Key summary
- The first trimester of pregnancy begins on the first day of your last period and lasts until the end of week 12.
- Common pregnancy symptoms include morning sickness, tiredness, sore breasts and a heightened sense of smell.
- Experts recommend not drinking alcohol or smoking and reducing your caffeine intake. It’s also best to reduce your risk of listeria by avoiding sushi, soft cheeses and soft-serve ice-cream.
- During this trimester you should see your GP to confirm your pregnancy and work out the next steps for your care.
Congratulations! You’re pregnant. If you’ve just found out you’re expecting, the first trimester can bring on a mix of emotions as your body adjusts to the changes. Understanding first trimester essentials and the danger signs of pregnancy in the first trimester can help you feel more confident as you start your parenting journey.
What are first trimester symptoms?
Morning sickness
Morning sickness is one of the most common symptoms of the first trimester, affecting half of pregnant women – and despite the name, it can strike at any time of day or night. You may experience nausea, vomiting, loss of appetite and sickness that can be triggered by certain foods and smells.
Extreme tiredness
Extreme tiredness is very common, explains obstetrician and gynaecologist Associate Professor Gino Pecoraro. "It's normal to feel exhausted. Your heart, lungs and kidneys are working 60 per cent harder from the start of pregnancy," he says.
Hormonal changes
Hormonal changes may cause your breasts to feel sensitive or sore and you may need to wee more often than usual. Some women experience a metallic taste, while others notice a stronger sense of smell.
Food cravings and aversions
Cravings for certain foods are common first trimester symptoms, especially for energy and calcium-rich foods like milk and other dairy foods. You may also develop aversions to foods you previously enjoyed.
Weight changes
During the first trimester, expect to gain around one to two kilos – or less if you have morning sickness affecting your appetite and food intake.
Mild or no symptoms
Although pregnancy symptoms are typical during the first trimester, you might not experience any symptoms or they may be mild. This is completely normal and doesn't indicate any problems with your pregnancy.
How is my baby changing in the first trimester?
The first trimester is an exciting time, as your baby rapidly transforms from a tiny fertilised egg into a developing foetus. Here's a brief snapshot of key developmental milestones:
Week 1-4
During these early weeks, fertilisation occurs and the embryo implants into the uterine wall. The very basic foundation of your baby begins to form, though it's still incredibly tiny - smaller than a grain of rice by week 4.
Week 5-8
This is when the magic really starts happening. Your baby's heart begins to beat around week 6, and basic structures like the brain, stomach, and intestines start forming. Small bumps called 'limb buds' appear where arms and legs will eventually grow, and facial features begin to develop.
Week 9-12
Your embryo officially becomes a foetus during this period and reaches approximately 6cm in length by week 12. Major organs continue developing and becoming more sophisticated, while tiny fingers and toes start to form. By the end of this trimester, your baby looks recognizably human.
Remember, every pregnancy is unique, and development can vary slightly. Regular antenatal checks help monitor your baby's growth closely.
Tips on getting through the first trimester
The first 12 weeks of pregnancy can be a wild ride. Here are some ideas to help you get through it.
Learn what to avoid during the first trimester
When it comes to diet and lifestyle during pregnancy, experts recommend not drinking alcohol or smoking and reducing your caffeine intake. It's also best to reduce your risk of listeria by steering clear of common culprits like sushi, soft cheeses and soft-serve ice-cream.
Foods to enjoy
You may have to quit some of your favourite foods for the next nine months, but there are many other foods that are helpful to eat during pregnancy. Eating a balanced diet helps support your pregnancy health:
- Fruits and vegetables
- Wholegrain breads and cereals
- Low-fat dairy products
- Lean meats, fish, lentils, and legumes
- Daily folic acid supplement (recommended up to three months after conception)
Managing morning sickness
Try eating small, frequent meals throughout the day rather than three large ones. Ginger can help settle your stomach. Try ginger tea or ginger biscuits. Keep plain crackers by your bedside to nibble before getting up and avoid foods or smells that trigger your nausea.
Staying hydrated
Drink plenty of water throughout the day, especially if you're experiencing morning sickness. If plain water feels unappealing, try adding lemon or lime, or sipping herbal teas. Small, frequent sips often work better than large amounts at once.
Exercise regularly
Gentle, regular exercise can help with energy levels and mood during pregnancy. Walking, swimming, and prenatal yoga are excellent options. Always check with your healthcare provider before starting any new exercise routine during pregnancy.
When should I see my doctor?
See your GP early to:
- Confirm your pregnancy
- Plan your antenatal care pathway
- Discuss whether you'd prefer midwife, obstetrician, or shared care
- Choose between public or private hospital options
Contact your healthcare provider if you experience:
- Unusual pain or bleeding
- Severe nausea or vomiting
- Any physical or mental health concerns
- Worries about your pregnancy
Remember: "A big part of what we do in medicine is to allay fear," says Assoc Prof Pecoraro. "If you've got concerns and you've never done this before, you won't have all the answers. I'd much rather you came to see me, your GP, or your midwife so we can address your concerns. That's what we're here for."
Looking ahead: The first trimester is a time of significant growth and change. Maintaining a healthy lifestyle, staying hydrated, and seeking support from healthcare professionals will help you navigate this period as you progress toward the second and third trimesters.