Red blood cells are being produced in the spleen.
- Fine, downy hair (lanugo) begins to grow.
You may feel
Welcome to the trimester most people find easiest: appetite often returns, and round-ligament twinges can start.
Care checkpoint
Second trimester begins. Prenatal visits usually run every 4 weeks through week 28.
Week 15
about the size of an apple ≈ 10.1 cm · 70 g
About the size of an apple — roughly 10.1 cm long and around 70 g (approximate averages; healthy babies vary widely).
Your baby this week
- Bones are hardening and show up on ultrasound.
- The scalp hair pattern is set.
- The skin is still so thin that blood vessels show through.
You may feel
A stuffy nose (pregnancy rhinitis) is common — it's hormone-driven and harmless.
Care checkpoint
The quad-screen blood test window runs about weeks 15-22, if you're using it instead of (or alongside) earlier screening.
Week 16
about the size of an avocado ≈ 11.6 cm · 100 g
About the size of an avocado — roughly 11.6 cm long and around 100 g (approximate averages; healthy babies vary widely).
Your baby this week
- The eyes can move slowly behind closed lids.
- The ears are close to their final position.
- Limb movements are becoming coordinated.
You may feel
Your bump likely shows now, and some second-time parents feel the first movements around this week.
Care checkpoint
Routine visit around 16 weeks — ask how to schedule the 18-22-week anatomy scan.
Week 17
about the size of a pear ≈ 13 cm · 140 g
About the size of a pear — roughly 13 cm long and around 140 g (approximate averages; healthy babies vary widely).
Your baby this week
- Fat stores begin to build under the skin.
- Sweat glands are developing.
- The umbilical cord is growing thicker and stronger.
You may feel
Appetite is often up, and you may notice a darker vertical line (linea nigra) forming on your belly.
Care checkpoint
Book the anatomy ultrasound now if it isn't already on the calendar — the 18-22-week window fills up.
Week 18
about the size of a bell pepper ≈ 14.2 cm · 190 g
About the size of a bell pepper — roughly 14.2 cm long and around 190 g (approximate averages; healthy babies vary widely).
Your baby this week
- The ears stand out and your baby may begin to hear.
- A protective myelin coating starts to wrap the nerves.
- Your baby can yawn and hiccup.
You may feel
First flutters (quickening) commonly arrive between 18 and 20 weeks — like bubbles, taps, or popcorn.
Care checkpoint
Anatomy-scan window opens (18-22 weeks): a detailed ultrasound of your baby's organs, growth, and the placenta.
Week 19
about the size of a mango ≈ 15.3 cm · 240 g
About the size of a mango — roughly 15.3 cm long and around 240 g (approximate averages; healthy babies vary widely).
Your baby this week
- Vernix caseosa, a protective waxy coating, covers the skin.
- Brain areas for touch, taste, hearing, sight, and smell are specializing.
- Movements are getting strong enough for you to notice.
You may feel
Round-ligament pain — a brief, sharp twinge in the side when you change position — is common.
Care checkpoint
Anatomy-scan window — and the stretch when many first-time parents start feeling movement.
Week 20
about the size of a banana ≈ 25.6 cm · 300 g
About the size of a banana — roughly 25.6 cm long and around 300 g (approximate averages; healthy babies vary widely).
Your baby this week
- Your baby can swallow and is producing meconium, the first stool.
- You're halfway — movement becomes more regular and noticeable.
- Nails are growing toward the fingertips.
You may feel
Halfway there. Movements become more distinct, and you may be sleeping better on your side with a pillow for support.
Care checkpoint
Halfway point. If the anatomy scan hasn't happened yet, it should be scheduled within the next two weeks.
Week 21
about the size of a carrot ≈ 26.7 cm · 360 g
About the size of a carrot — roughly 26.7 cm long and around 360 g (approximate averages; healthy babies vary widely).
Your baby this week
- Eyebrows and eyelashes are in place.
- Taste buds are forming.
- Movements have gone from flutters to real kicks and rolls.
You may feel
Kicks may soon be feelable from the outside, and painless, irregular tightenings (Braxton Hicks) can begin.
Care checkpoint
Routine visit month — a good time to start looking into childbirth-education classes.
Week 22
about the size of a papaya ≈ 27.8 cm · 430 g
About the size of a papaya — roughly 27.8 cm long and around 430 g (approximate averages; healthy babies vary widely).
Your baby this week
- The eyes are fully formed, though the irises still lack pigment.
