The first trimester, from conception through to about 12 weeks, is a time of incredible change. Understanding what to expect physically, emotionally and medically during these early weeks can help you feel more confident and supported. This guide covers common symptoms, important antenatal checks, lifestyle tips, and red flags so you know when to reach out for extra care.
Understanding the First Trimester (Weeks 1-12)
What defines the first trimester
- The first trimester begins from the first day of your last menstrual period, up to around 12 weeks gestation.
- It’s when many of the major developments in the embryo and foetus begin: organs forming, heartbeat, and limb buds.
Baby’s growth week-by-week highlights
- By the end of week 12, the foetus is more recognisable with limbs, facial features and early organ systems.
- A first ultrasound is often done around 10-12 weeks to help determine due date, check for multiples and assess development.
Common Physical & Emotional Changes
Physical symptoms you may experience
Symptom | What to expect | Approximate timing |
Missed period | Often the first sign. Confirm with a test or GP visit. | Around week 4-5 |
Nausea & vomiting (“morning sickness”) | Can happen any time of day; ranges from mild queasiness to more severe. | Often starts around weeks 5-6 and may ease by week 12 |
Breast changes | Tenderness, swelling, darker areolas, noticeable veins. | Early weeks, often from weeks 4-6 |
Fatigue (tiredness) | Hormonal changes and increased metabolic demands contribute. | Often noticeable from week 4 onward |
Frequent urination | Growing uterus and hormonal shifts place pressure on the bladder. | Early, increasing later in first trimester |
Food cravings / aversions, metallic taste, smell sensitivities | Hormonal changes can alter taste and smell. | Any time during early pregnancy |
Emotional & mental health changes
- Mood swings, anxiety or worry are common. Adjusting to the idea of being pregnant can feel overwhelming.
- Many women also feel happiness, relief and excitement – often mixed with uncertainty.
- Sleep changes are frequent, such as vivid dreams or waking often.
Medical Care & Screening in the First Trimester
Your first antenatal appointment
- Best practice is to have your first antenatal visit within the first 10 weeks of pregnancy.
- At this visit, your provider (GP, obstetrician or midwife) will confirm the pregnancy, estimate your due date, review your medical history and check for risk factors.
Tests and screenings
- Blood tests: full blood count, blood type, antibody checks and screenings for infectious diseases.
- Genetic screening: options such as combined first trimester screening or non-invasive prenatal testing.
- Ultrasound scan around 10-12 weeks for dating, viability and identifying multiples.
How to Support a Healthy First Trimester
Nutrition, supplements & habits
- Folic acid is critical in preventing neural tube defects.
- Iodine is also important, alongside a balanced diet with plenty of fruit, vegetables, lean protein, whole grains and dairy or alternatives.
- Stay hydrated and eat small, frequent meals if nausea is strong.
- Avoid alcohol, stop smoking, limit caffeine and discuss medications with your care provider.
Physical activity & rest
- Gentle exercise is generally beneficial, such as walking, yoga or swimming.
- Fatigue is common, so rest when needed and adjust your schedule if possible.
What to avoid
- Alcohol, smoking and illicit substances.
- Some foods such as raw or undercooked meats, certain seafood and unpasteurised dairy.
- Heavy lifting, exposure to harmful chemicals or overheating environments.
When to Seek Medical Advice (Red Flags)
You should contact your GP, obstetrician or midwife immediately if you experience any of the following:
- Vaginal bleeding or spotting, especially if heavy or accompanied by pain.
- Severe abdominal pain or cramping.
- Severe or persistent nausea and vomiting (unable to keep fluids down).
- Fainting, dizziness, fever, or signs of infection.
- If you have a history of complications or other risk factors that cause concern.
Your Role & What You Can Do
- Keep open communication with your healthcare provider.
- Track symptoms and ask questions about tests, diet, or medication.
- Build a support network with your partner, family or friends.
- Begin adjusting work, rest and routines to support your pregnancy journey.
At Sirona Women’s Health, our team provides comprehensive care throughout pregnancy, including antenatal appointments, monitoring and support. For more details, see our Pregnancy services page. To learn more about our team and how we support women through all stages of life, visit our homepage.
Disclaimer:
The information provided in this blog is for general educational purposes only and should not be taken as medical advice. It is not a substitute for professional diagnosis, treatment, or care. Always seek the guidance of your doctor or other qualified healthcare professional with any questions you may have regarding your health or medical condition.