Forty weeks can feel like a very long, very unknown road. Splitting it into three trimesters makes it easier to picture — each one is its own chapter, with its own feelings, changes, and checkups. Here is a calm walk through all three.
This article is for general information only and isn’t medical advice — your doctor or midwife is the best person to ask about your own pregnancy.
How many weeks is each trimester?
Pregnancy is measured in weeks, counted from the first day of your last period — which is why the first couple of weeks technically happen before you conceive. The three trimesters break down like this:
| Trimester | Weeks | Roughly |
|---|---|---|
| First | 1–13 | The first ~3 months |
| Second | 14–27 | The middle months |
| Third | 28–40+ | The last stretch to birth |
A full-term pregnancy is usually around 40 weeks, though anywhere from 37 to 42 weeks is considered normal. You may also hear pregnancy described in months — but weeks are more precise, because the months don’t divide evenly into the trimesters. That’s why almost all checkups, scans and milestones are tracked by week, not by month. If you ever lose track of where you are, our pregnancy week tracker tells you your current week, trimester, and roughly how far along you are from your due date.
What happens in the first trimester (weeks 1–13)?
This is the busiest, most invisible chapter — enormous things are happening while you may not look pregnant at all.
- For your baby: From a cluster of cells, your baby grows a beating heart, a brain, and the beginnings of arms, legs, eyes and ears. By the end, all the major organs have started forming.
- For you: Hormones surge. Many people feel tired, queasy (“morning” sickness can strike any time of day), tender, and emotional. Some feel almost nothing — and that is completely normal too.
- Key checkups: A first (“booking”) visit to confirm the pregnancy and talk through your history, often a dating scan, and early blood tests. Some screening tests are offered in this window.
Be kind to yourself here. The tiredness is real, and it usually eases as the next trimester begins. Eating little and often, sipping water, and resting when you can all help — and there is no prize for pushing through. If something worries you, a quick call to your provider is always reasonable.
What happens in the second trimester (weeks 14–27)?
Many people call this the “honeymoon” stretch — and for good reason.
- For your baby: Your baby grows quickly, starts to move, and develops fingerprints, hair and the ability to hear. Around the middle of this trimester, an anatomy scan checks how your baby is developing.
- For you: Early nausea and fatigue often fade. Your bump starts to show, and somewhere in here you may feel the first flutters of movement (often called “quickening”). Energy frequently returns.
- Key checkups: The mid-pregnancy anatomy scan (often around weeks 18–22), routine checks of your blood pressure and growth, and — later in this trimester — screening for gestational diabetes in many places.
This is often a good window for the more practical, less urgent tasks: planning leave, thinking about a birth setting, and starting a loose list of baby basics. With your energy back, it’s a natural time to read up, ask questions at appointments, and picture the months ahead — without the pressure of a deadline.
What happens in the third trimester (weeks 28–40+)?
The final chapter — getting bigger, getting ready, and getting closer.
- For your baby: Your baby puts on weight, builds up fat, and practises breathing movements. The brain develops rapidly. Toward the end, most babies settle into a head-down position ready for birth.
- For you: Comfort can get harder. Common, normal experiences include backache, heartburn, swollen feet, trouble sleeping, and Braxton Hicks — practice tightenings that aren’t true labour.
- Key checkups: Appointments become more frequent — often every couple of weeks, then weekly near the end. Your provider checks your baby’s position, growth, your blood pressure, and talks through your birth plan.
If you start noticing tightenings, it helps to know the difference between practice contractions and the real thing — our guide on Braxton Hicks vs real contractions breaks it down.
What stays the same across all three?
A few threads run through the whole journey:
- Regular checkups are the backbone — they catch issues early and reassure you between the big moments.
- Rest, food and water matter in every trimester, even when the symptoms change.
- Your feelings are valid — excitement, worry, boredom and impatience can all show up, sometimes in the same afternoon.
- Every pregnancy is different, so try not to measure yours against anyone else’s timeline or symptoms. The ranges here are typical, not rules.
Knowing which chapter you’re in makes the whole thing feel less like an endless wait and more like a journey with clear stages. Keep an eye on your week with the pregnancy week tracker, and take each trimester as it comes.
This article is for general information only and isn’t medical advice. Your healthcare provider is the best person to ask about your own pregnancy and the right schedule of care for you.