- A grasp reflex is developing — your baby can grip the umbilical cord.
- Loud sounds can trigger a startle.
You may feel
Mild swelling in the feet and ankles can start — water, movement, and putting your feet up all help.
Care checkpoint
Anatomy-scan window closes this week — make sure it's done or booked.
Week 23
about the size of a grapefruit ≈ 28.9 cm · 500 g
About the size of a grapefruit — roughly 28.9 cm long and around 500 g (approximate averages; healthy babies vary widely).
Your baby this week
- The lungs are starting to make surfactant, the substance that will let the air sacs inflate after birth.
- Skin is still wrinkled and translucent-red.
- Hearing sharpens — your voice is becoming familiar.
You may feel
You may notice your baby jump at a sudden loud noise.
Care checkpoint
Register for childbirth, breastfeeding, or newborn-care classes, and tour your delivery hospital or birth center if you can.
Week 24
about the size of an ear of corn ≈ 30 cm · 600 g
About the size of an ear of corn — roughly 30 cm long and around 600 g (approximate averages; healthy babies vary widely).
Your baby this week
- Air sacs (alveoli) are developing in the lungs.
- The inner ear is fully developed, giving your baby a sense of movement and balance.
- Sleep and wake cycles are becoming more defined.
You may feel
Backache and leg cramps are common as the bump grows and your posture shifts.
Care checkpoint
Glucose-screening window opens: ACOG recommends screening for gestational diabetes at 24-28 weeks.
Week 25
about the size of a rutabaga ≈ 34.6 cm · 660 g
About the size of a rutabaga — roughly 34.6 cm long and around 660 g (approximate averages; healthy babies vary widely).
Your baby this week
- The nostrils begin to open, and your baby practices breathing motions with amniotic fluid.
- Familiar voices may get a wiggle in response.
- Growing fat is starting to smooth the wrinkled skin.
You may feel
Heartburn often picks up — smaller meals and staying upright after eating help.
Care checkpoint
Get the glucose screen on the calendar if it isn't done, and ask about the Tdap vaccine coming up at 27-36 weeks.
Week 26
about the size of a head of lettuce ≈ 35.6 cm · 760 g
About the size of a head of lettuce — roughly 35.6 cm long and around 760 g (approximate averages; healthy babies vary widely).
Your baby this week
- The eyes begin to open for the first time.
- The lungs keep building surfactant.
- You may feel rhythmic twitches — hiccups.
You may feel
Those small rhythmic movements you feel are often baby hiccups — completely normal.
Care checkpoint
The glucose screen should be done by 28 weeks; if you're Rh-negative, Rho(D) immune globulin is typically given around week 28.
Week 27
about the size of a cauliflower ≈ 36.6 cm · 875 g
About the size of a cauliflower — roughly 36.6 cm long and around 875 g (approximate averages; healthy babies vary widely).
Your baby this week
- The eyes open and close, and your baby has sleep cycles that include REM sleep.
- Regular practice-breathing movements continue.
- The brain is in a stretch of very rapid growth.
You may feel
Sleep can get tricky from here — a pillow between the knees helps many people.
Care checkpoint
Tdap vaccine window opens (27-36 weeks): it passes whooping-cough protection to your baby, and earlier in the window is better.
Third trimester Weeks 28-42
Weight gain, lung maturity, kick counts, Tdap and GBS — and the term bands that define early, full, late, and postterm.
Week 28
about the size of an eggplant ≈ 37.6 cm · 1,000 g
About the size of an eggplant — roughly 37.6 cm long and around 1,000 g (approximate averages; healthy babies vary widely).
Your baby this week
- Eyelashes are formed and the eyes are partly open.
- The central nervous system can direct rhythmic breathing movements and better control body temperature.
- Kicks are strong and regular — which is exactly what kick counting tracks.
You may feel
Shortness of breath on exertion is common as the uterus rises; movement patterns become predictable now.
Care checkpoint
Third trimester. Visits usually move to every 2 weeks; start daily kick counts, and get a flu shot if it's flu season.
Week 29
about the size of a butternut squash ≈ 38.6 cm · 1,150 g
About the size of a butternut squash — roughly 38.6 cm long and around 1,150 g (approximate averages; healthy babies vary widely).
Your baby this week
- Bones are fully formed, though still soft and pliable.
- Your baby kicks, stretches, and makes grasping motions.
- A period of rapid brain growth is under way.
