What is the third trimester?

Pregnancy is divided into 3 blocks of 3 months each the first, second and third trimesters. Reaching week 27 of your pregnancy means you're now in the third and final trimester. While this trimester could end at week 40, in reality it ends whenever your baby is born.

A baby born in weeks 37 to 42 of pregnancy is considered to be full-term'. Babies born before week 37 are considered premature.

If your baby has not been born by week 42, your doctor or midwife may recommend induction of labour to reduce the chance of complications.

What happens to my body in the third trimester?

As you get closer to your baby's birth, here are some things you may notice:

• Your skin and ligaments continue to stretch to make room your growing baby.
• You get tired more easily, and sleeping becomes more difficult.
• You experience heartburn and/or breathlessness, as the baby grows larger and puts more pressure on your organs, such as your lungs.

While these are all part of a normal pregnancy, there are thing you can do to minimise any discomfort. Speak with your doctor or midwife for suggestions, especially if you are in pain.

You may also experience Braxton-Hicks contractions. These are a tightening of the muscles of the uterus that last around 30 seconds, are irregular and not painful. They are not labour contractions, and not a sign that labour has begun.

If this is your first baby, you may notice around 36 weeks that your baby has moved further down into your pelvis. This is often referred to as the baby engaging' or dropping' in the pelvis. You may notice more room near your ribs, making breathing easier, but this also adds more pressure on your bladder (meaning more trips to the toilet).

In the last few weeks of this trimester, your body may begin to prepare for the coming labour. The cervix will start to soften, and you may notice a show'. The show' is the release of the mucous plug that sits within the cervical canal during pregnancy and is an early sign that labour will soon begin.

What happens to my emotions in the third trimester?

During this last stage of pregnancy, you may be worried or anxious about labour and birth, or about how you will manage as a parent.

It can be difficult to get comfortable in bed, and you will have more frequent bathroom visits. This can mean poor sleep, which can also trigger irritability and low mood.

While it's common to see the third trimester as an exciting time and feel positive about the next stage, 1 in 5 people will experience antenatal anxiety or depression. Seek help early if this is how you (or your partner) are feeling.

What happens to my baby in the third trimester?

By week 31, your baby's lungs are more mature, but are yet to produce surfactant, a substance that helps with breathing once they are born.

By week 36, your baby is about 47cm long and weighs approximately 2.6kg. Your baby's head may start to engage or sit lower into your pelvis at this time, getting ready for labour. Around 1 in 25 of all babies will be in the breech position (bottom first), rather than the usual head-down position, at the start of labour.

If your baby is breech, your doctor or midwife will discuss with you what this means for your labour, what your options are and how your baby might be born.

By 40 weeks, your baby will be about 50cm, and weigh approximately 3.4kg.

Developmentally, your baby is now ready to be born.

What can I expect from my doctor or midwife?

Through the third trimester you will have more frequent antenatal check-ups: about every 4 weeks until 36 weeks, then every 2 weeks after that your health team will set your appointment schedule.

If you haven't already had them, you may also be offered:

• a blood test for gestational diabetes
• a test for group B strep (streptococcal)
• whooping cough (pertussis) vaccination
• flu (influenza) vaccination

How can I stay healthy through the third trimester?

To give your baby a healthy start, it's important to eat healthy foods throughout pregnancy. Ensure your diet is varied and includes a range of fresh fruit and vegetables as well as sources of protein, iron and calcium. Don't forget to drink plenty of water too.

Weight gain is a normal part of pregnancy. Most people can expect to gain between 11 and 16kg.

A pregnancy weight gain calculator can be a handy tool to track your weight gain through the third trimester.

Try to stay active throughout pregnancy even in your third trimester. While it's important to stick with safe, gentle exercise as you get closer to your due date, it's a good idea to continue to participate in regular exercise as part of a healthy lifestyle.

When should I seek medical help?

Contact your doctor, midwife or hospital immediately if you experience any of the following symptoms:

• vaginal bleeding or constant, clear watery vaginal discharge
• severe nausea, vomiting or abdominal pain
• sudden blurry vision or a severe headache
• sudden swelling of the face, fingers or ankles
• fever
• regular, painful contractions before 37 weeks of pregnancy
• a change in your baby's movements

What are signs of labour?

Every labour is different and can start in different ways. Here are some signs you may notice:

• Your waters break.
• You are having regular, painful contractions.
• You may have nausea, vomiting, soft stools or diarrhea.
• Your mucous plug may come away.

If you think your labour has started, it is a good idea to call your hospital, midwife or doctor to let them know.

What else should I consider in the third trimester?

As you enter the third trimester it's a good idea to:

• Pack a hospital bag.
• Book a hospital/birthing centre tour.
• Arrange a properly fitted car seat to bring your baby home.
• Consider what you will need when you bring your baby home what will you buy, and what can you borrow from family or friends?
• If you have other children (or pets), plan for their care while you are in hospital.
• Consider shopping ahead especially for non-perishable staples (such as tinned food and bathroom products).
• Considering cooking double portions through your third trimester and loading your freezer for when things get busy after your baby is born.

Resources and support

Follow your pregnancy week-by-week to find out how your baby is growing and what is happening to your body.

For more information about the third trimester of pregnancy and what to expect during your baby's birth, see the following websites:

• The 'Having a baby' book by the New South Wales Department of Health has important health information.
• The Royal Women's Hospital website has resources and factsheets.
• What to expect during pregnancy' by Queensland Department of Health is a great resource throughout pregnancy.