Third Trimester


Once you reach the third trimester of pregnancy, you’re well over half way there. As you look forward to the birth of your baby, there is plenty to plan for and decisions to make. You might find you’re slowing down, or you might be filled with energy to clean, tidy and organise as you prepare for your baby’s arrival. This urge to clean is known as the ‘nesting’ instinct.

What is the third trimester?

Pregnancy is defined in three-month blocks of and third trimesters. Reaching of your pregnancy means that you’re now in the third and final trimester. Officially, this trimester continues to , but in reality, the trimester will end whenever your baby is born.

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 is considered to have been born full-term if it is born in weeks 37 to 42 of pregnancy. A baby born before week 37 is considered premature, and if your baby has not been born by week 42, labour may be induced.

What happens to your body?

As you get closer to the time your baby will be born, here are some things you’ll notice:

  • Your skin and ligaments continue to stretch to accommodate your growing baby.
  • You get tired easily, and sleeping becomes more difficult.
  • You experience heartburn and/or breathlessness, as the baby grows in your abdomen.

While these are all part of a normal pregnancy, you can take steps to minimise discomfort. Speak with your doctor or midwife for suggestions, particularly if you are in pain.

You may also experience Braxton-Hicks contractions, which are a tightening of the muscles of the uterus. They 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 has engaged or dropped’. You will notice more room near your ribs and breathing will become 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 begins to prepare for the coming labour. The cervix begins to soften, and many women 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 your labour will soon begin.

What happens to the baby?

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 one in 25 of all babies will be in the ‘breech position’, rather than the usual head-down position, at the start of labour. If this is your situation, 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.