You may feel
Leg cramps and vivid dreams are common third-trimester companions.
Care checkpoint
Do kick counts at about the same time each day — and call your provider the same day if movement drops noticeably.
Week 30
about the size of a cabbage ≈ 39.9 cm · 1,320 g
About the size of a cabbage — roughly 39.9 cm long and around 1,320 g (approximate averages; healthy babies vary widely).
Your baby this week
- The eyes can open wide.
- Red blood cell production has shifted to the bone marrow.
- The fine lanugo hair is starting to disappear.
You may feel
Fatigue often returns, and your balance shifts as your center of gravity moves forward.
Care checkpoint
Routine visit — and a good week to start the baby-gear and parental-leave checklists.
Week 31
about the size of a coconut ≈ 41.1 cm · 1,500 g
About the size of a coconut — roughly 41.1 cm long and around 1,500 g (approximate averages; healthy babies vary widely).
Your baby this week
- Rapid weight gain is under way — much of the remaining weeks is about growing.
- Movements are strong; you may see an elbow or heel travel across your belly.
- The lungs and brain continue maturing quickly.
You may feel
Braxton Hicks may get more noticeable — irregular and easing with rest, unlike real labor.
Care checkpoint
Draft your birth preferences so you can talk them through at upcoming visits.
Week 32
about the size of a jicama ≈ 42.4 cm · 1,700 g
About the size of a jicama — roughly 42.4 cm long and around 1,700 g (approximate averages; healthy babies vary widely).
Your baby this week
- Fingernails have reached the fingertips.
- The downy lanugo is falling away.
- Practice-breathing motions are now regular.
You may feel
You may feel breathless and find yourself back to frequent bathroom trips as space gets tight.
Care checkpoint
If you haven't had the Tdap vaccine yet this pregnancy, arrange it now — the window closes at 36 weeks.
Week 33
about the size of a pineapple ≈ 43.7 cm · 1,920 g
About the size of a pineapple — roughly 43.7 cm long and around 1,920 g (approximate averages; healthy babies vary widely).
Your baby this week
- The pupils constrict and dilate in response to light.
- Bones keep hardening — but the skull stays soft and flexible for birth.
- Fat keeps rounding out the arms and legs.
You may feel
Pelvic pressure and an achy lower back are common as your baby grows and settles lower.
Care checkpoint
Ask your provider about your baby's position — most turn head-down over the coming weeks.
Week 34
about the size of a cantaloupe ≈ 45 cm · 2,150 g
About the size of a cantaloupe — roughly 45 cm long and around 2,150 g (approximate averages; healthy babies vary widely).
Your baby this week
- The protective vernix coating thickens.
- Most babies settle head-down around now.
- Toenails have reached the tips of the toes.
You may feel
Colostrum may leak, and ankles may swell by evening. Sudden swelling of the face or hands is a call-your-provider symptom.
Care checkpoint
Pre-register at your hospital or birth center, and get the car seat installed and checked.
Week 35
about the size of a honeydew melon ≈ 46.2 cm · 2,380 g
About the size of a honeydew melon — roughly 46.2 cm long and around 2,380 g (approximate averages; healthy babies vary widely).
Your baby this week
- The kidneys are fully developed.
- The liver can process some waste products.
- Space is tight — movements feel like rolls and stretches, but should stay just as frequent.
You may feel
Sleep is hard and movements feel different — more rolling, less jabbing — but the daily count should hold steady.
Care checkpoint
Pack the hospital bag. Prenatal visits move to weekly starting at 36 weeks.
Week 36
about the size of a head of romaine lettuce ≈ 47.4 cm · 2,620 g
About the size of a head of romaine lettuce — roughly 47.4 cm long and around 2,620 g (approximate averages; healthy babies vary widely).
Your baby this week
- Your baby is gaining roughly 30 g (about an ounce) a day.
- The skin is getting smoother and plumper.
- Your baby may drop lower into your pelvis (lightening).
You may feel
If your baby drops, breathing gets easier while bathroom trips increase — a classic trade.
Care checkpoint
The group B strep (GBS) swab happens at 36-37 weeks (ACOG: 36w0-37w6) — and this week is the Tdap deadline if it isn't done.
Week 37
about the size of a bunch of Swiss chard ≈ 48.6 cm · 2,860 g
About the size of a bunch of Swiss chard — roughly 48.6 cm long and around 2,860 g (approximate averages; healthy babies vary widely).
