Pregnancy guidelines week by week! Just Follow To Know the Pregnancy stages!
A full pregnancy lasts about 40 weeks, and it is counted from the first day of your last menstrual period, not from the day you conceive. Those 40 weeks are split into three trimesters. Your baby changes every week, and so does your body, which is why most people want a clear picture of what to expect and what to do at each stage.
This guide gives you the full map. It explains how weeks are counted, what happens in each trimester, how your baby grows from week 1 to week 40, and the nutrition, sleep, exercise and safety advice that applies throughout. Use the week-by-week table to jump to the detailed guide for the week you are in.
Short Answer: Pregnancy lasts about 40 weeks, divided into the first trimester (weeks 1 to 13), the second trimester (weeks 14 to 27) and the third trimester (weeks 28 to birth). Take folic acid early, eat a varied diet, avoid alcohol and smoking, attend your antenatal checkups, and sleep on your side in the later weeks. Contact your doctor straight away if you have heavy bleeding, severe pain or your baby moves less than usual.
Note: This article is general information and not medical advice. Pregnancy care differs between countries, health systems and individual health conditions. Scan timings, vaccines and weight targets vary, so follow the advice of your own doctor or midwife, especially if you have a health condition or a high-risk pregnancy.
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How pregnancy weeks are counted
Doctors start the count on the first day of your last period, which is called the LMP. This is because most people know that date, while the day of conception is hard to pin down. It also means you are described as pregnant for about two weeks before you have actually conceived. Conception usually happens in week 3, so the baby’s real age is about two weeks less than the week number.
To work out your due date, add 280 days (40 weeks) to the first day of your last period. A quick way is to add nine months and seven days. An early ultrasound can adjust the date if your cycle is irregular. A due date is an estimate. Only a small share of babies arrive on that exact day, and birth is considered:
- Early term: 37 weeks to 38 weeks 6 days
- Full term: 39 weeks to 40 weeks 6 days
- Late term: 41 weeks to 41 weeks 6 days
- Post-term: 42 weeks and beyond
Pregnancy is often described in months, but weeks are more precise. Roughly, month 1 covers weeks 1 to 4, month 2 weeks 5 to 8, month 3 weeks 9 to 13, and so on until month 9.
The three trimesters at a glance
| Trimester | Weeks | What happens | What you may feel |
|---|---|---|---|
| First | 1 to 13 | Conception, implantation, and the formation of all major organs. The heart starts to beat. | Missed period, tiredness, nausea, tender breasts, frequent urination |
| Second | 14 to 27 | Rapid growth. Bones harden, movements begin and the baby can hear. | More energy, a growing bump, first movements, backache, heartburn |
| Third | 28 to birth | Weight gain, lung and brain maturation, and the baby moves into position. | Shortness of breath, swelling, trouble sleeping, practice contractions |
The first trimester carries the highest risk of miscarriage, and it is when organs form, so healthy habits matter most early. The second is often the most comfortable. The third prepares your body and your baby for birth.
Week-by-week guide
Each week below has a short summary. Size comparisons are rough averages, and real measurements vary between babies and between sources, so do not worry if your baby measures a little ahead or behind. Click the week to read the full guide.
First trimester
| Week | Baby size | What is happening |
|---|---|---|
| Week 1 | No baby yet | Your period. The count begins. |
| Week 2 | No baby yet | An egg matures and ovulation approaches. |
| Week 3 | A tiny cluster of cells | Fertilization and cell division. |
| Week 4 | Poppy seed | Implantation. A pregnancy test may turn positive. |
| Week 5 | Sesame seed | The neural tube forms, and the heart tube begins. |
| Week 6 | Lentil | The heartbeat can often be seen on an early scan. |
| Week 7 | Blueberry | Arm and leg buds appear, and the brain grows quickly. |
| Week 8 | Raspberry | Fingers and toes begin to form. |
| Week 9 | Grape | The heart chambers form, and the facial features develop. |
| Week 10 | Strawberry | Vital organs are in place. The fetal stage begins. |
| Week 11 | Fig | Fingernails start to form. |
| Week 12 | Lime | Reflexes develop, and the kidneys start working. |
| Week 13 | Peach | Fingerprints form. The first trimester ends. |
Second trimester
| Week | Baby size | What is happening |
|---|---|---|
| Week 14 | Lemon | Facial muscles move, and the neck lengthens. |
| Week 15 | Apple | Bones harden, and the baby can sense light. |
| Week 16 | Avocado | The eyes move, and early movements may be felt. |
| Week 17 | Pomegranate | Fat begins to form under the skin. |
| Week 18 | Bell pepper | The ears are in position, and the baby may hear sounds. |
| Week 19 | Mango | A protective coating called vernix forms on the skin. |
