Pregnancy is usually described in three stages: the first, second and third trimesters. Each brings changes, but there is no single timetable for how you should feel. This overview explains the broad pattern and the care to discuss along the way.
How pregnancy weeks are counted
Pregnancy is usually dated from the first day of your last menstrual period, with an estimated due date around 40 weeks later. This starts the count before conception in a typical cycle. Your maternity team may use an ultrasound to help establish the date, especially if your periods are irregular or the dates are uncertain.
Trimester boundaries differ slightly between resources. Here, early pregnancy means roughly the first 12 to 13 weeks, the middle stage runs until about 27 weeks, and the third trimester begins at about 28 weeks. Your exact gestational age in weeks and days matters more than the label when arranging tests or making care decisions.
First trimester: early development and starting care
Early pregnancy is a time when the foundations of the brain, spinal cord, heart and other organs are developing. Formation and maturation continue over time; an organ beginning to form does not mean it is ready to function independently.
You may notice nausea, tiredness, breast tenderness or needing to wee more often. Others have few symptoms. Symptoms can change from day to day and cannot confirm whether a pregnancy is developing normally. Seek help for symptoms that prevent you eating, drinking or managing daily life rather than assuming you must put up with them.
Arrange antenatal care with a GP or midwife early. Discuss your health history, medicines, supplements, mental wellbeing and support needs. The team can explain blood and urine tests, ultrasound and screening choices, including what each can and cannot tell you. Some choices have time windows, so raise questions at the first appointment.
Second trimester: growth and new sensations
Your baby continues to grow and their organs keep developing. Some people find nausea or fatigue eases; others still need treatment or more rest. Back or pelvic discomfort, constipation and heartburn can occur, but a new, severe or persistent symptom still deserves assessment.
Many people first notice movements between about 16 and 24 weeks. Early sensations may be subtle. If you have not felt movement by 24 weeks, tell your midwife or doctor. Once you are familiar with your baby’s movements, contact the maternity service immediately if they become less, stop or change in a way that worries you.
A detailed ultrasound is commonly offered around 18 to 22 weeks to assess the baby’s anatomy and other features of the pregnancy. It cannot identify every condition or guarantee a healthy outcome. Your team will also discuss testing for gestational diabetes, usually at 24 to 28 weeks, with earlier assessment for some people.
Third trimester: ongoing development and preparing for birth
Growth and organ maturation continue, including in the brain and lungs. How big your bump looks, or how uncomfortable you feel, cannot tell you exactly when your baby will be ready to be born.
Sleep may be interrupted and you may need to change positions more often. From 28 weeks, settle to sleep on either side, including for naps. If you wake on your back, turn onto your side and return to sleep.
Keep your scheduled appointments. Discuss recommended vaccinations, your baby’s position, birth preferences, pain relief, feeding support and where to call when labour starts. Tests and additional scans depend on your circumstances and local care pathway.
Your baby should keep moving as birth approaches and during labour. Do not explain reduced movement as simply running out of room, and do not use a home Doppler to decide that everything is fine. Seek assessment without waiting until tomorrow.
Your due date is an estimate
Birth may happen before or after the estimated date. Ask your team before the due date about the plan if pregnancy continues, including the benefits, risks and timing of induction or ongoing monitoring. Do not wait until a particular week to seek care if you are worried.
Get help for warning signs at any stage
Contact your maternity service or doctor immediately for bleeding, severe abdominal pain, leaking fluid, fever, severe headache or vision changes, or concerns about movements. Possible labour before 37 weeks also needs urgent assessment. In early pregnancy, one-sided pelvic pain or shoulder-tip pain, especially with bleeding or dizziness, needs urgent medical assessment.
In Australia, call 000 for heavy bleeding, collapse, severe breathing difficulty or a seizure. If you cannot reach your maternity team promptly for an urgent concern, go to an emergency department. A calendar or symptom checklist cannot replace assessment.
This is general information for Australian readers. Your own care plan may include different appointments or tests.
Related reading
Our labour and birth guide explains signs, stages and when to contact your maternity team.