Your baby this week
- Early term. Coordination has arrived — your baby can grasp firmly.
- Breathing, sucking, and swallowing are being practiced together: the exact skills needed for feeding.
- Fat keeps building for temperature control after birth.
You may feel
You may lose the mucus plug, and bursts of nesting energy are common.
Care checkpoint
Early term begins (37w0-38w6). Know the signs of labor and when to call: regular contractions, waters breaking, bleeding, or reduced movement.
Week 38
about the size of a leek ≈ 49.8 cm · 3,080 g
About the size of a leek — roughly 49.8 cm long and around 3,080 g (approximate averages; healthy babies vary widely).
Your baby this week
- The brain and lungs are still maturing rapidly — and keep developing after birth.
- Lanugo is mostly gone.
- Meconium is accumulating in the intestines.
You may feel
Pelvic pressure and sporadic contractions are typical — start timing them when they feel regular.
Care checkpoint
Weekly visits continue. Finalize who you'll call and your route to the hospital or birth center.
Week 39
about the size of a mini watermelon ≈ 50.7 cm · 3,290 g
About the size of a mini watermelon — roughly 50.7 cm long and around 3,290 g (approximate averages; healthy babies vary widely).
Your baby this week
- Full term: organs are developed and ready for life outside.
- Fat keeps building to help hold body temperature after birth.
- The grasp is strong — you'll feel it soon.
You may feel
Watch for real labor: contractions that get regular, longer, and stronger, or your waters breaking.
Care checkpoint
Full term (39w0-40w6) — the band with the best outcomes for delivery. Nothing elective is scheduled before 39 weeks.
Week 40
about the size of a small pumpkin ≈ 51.2 cm · 3,460 g
About the size of a small pumpkin — roughly 51.2 cm long and around 3,460 g (approximate averages; healthy babies vary widely).
Your baby this week
- An average newborn weighs about 3.5 kg and measures about 51 cm — with a wide healthy range around both.
- The skull bones remain unfused so the head can mold through the birth canal.
- Position and station are what your provider is checking now.
You may feel
Waiting past the date is normal — only about 1 in 20 babies arrives on it. Stay as active as is comfortable and keep tracking movement.
Care checkpoint
Your due date. Your provider may discuss extra monitoring or a membrane sweep if labor hasn't started.
Week 41
about the size of a pumpkin ≈ 51.7 cm · 3,600 g
About the size of a pumpkin — roughly 51.7 cm long and around 3,600 g (approximate averages; healthy babies vary widely).
Your baby this week
- Your baby continues to gain weight.
- Vernix and lanugo are mostly gone.
- Monitoring keeps an eye on amniotic fluid and how the placenta is doing.
You may feel
Frustration is completely normal at this point — keep every monitoring appointment this week.
Care checkpoint
Late term (41w0-41w6): expect extra monitoring (non-stress tests, fluid checks) and a conversation about induction.
Week 42
about the size of a watermelon ≈ 51.5 cm · 3,690 g
About the size of a watermelon — roughly 51.5 cm long and around 3,690 g (approximate averages; healthy babies vary widely).
Your baby this week
- Postterm. Skin may be dry or peeling at birth after the long soak.
- Nails can be surprisingly long.
- Placenta function can decline past 42 weeks — the main reason induction is recommended.
You may feel
Hang in there — your provider will map out the induction timing and monitoring plan with you.
Care checkpoint
Postterm (42w0+): induction is typically recommended at or before now, per ACOG guidance.
Before you compare
Every baby grows differently
The lengths and weights on this page are approximate averages — close to the 50th percentile of published fetal-growth references. At any given week, perfectly healthy babies routinely measure anywhere from about the 10th to the 90th percentile, which by the third trimester can mean a spread of many hundreds of grams between two thriving babies.
That means nothing on this page can tell you whether your baby is growing well — and neither can comparing one scan estimate to a chart. Growth is assessed by your provider, from your own ultrasound measurements, in context and over time. If a scan report ever worries you, ask your provider to walk you through it rather than measuring against averages here or anywhere else.