| Week 20 | Banana | Halfway point. The anatomy scan is often done around now. |
| Week 21 | Carrot | The baby swallows, and movements become stronger. |
| Week 22 | Papaya | Eyebrows form, and the sense of touch develops. |
| Week 23 | Grapefruit | Hearing sharpens, and the lungs develop. |
| Week 24 | Corn on the cob | The lungs form air sacs. This is a common viability threshold in many countries. |
| Week 25 | Cauliflower | The baby responds to your voice. |
| Week 26 | Lettuce head | The eyes begin to open. |
| Week 27 | Rutabaga | Sleep and wake cycles develop. The second trimester ends. |
Third trimester
| Week | Baby size | What is happening |
|---|---|---|
| Week 28 | Eggplant | The eyes open, and the brain grows quickly. |
| Week 29 | Butternut squash | The bones are fully formed but still soft. |
| Week 30 | Cabbage | The brain develops grooves and folds. |
| Week 31 | Coconut | The baby’s senses are working together. |
| Week 32 | Squash | The baby practices breathing movements. |
| Week 33 | Pineapple | The bones harden except the skull. |
| Week 34 | Cantaloupe | The lungs keep maturing. |
| Week 35 | Honeydew melon | The kidneys are fully developed. |
| Week 36 | Romaine lettuce | The baby may move head down into the pelvis. |
| Week 37 | Winter melon | Early term begins. |
| Week 38 | Leek | The organs are ready for life outside the womb. |
| Week 39 | Mini watermelon | Full term begins. |
| Week 40 | Pumpkin | Your estimated due date. |
Nutrition and supplements
You do not need a special diet, and you do not need to eat for two. Most people need only a small increase in calories in the second and third trimesters. The quality of what you eat matters more than the amount.
Build your meals around vegetables and fruit, whole grains, protein from eggs, beans, lentils, fish and poultry, dairy or fortified alternatives, and plenty of water. Smaller, more frequent meals can help with nausea and heartburn.
Supplements to discuss with your doctor:
- Folic acid. It lowers the risk of neural tube defects such as spina bifida. Most health authorities recommend 400 micrograms (0.4 mg) a day before conception and through early pregnancy. Some people need a higher dose on prescription. See the CDC folic acid page for details.
- Iron. Needs rise in pregnancy to support your growing blood supply. Your doctor may test your blood and suggest a supplement if you are low.
- Vitamin D. Some health authorities, such as the NHS, recommend a daily supplement.
- Calcium and iodine. Most people get enough from food, but ask your doctor if your diet is limited.
Check that any prenatal vitamin you buy is suitable for pregnancy, and do not take high-dose supplements, especially vitamin A, unless a doctor advises it.
Foods and habits to avoid
- Alcohol. No amount is known to be safe in pregnancy.
- Smoking and vaping. These raise the risk of miscarriage, premature birth and low birth weight. Ask your doctor for help to stop.
- Raw or undercooked meat, fish and eggs. They can carry bacteria and parasites.
- Unpasteurized milk and soft cheeses made from it. They can carry listeria.
- High-mercury fish, such as shark, swordfish and king mackerel.
- Liver and high-dose vitamin A supplements.
- Too much caffeine. Keep it under 200 mg a day, about two cups of instant coffee.
- Hot tubs and saunas, because a large rise in body temperature is not advised, especially early on.
- Unchecked medicines. Ask a pharmacist or doctor before taking any medicine or herbal product.
Exercise during pregnancy
For most healthy pregnancies, regular exercise is good for you and your baby. It helps with energy, mood, sleep and back pain, and it can lower the risk of gestational diabetes. Health authorities such as WHO and ACOG suggest around 150 minutes of moderate activity a week for most pregnant people.
Good choices include walking, swimming, stationary cycling, prenatal yoga and gentle strength work. Avoid contact sports, activities with a high risk of falling, scuba diving and hot yoga. After the first trimester, avoid exercises that need you to lie flat on your back for long periods. Stop and call your doctor if you have chest pain, dizziness, vaginal bleeding, fluid leaking or regular painful contractions. If you have a condition such as high blood pressure or a low-lying placenta, ask your doctor what is safe for you.
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Which sleep position is best
Sleeping on your side is the usual advice, and the left side is often suggested because it may improve blood flow. Either side is fine. In the first trimester, any position is comfortable and safe.
From about week 28, many health bodies advise going to sleep on your side and not on your back. Research has linked going to sleep on the back in late pregnancy with a higher risk of stillbirth, though the absolute risk is small. You do not need to worry about waking up on your back, since it is the position you fall asleep in that is advised. A pillow between your knees and one behind your back can help you stay on your side. A body pillow works well too.
