Pregnancy Week by Week: A Complete Trimester-by-Trimester Guide
Doctors count pregnancy from the first day of the last period, so the due date falls at 40 weeks.
A pregnancy lasts about 40 weeks, and almost every one of them brings something new: a symptom, a scan, a milestone, a worry. Many women arrive at my clinic with a notebook full of questions. What should I be feeling now? Is it normal that my baby has not moved yet? When is the next test due?
This guide walks through the whole journey, week by week, grouped by trimester. It tells you what is happening with your baby, what changes to expect in your body, which tests are due and what deserves a call to your doctor. It is a general guide, and every pregnancy is a little different, so please treat the weeks as approximate and your own doctor's advice as the final word.
If you are looking for a gynaecologist in Noida for antenatal care, details are at the end.
How pregnancy weeks are counted
Doctors count pregnancy from the first day of your last menstrual period (LMP), not from conception. This means that at "week 4," you have only just missed a period, and conception actually happened around week 2. The due date (EDD) is calculated as 40 weeks from LMP, or adjusted by an early scan. Only about 4 in 100 babies arrive on the actual due date. Anywhere from 37 to 42 weeks is considered normal.
First trimester (weeks 1 to 13)
The first trimester is the time of fastest change. The baby's organs form, and your body adapts, often with fatigue and nausea.
Weeks 1 to 4
Baby. Conception happens around week 2. The fertilised egg divides as it travels down the tube and implants in the uterine lining around the end of week 3 or the start of week 4.
You. You may feel nothing at all. Some women notice light spotting at implantation, mild cramps, breast tenderness or tiredness. A pregnancy test turns positive around the time your period is due.
To do. Start or continue folic acid. Book your first antenatal visit. Stop alcohol and smoking. Review medicines with your doctor.
Weeks 5 to 6
Baby. The heart begins to beat around week 6, and the neural tube (which becomes the brain and spine) forms. At this stage, the embryo is only a few millimetres long.
You. Morning sickness may start, breasts feel sore, you need to urinate more often, and you are exhausted.
Tests. An early ultrasound at 6 to 8 weeks confirms the location of the pregnancy, the gestational sac, the yolk sac and the heartbeat, and dates the pregnancy. It also rules out ectopic pregnancy.
Weeks 7 to 8
Baby. Arms and legs form as small buds, facial features begin to appear and the main organs develop rapidly. By the end of week 8, the embryo is about the size of a kidney bean.
You. Nausea can peak. Food aversions and strong smells are common. Mood swings are normal.
Tip. Eat small, frequent meals. Ginger, dry snacks in the morning and vitamin B6 (as advised by your doctor) may help. If you cannot keep fluids down, contact your doctor, because severe vomiting (hyperemesis) needs treatment.
Weeks 9 to 10
Baby. From week 9 the embryo is called a fetus. Fingers and toes separate, the heart has four chambers, and the baby starts to move, though you cannot feel it yet.
You. Your waist may thicken, your clothes feel tighter and your veins become more visible. Constipation and bloating are common.
Weeks 11 to 13
Baby. Organs are formed and now mature. The baby is about the size of a lime by week 12, and kidneys start working.
Tests. The NT scan (nuchal translucency) and double marker blood test between 11 weeks and 13 weeks 6 days screen for chromosomal conditions. Routine blood tests also include haemoglobin, blood group and Rh factor, blood sugar, thyroid, HIV, hepatitis B, syphilis, and a urine test.
You. Nausea often starts to ease towards the end of this trimester, and energy returns. The risk of miscarriage drops considerably after 12 weeks. Many couples choose to share the news around now.
Warning signs in the first trimester
Contact your doctor if you have:
- Heavy bleeding or bleeding with severe cramps
- Sharp pain on one side of the abdomen, especially with dizziness or shoulder pain (possible ectopic pregnancy)
- Persistent vomiting with inability to drink
- Fever, burning urination or foul-smelling discharge
Second trimester (weeks 14 to 27)
For many women, this is the most comfortable stretch of pregnancy. Nausea fades, energy improves and the bump begins to show.
Weeks 14 to 16
Baby. The baby grows quickly, develops facial expressions and can suck its thumb. Hair and nails form.
You. You may feel better, with a better appetite. Your skin may glow, or you may notice dark patches (melasma) or a dark line down your belly (linea nigra). Nosebleeds and stuffy nose are common.
Tests. If you missed the first trimester screening, the quad marker test is done between 15 and 20 weeks. Amniocentesis, if advised, can be done from about 15 weeks.
Weeks 17 to 20
Baby. The baby is about the length of a banana or around 25 cm at 20 weeks. Fine hair (lanugo) covers the skin, a protective coating (vernix) forms and the baby's movements become stronger.
You. You may feel the first movements ("quickening") between 16 and 22 weeks, sooner if it's not your first pregnancy. They feel like flutters or bubbles.
Tests. The TIFFA (anomaly) scan between 18 and 20 weeks checks the baby's structure in detail, the placenta and fluid. In India, the sex of the baby cannot be disclosed by law.
Vaccines. The tetanus (Td/Tdap) injection is given, with a second dose after a gap in some schedules. Your doctor will advise on influenza vaccine as well.
Weeks 21 to 24
Baby. The baby develops a sleep-wake pattern, hears sounds and responds to voices. By 24 weeks, the lungs are developing, and survival outside the womb becomes possible with intensive care, though preterm babies at this stage face major challenges.
