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Anatomy of pregnancy and birth

Key facts

  • You are pregnant from the moment of conception — and while you may not feel a change straight away, your body will begin to change immediately.
  • At the beginning of pregnancy, hormone changes can cause tiredness, nausea, vomiting, constipation and a need to urinate frequently.
  • As your baby and uterus grow, your abdominal muscles stretch and may become weaker.
  • As your body gets ready for childbirth, your cervix will start to soften and you may even lose your mucus plug.
  • During childbirth, you will feel uterine contractions that become more intense — they help your cervix fully dilate and your baby to move through your birth canal.

    • What happens during conception?

    Conception happens when an ovum (egg) is fertilised by a sperm.

    You are pregnant from the moment of conception. Pregnancy is measured in weeks, starting from the first day of your last period (Opens in new tab).

    Although you may not feel a change straight away, your body will begin to change immediately. Soon after you have conceived a baby, levels of a hormone called human chorionic gonadotropin (hCG) begin to rise.

    A higher level of hCG (Opens in new tab) can be used to confirm a pregnancy. It shows up in home pregnancy tests and blood tests organised by your doctor.

    What changes occur in early pregnancy?

    For many people, the first physical sign of pregnancy is a missed period (Opens in new tab). There are many other early signs of pregnancy.

    Hormonal changes

    Hormonal changes are essential in pregnancy and help ensure your baby's growth and development.

    Hormonal changes may also trigger:

    You may notice that your breasts become larger or feel sore or tender. Your nipples may also become darker. Not all people experience breast changes.

    Increased need to urinate

    You may notice an increased need to urinate (wee) in your pregnancy. This is caused by hormonal changes in early pregnancy.

    Later in pregnancy, as your uterus (womb) grows to accommodate your growing baby, there is more pressure on your bladder. This causes you to need to urinate (wee) more often.

    How will my body change over the course of my pregnancy?

    As your pregnancy progresses, more obvious physical changes occur, including the appearance of a 'baby bump'.

    Abdominal muscles

    Your abdomen changes shape during pregnancy as your baby grows and moves. Your abdominal muscles gradually stretch as your womb expands during pregnancy.

    Skin changes

    Hormonal changes may affect your skin. You may notice:

    • patches of darker skin called melasma on your face that will fade after your baby is born
    • you suddenly develop acne, or if you already have acne, it may get worse
    • stretch marks as you put on weight

    Weight gain

    During pregnancy, there are many different reasons why you will gain weight, such as:

    • your growing baby
    • amniotic fluid (the protective liquid within your uterus that surrounds your baby)
    • the increased size of your uterus
    • the placenta
    • additional breast tissue
    • increased blood volume
    • increased fat storage

    Gait (the way that you walk)

    Your gait can change as your pregnancy progresses. Your gait may change due to your:

    • centre of gravity changing with your growing uterus and weight gain
    • joints becoming more mobile
    • abdominal muscles weakening as your 'baby bump' increases in size

    How does my body prepare for childbirth?

    Physical changes happening during pregnancy also help prepare your body for birth.

    Pelvis

    Throughout your pregnancy, your pelvis changes.

    The pregnancy hormone relaxin makes the joints in your pelvis more mobile. This is to accommodate your growing baby and make it easier for your baby to travel through your birth canal.

    Uterus

    Throughout your pregnancy, your uterus occasionally tightens in preparation for labour. These 'practice contractions' are commonly referred to as Braxton Hicks contractions.

    Braxton Hicks contractions are irregular and usually they are not painful (but may be uncomfortable). They occur more often and feel stronger closer to your baby's due date.

    What are some of the changes in my body during childbirth?

    The cervix and the 'show'

    During your pregnancy, your cervix is long and closed. As childbirth approaches, your cervix starts to soften and dilate (open) to prepare for your baby going through your birth canal.

    As this happens, you may see a clear, pink, slightly bloody discharge or spotting (sometimes referred to as the 'show'). You may also notice the release of the white or yellow mucus plug that sits over the cervix during pregnancy. This is a signal that labour is approaching or has started.

    During labour, your cervix changes from long and firm to soft, thin and more elastic. It also dilates (opens). Changes to your cervix are partly triggered by contractions of your uterus, which help open the cervix.

    Diagram showing the female reproductive system.

    Illustration of the female reproductive system.

    The uterus

    During active labour, the muscles of your uterus contract to open your cervix and help your baby move down into the birth canal.

    Each contraction may start like a wave and build in intensity. You may feel your contraction moving from the top of your uterus right down to your cervix. During a contraction, your uterus will feel tight. Between contractions, the pain intensity may ease off and allow you to rest before the next one builds.

    Read more about what happens to your body in childbirth.

    Resources and support

    Looking for information for Aboriginal and/or Torres Strait Islander people?

    Looking for information for sexually and gender-diverse families?

    Speak to a maternal child health nurse

    Call Pregnancy, Birth and Baby to speak to a maternal child health nurse on 1800 882 436 (Opens in new tab) or video call. Available 7am to midnight (AET), 7 days a week.

    Last reviewed: November 2024

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