Reference
Growth at a glance
The same approximate averages as the guide above, in one scannable chart. Lengths are crown-to-rump through week 19 and head-to-heel from week 20; weights round to conservative published averages.
| Week | About the size of | Length (approx.) | Weight (approx.) |
|---|---|---|---|
| 4 | a poppy seed | 0.2 cm | under 1 g |
| 5 | a sesame seed | 0.3 cm | under 1 g |
| 6 | a lentil | 0.6 cm | under 1 g |
| 7 | a blueberry | 1.3 cm | under 1 g |
| 8 | a raspberry | 1.6 cm | 1 g |
| 9 | a cherry | 2.3 cm | 2 g |
| 10 | a kumquat | 3.1 cm | 4 g |
| 11 | a fig | 4.1 cm | 7 g |
| 12 | a lime | 5.4 cm | 14 g |
| 13 | a pea pod | 7.4 cm | 23 g |
| 14 | a lemon | 8.7 cm | 43 g |
| 15 | an apple | 10.1 cm | 70 g |
| 16 | an avocado | 11.6 cm | 100 g |
| 17 | a pear | 13 cm | 140 g |
| 18 | a bell pepper | 14.2 cm | 190 g |
| 19 | a mango | 15.3 cm | 240 g |
| 20 | a banana | 25.6 cm | 300 g |
| 21 | a carrot | 26.7 cm | 360 g |
| 22 | a papaya | 27.8 cm | 430 g |
| 23 | a grapefruit | 28.9 cm | 500 g |
| 24 | an ear of corn | 30 cm | 600 g |
| 25 | a rutabaga | 34.6 cm | 660 g |
| 26 | a head of lettuce | 35.6 cm | 760 g |
| 27 | a cauliflower | 36.6 cm | 875 g |
| 28 | an eggplant | 37.6 cm | 1,000 g |
| 29 | a butternut squash | 38.6 cm | 1,150 g |
| 30 | a cabbage | 39.9 cm | 1,320 g |
| 31 | a coconut | 41.1 cm | 1,500 g |
| 32 | a jicama | 42.4 cm | 1,700 g |
| 33 | a pineapple | 43.7 cm | 1,920 g |
| 34 | a cantaloupe | 45 cm | 2,150 g |
| 35 | a honeydew melon | 46.2 cm | 2,380 g |
| 36 | a head of romaine lettuce | 47.4 cm | 2,620 g |
| 37 | a bunch of Swiss chard | 48.6 cm | 2,860 g |
| 38 | a leek | 49.8 cm | 3,080 g |
| 39 | a mini watermelon | 50.7 cm | 3,290 g |
| 40 | a small pumpkin | 51.2 cm | 3,460 g |
| 41 | a pumpkin | 51.7 cm | 3,600 g |
| 42 | a watermelon | 51.5 cm | 3,690 g |
Approximate ~50th-percentile averages compiled from standard published fetal-growth references (including the WHO fetal growth charts). Healthy babies span a wide percentile range at every week — this chart cannot be used to judge growth, and size here is never a diagnosis.
How this guide works
How the weeks are counted — and where the milestones come from
Every week number here is gestational age: counted from the first day of your last menstrual period, the way medicine counts everywhere. That means the clock starts about two weeks before conception, your baby is roughly two weeks younger than the week number, and the guide begins at week 4 — implantation, and about when a home test can first turn positive. The trimesters split at the end of week 13 and week 27.
The development highlights follow NIH MedlinePlus fetal-development milestones; the care checkpoints follow ACOG's prenatal schedule — first visit at 8-10 weeks, NIPT from 10 weeks, anatomy scan at 18-22 weeks, glucose screening at 24-28 weeks, Tdap at 27-36 weeks, the GBS swab at 36-37 weeks, and the early/full/late/postterm bands at the end. Your own schedule may differ; your provider tailors it to you.
The sizes are there for wonder, not for judgment: they're conservative published averages, and your baby's actual growth is assessed by your provider from your own scans — never from a chart.
Next steps
Related tools
How far along am I?
Work out your exact week and day from whichever date you know.
Prenatal visit schedule
Every visit, test, and vaccine window from positive test to delivery.
Due date calculator
Date your pregnancy from your last period, conception, IVF, or a scan.
All pregnancy tools
The full suite — from timing conception to tracking every week.
Sources
Where this comes from
Development milestones follow NIH MedlinePlus fetal-development material and ACOG's patient guidance on how a fetus grows. Care checkpoints follow ACOG's prenatal testing and visit milestones. Approximate lengths and weights are conservative averages compiled from standard published fetal-growth references, including the WHO fetal growth charts. We apply published references — we don't invent our own numbers.
