Pregnancy Week-by-Week Guide
See how your baby is growing and what to expect each week of pregnancy.
Pregnancy Week-by-Week Guide
Enter your due date to see personalized weekly development updates
Quick answer
Pregnancy lasts about 40 weeks counted from the first day of your last period, split into three trimesters: weeks 1–13, 14–27 and 28–40. Your baby's organs form in the first trimester, you usually feel movements by 16–22 weeks, and babies are considered full term at 39–40 weeks.
How pregnancy weeks are counted
Pregnancy weeks are counted from the first day of your last menstrual period, not from conception. That means you are already about two weeks 'pregnant' when you conceive, and four weeks when a pregnancy test turns positive.
Choose a week to see your baby's approximate size and development, common symptoms and tips for that stage. Sizes are averages; babies vary.
Milestones through pregnancy
Approximate timings; your care team will tell you what applies to you.
| Week | What's happening |
|---|---|
| 4–5 | Pregnancy test turns positive; neural tube starts forming |
| 6–8 | Heartbeat may be seen on an early scan |
| 11–14 | First-trimester (nuchal) scan and dating scan |
| 16–22 | Most parents feel the first movements |
| 18–22 | Detailed anatomy (anomaly) scan |
| 24–28 | Glucose test for gestational diabetes |
| 28 | Third trimester begins; track your baby's movements |
| 37 | Early term |
| 39–40 | Full term — your estimated due date |
Frequently asked questions
When does the second trimester start?
At week 14. The first trimester is weeks 1–13 and the third starts at week 28.
When will I feel my baby move?
Usually between 16 and 22 weeks — earlier in second and later pregnancies, later in a first pregnancy.
How big is my baby at 20 weeks?
Around 25 cm from head to heel and about 300 grams, roughly the length of a banana.
Why am I '4 weeks pregnant' when I only just conceived?
Weeks are counted from your last period, about two weeks before conception.
Call your doctor or maternity unit if you have
- Bleeding, fluid leaking or severe tummy pain
- Reduced or changed baby movements after 24–28 weeks
- Severe headache, vision problems or sudden swelling
- Fever, or severe vomiting that stops you keeping fluids down
In an emergency call 112 (India) or 911 (US). This tool gives general information, not medical advice.
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