Trimester 1

First trimester: weeks 1–13

The first three months are about confirming care, protecting early development, managing symptoms and understanding your first tests.

In 60 seconds

What to know now

  • Common examples include fatigue, nausea, breast tenderness, food aversions, frequent urination, constipation and rapidly changing emotions. Some people have very few symptoms.
  • From implantation through the early fetal stage, the foundations of organs, limbs, brain and spinal cord form. Week labels are approximate because dating can change after assessment.
  • Arrange prenatal care and learn the urgent contact route.

What you may notice

Your body and how you may feel

Common examples include fatigue, nausea, breast tenderness, food aversions, frequent urination, constipation and rapidly changing emotions. Some people have very few symptoms.

Symptoms that interrupt drinking, severe or one-sided pain, fainting, heavy bleeding or a feeling that something is seriously wrong should not wait for a routine visit.

What is happening

Baby’s development this week

From implantation through the early fetal stage, the foundations of organs, limbs, brain and spinal cord form. Week labels are approximate because dating can change after assessment.

Plain-language examples

What this means in real life

What 'three months' means here: weeks 1–4 are month 1, weeks 5–8 month 2, and weeks 9–13 month 3. Care teams still use weeks for decisions.

A short checklist

What to do now

  • Arrange prenatal care and learn the urgent contact route.
  • Review medicines and supplements with a clinician or pharmacist.
  • Choose food-safety and substance-free habits without chasing perfection.

Pause and check

What not to do—or what to ask first

  • Avoid alcohol, smoking and recreational drugs; check medicines, supplements and higher-risk foods instead of relying on a social-media safe/unsafe list.
  • Ask when a recommendation depends on your history, symptoms or pregnancy.
Check food, medicines, exercise and everyday activities →

What may be coming up

Appointments, tests and decisions

Typical early care may include booking history, blood and urine tests, dating assessment and optional screening. The exact order and timing depend on location and history.

For the support person

One useful thing a partner can do

  • Take on calls, food experiments and household work; treat exhaustion and nausea as real even before pregnancy is visible.

Contact your care team

Contact your doctor or maternity team promptly

Some concerns need advice before the next routine appointment even when they do not feel like an emergency. If a symptom becomes severe, sudden or frightening, use urgent care instead.

See when to contact care

Urgent or emergency

Urgent signs during pregnancy or within a year after birth

Get medical care immediately for these symptoms. The list is not exhaustive; if something feels seriously wrong, seek help.

Open urgent warning signs