How much weight should you gain
Recommended weight gain depends on your weight before pregnancy. The figures below come from guidance used widely in the United States and apply to a single baby. They are a guide, not a target to hit exactly, so talk to your doctor about your own range.
| Pre-pregnancy BMI | Suggested total gain |
|---|---|
| Under 18.5 (underweight) | 12.5 to 18 kg (28 to 40 lb) |
| 18.5 to 24.9 (normal) | 11.5 to 16 kg (25 to 35 lb) |
| 25 to 29.9 (overweight) | 7 to 11.5 kg (15 to 25 lb) |
| 30 or more (obese) | 5 to 9 kg (11 to 20 lb) |
Twin pregnancies and some health conditions have different ranges. Gain is usually small in the first trimester and steadier after that.
Antenatal checkups and tests
The schedule differs by country, but a typical pattern looks like this.
- First visit, about 8 to 10 weeks. Medical history, blood pressure, blood tests and a plan for your care.
- Dating or first trimester scan, about 11 to 14 weeks. It checks the due date and, where offered, screens for conditions such as Down syndrome.
- Anatomy scan, about 18 to 22 weeks. It checks the baby’s growth and organs, and it may show the baby’s sex if you want to know.
- Glucose test, about 24 to 28 weeks. It checks for gestational diabetes.
- Vaccines. Ask your doctor about the flu vaccine, the whooping cough (Tdap) vaccine in the third trimester and any other vaccines offered in your country.
- Late pregnancy checks, including blood pressure, urine tests, measuring your bump and checking the baby’s position.
Later visits usually become more frequent as the due date nears. Keep all appointments, and write down questions in advance.
Warning signs that need urgent care
Contact your doctor or go to hospital straight away if you have:
- Vaginal bleeding, especially heavy bleeding or bleeding with pain
- Severe or constant abdominal pain
- A severe headache, vision changes or sudden swelling of your face, hands or feet, which can be signs of pre-eclampsia
- Fluid leaking from the vagina
- A fever or severe, ongoing vomiting that stops you keeping fluids down
- Regular contractions before 37 weeks
- Fewer movements from your baby than usual, once you have felt a regular pattern. Do not wait until the next day. Call right away
Trust your instincts. If something feels wrong, getting checked is never a waste of anyone’s time.
Your emotional health
Pregnancy brings hormonal changes and big life changes, so mood swings, worry and tearfulness are common. Depression and anxiety also happen during pregnancy, not only after birth. Tell your doctor or midwife if you feel persistently low, hopeless, very anxious or unable to enjoy things for two weeks or more. These conditions are common and treatable, and getting help protects both you and your baby. Talking with your partner, family and friends, and sharing your plans for birth, can also ease stress.
Do and don’t summary
| Do | Don’t |
|---|---|
| Take folic acid before conception and in early pregnancy | Take new medicines or supplements without checking |
| Attend all antenatal appointments | Drink alcohol or smoke |
| Eat a varied, balanced diet and drink water | Eat raw meat, raw eggs or unpasteurized dairy |
| Stay active with gentle exercise | Lie flat on your back to sleep after about 28 weeks |
| Sleep on your side in later pregnancy | Ignore bleeding, severe pain or reduced movements |
| Ask questions and share worries | Rely on social media for medical advice |
FAQ
How many weeks long is a pregnancy?
A full pregnancy lasts about 40 weeks, counted from the first day of your last period. Because conception happens around week 3, your baby develops for roughly 38 weeks. Birth between 37 and 42 weeks is considered normal, and 39 to 40 weeks is full term.
How many trimesters are there and when does each start?
There are three. The first trimester runs from week 1 to the end of week 13, the second from week 14 to the end of week 27, and the third from week 28 until birth. Some sources use slightly different cutoffs, so ask your doctor which they use.
When can I feel my baby move?
First-time parents often feel movements, called quickening, between weeks 18 and 25. If you have had a baby before, you may feel them sooner, at around 16 weeks. Early movements feel like flutters or bubbles. They become stronger and more regular over time.
Which sleep position is best during pregnancy?
Sleeping on your side, either side, is the usual advice, and the left side is often suggested. From about 28 weeks, health bodies recommend going to sleep on your side and not your back. Pillows between your knees and behind your back make it easier.
What foods should I avoid during pregnancy?
Avoid alcohol, raw or undercooked meat, fish and eggs, unpasteurized milk and soft cheeses made from it, high-mercury fish such as shark and swordfish, and liver. Limit caffeine to about 200 mg a day. Ask your doctor if you have allergies or a health condition.
How much folic acid do I need?
Most health authorities recommend 400 micrograms (0.4 mg) daily, starting before conception and continuing through early pregnancy. Some people, such as those with diabetes or a past pregnancy affected by a neural tube defect, need a higher prescribed dose. Ask your doctor.
When should I go to the hospital?
Go straight away for heavy bleeding, severe pain, fluid leaking, a severe headache with vision changes, fever, regular contractions before 37 weeks or fewer baby movements than usual. At full term, call your maternity unit when contractions become regular and strong, or if your waters break.
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