Medically Reviewed & Fact-Checked · Updated
Reviewed by EasySTD Editorial Team
Compiled and checked by EasySTD's editorial team against CDC and public-health sources. This is educational information, not a substitute for advice from a licensed clinician. Our editorial guidelines →
4 Sources
Data & references
- NIH MedlinePlus: Fetal developmenthttps://medlineplus.gov/ency/article/002398.htm
- ACOG: How your fetus grows during pregnancyhttps://www.acog.org/womens-health/faqs/how-your-fetus-grows-during-pregnancy
- ACOG: Routine tests during pregnancyhttps://www.acog.org/womens-health/faqs/routine-tests-during-pregnancy
- WHO fetal growth charts (Kiserud T et al., PLoS Medicine, 2017) — reference fetal size by weekhttps://pubmed.ncbi.nlm.nih.gov/28118360/
EasySTD is an information and comparison directory, not a healthcare provider. This guide is general educational information based on published references: it is not medical advice or a diagnosis, and it does not create a doctor-patient relationship. Sizes are approximate averages and can never assess your baby's growth — your provider and your own prenatal visits do that.
Good to Know
Pregnancy weeks: frequently asked questions
How the weeks are counted, how accurate the sizes are, when the big tests happen, when you'll feel movement, and what the term bands mean.
How accurate are the week-by-week sizes and weights?
They're approximate population averages — roughly the 50th percentile from published fetal-growth references — not targets your baby is supposed to hit. Perfectly healthy babies at the same week routinely span from about the 10th to the 90th percentile, which can mean hundreds of grams of difference in the third trimester. The fruit comparisons are just a friendly way to picture scale. None of this can be used to judge how your baby is doing: only your provider, reading your own ultrasound measurements in context and over time, can assess growth. A single size estimate — here or on a scan — is never a diagnosis.
How are pregnancy weeks counted, and why does this guide start at week 4?
Pregnancy is counted in gestational age: from the first day of your last menstrual period, not from conception. That means the count starts about two weeks before conception actually happens, so your baby is roughly two weeks younger than the week number. Weeks 1-2 are pre-conception and week 3 is fertilization and travel to the uterus — there's essentially nothing to track day-to-day until implantation completes around week 4, which is also about when a home test can first turn positive. That's why this guide, like most, begins there. Every week number your provider and your apps use is gestational age, so they all line up.
What are the key appointments and tests, week by week?
The big ACOG-aligned milestones: a first prenatal visit at about 8-10 weeks (history, blood type, labs, infection screening, often a dating ultrasound); cell-free DNA screening (NIPT) any time from 10 weeks if you choose it; the nuchal-translucency scan at about 11-14 weeks; the anatomy ultrasound at 18-22 weeks; glucose screening for gestational diabetes at 24-28 weeks; the Tdap vaccine between 27 and 36 weeks; and the group B strep swab at 36-37 weeks. Visits typically run every 4 weeks to 28, every 2 weeks to 36, then weekly. Your own schedule may differ — your provider tailors it to you.
When will I feel the baby move?
Most first-time parents feel the first movements — called quickening — between 18 and 20 weeks; people who've been pregnant before often notice them earlier, sometimes around 16 weeks. Early movement feels like flutters, bubbles, or popcorn, and it's easy to mistake for digestion at first. It becomes unmistakable kicks and rolls through the second trimester. From 28 weeks, movement patterns are established enough that many providers suggest daily kick counts at a consistent time. The pattern matters more than any single quiet hour — but a real, sustained drop in movement is always worth a same-day call to your provider.
What do early term, full term, late term, and postterm mean?
ACOG divides the weeks around the due date into named bands because outcomes differ across them. Early term is 37w0 through 38w6 — babies born here usually do well, but a bit more maturing still helps. Full term is 39w0 through 40w6, the band with the best outcomes, which is why nothing elective is scheduled before 39 weeks. Late term is 41w0 through 41w6, when extra monitoring typically starts. Postterm is 42 weeks and beyond, where induction is generally recommended because placenta function can decline. Your due date sits in the middle of all this — a planning anchor, not a deadline.
Is what I enter here private?
Yes. The week finder runs entirely in your browser: any date you enter is used on your own device to compute a week number and is never sent to a server, saved, or shared — close the tab and it's gone. We treat reproductive data as sensitive by default. The guide itself is general educational information drawn from NIH MedlinePlus fetal-development material and ACOG prenatal-care milestones; it isn't medical advice, and your own prenatal schedule and any questions about your baby's growth belong with your provider.
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