You. Backache, round ligament pain (sharp pains on the sides of the belly when you move), leg cramps, heartburn and swollen ankles may appear. Stretch marks may develop.
Tip. Sleep on your side, use a pillow between the knees, wear comfortable footwear and walk daily. Moisturising the skin is fine, though it won't prevent stretch marks reliably.
Weeks 25 to 27
Baby. The baby gains weight and fat and may respond to touch. Kicks are stronger.
Tests. A glucose tolerance test (OGTT) for gestational diabetes is usually done between 24 and 28 weeks (earlier if you have risk factors). Haemoglobin is rechecked.
Common issues. Braxton Hicks contractions (irregular tightenings that are painless and settle with rest), heartburn, constipation and difficulty sleeping.
Warning signs in the second trimester
Contact your doctor if you have:
- Bleeding or leaking fluid
- Regular tightening or lower abdominal pain before 37 weeks
- Severe headache, blurred vision or sudden swelling of the face and hands
- Decreased or absent baby movements once established
- Severe itching, especially of the palms and soles
- Fever or painful urination
Third trimester (weeks 28 to 40+)
The final stretch brings a heavier body and more frequent visits as you and your baby prepare for birth.
Weeks 28 to 31
Baby. The baby opens its eyes, has regular sleep cycles and weighs around 1 kg at 28 weeks. The brain develops quickly.
You. You will notice breathlessness, back pain, swelling, more frequent urination and more vivid dreams. Piles and constipation are common.
Tests. Visits become every two weeks. Anti-D injection is given at about 28 weeks if you are Rh negative. A growth scan is often done around 28 to 32 weeks.
Kick counts. Start paying attention to the baby's movement pattern. A baby who is moving less than usual needs checking the same day.
Weeks 32 to 35
Baby. The baby gains weight rapidly and usually turns head-down. The lungs mature.
You. Braxton Hicks contractions increase, and you may feel tired and uncomfortable. Heartburn, swelling and sleeplessness are common.
To do. Enrol in antenatal classes, tour the delivery area, choose a paediatrician and pack your hospital bag. From about 34 to 35 weeks, perineal massage can be started if advised.
Weeks 36 to 37
Baby. The baby is about 2.5 to 3 kg and considered early term from 37 weeks. The head may drop into the pelvis ("lightening"), making breathing easier but pressure on the bladder worse.
Tests. Weekly visits begin. The doctor checks the baby's position, fluid and, if needed, performs a growth scan or Doppler study.
Weeks 38 to 40
Baby. The baby is fully developed, usually weighing between 2.8 and 3.5 kg.
You. You may notice more vaginal discharge, a mucus plug (a pinkish jelly) and stronger Braxton Hicks. Labour can begin at any time.
Know the signs of labour: regular painful contractions getting closer together, your water breaking, or bloody show with contractions. Go to hospital as your doctor advised.
Weeks 40 to 42
If you pass your due date, your doctor monitors you and the baby closely. Induction is usually offered between 41 and 42 weeks, earlier for medical reasons.
Warning signs in the third trimester
Seek help immediately if you have:
- Reduced fetal movements
- Heavy bleeding or constant severe abdominal pain
- Leaking fluid or rupture of membranes
- Severe headache, visual disturbance, upper abdominal pain or sudden swelling (possible preeclampsia)
- Fever
- Regular contractions before 37 weeks
Eating and activity through pregnancy
- Diet. Balanced meals with protein, grains, vegetables, fruit, dairy and healthy fats. Take iron, calcium, folic acid and vitamin D as prescribed. Limit caffeine, avoid raw or undercooked meat, fish with high mercury and unpasteurised dairy.
- Weight gain. Guided by your pre-pregnancy BMI. Average gain for a normal-weight woman is about 11 to 16 kg.
- Exercise. Walking, prenatal yoga and swimming are good for most women, unless your doctor advises otherwise.
- Sleep. Aim for 7 to 9 hours, sleeping on your side.
- Travel. Usually safe in the second trimester. Discuss long trips with your doctor.
- Sex. Safe in most uncomplicated pregnancies. Avoid it if advised, for example with placenta previa or bleeding.
- Medicines. Do not take any medicine or herbal product without checking.
- Mental health. Anxiety and low mood are common. Speak up if you struggle.
Antenatal visit schedule (typical)
- Up to 28 weeks: once a month
- 28 to 36 weeks: every two weeks
- 36 weeks until delivery: weekly
High-risk pregnancies need more frequent visits.
Questions mothers ask
When will I feel my baby move? Usually between 16 and 22 weeks.
Is it normal to have no morning sickness? Yes. Not everyone has it.
How much weight should I gain? It depends on your starting weight. Your doctor will guide you.
Can I travel by air? Usually safe until around 36 weeks if there are no complications, but check with your doctor and the airline.
When should I go to hospital? When you have regular contractions as your doctor advised, your waters break, you bleed or the baby is moving less.
Care you can rely on
Pregnancy is easier when you know what to expect and have a team to ask. I look after expectant mothers from Noida, Greater Noida, Ghaziabad and Delhi NCR at Prakash Hospital, Sector 33. To book a consultation, call +91 97023 46853.
Related reading
- Pregnancy scans and tests schedule
- Double marker test and NT scan
- TIFFA anomaly scan
- Gestational diabetes in pregnancy
- Normal delivery tips
This guide is general. Every pregnancy is different, and your doctor's advice about your own pregnancy always comes first.
