Need to talk? Call 1800 882 436.
It's a free call with a maternal child health nurse. *call charges may apply from your mobile

Is it an emergency? Dial 000
If you need urgent medical help, call triple zero immediately.

beginning of content

Anatomy of pregnancy and birth

4-minute read

From the moment you find out that you (or your partner) are pregnant you may be filled with a rush of emotions. In addition, there is a range of physical changes that many pregnant women go through. Learn about the anatomical changes you can expect throughout conception, pregnancy and childbirth.

What happens during conception?

Conception occurs when a woman’s ovum (egg) is fertilised by a male’s sperm. All of the baby’s genetic characteristics are decided in that instant. A woman is pregnant from the moment of conception, but pregnancy is measured in weeks – starting from the first day of the mother’s last menstrual period.

Although you may not feel a change straight away, your body will begin to change immediately. For example, levels of a hormone called human chorionic gonadotropin (hCG) will begin to rise very soon after conception. An elevated level of hCG will help confirm a pregnancy, and it shows up in either using a home pregnancy test or with a blood test done by a doctor.

Read more about the early signs of pregnancy here.

What physical changes occur in early pregnancy?

For many women, the first physical sign of pregnancy is a missed period. But there are many other changes happening to the mother's body in the early months:

  • Hormonal changes: hormonal changes are essential in pregnancy and help ensure your baby's growth and development. Hormonal changes may, however, also trigger nausea or vomiting (commonly referred to as 'morning sickness'), changes in the look or feel of the breasts, or feelings of tiredness or moodiness.

  • Changes to your breasts: not all women experience breast changes, but you might notice your breasts get larger, feel sore or tender, or your nipples might become darker.

  • Increased need to urinate: early in pregnancy, the amount of blood in the mother's body increases. This causes the mother's kidneys to process more fluid, resulting in an increased need to urinate. As the womb (uterus) grows to accommodate the growing baby, there is also more pressure on the bladder, leading to a need to urinate more often.

  • Some weight gain: with fuller breasts, a growing uterus and increased blood volume, a small amount of weight gain is to be expected. A pregnant woman may gain 1 to 2 kilograms in her first trimester.

  • Changes to the cervix: the cervix is a muscular cylinder at the bottom of the uterus. From conception until late in pregnancy (just before birth), the cervix protects the growing baby by increasing in size and strength.

How does your body change over the course of the pregnancy?

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

  • Abdominal muscles: the mother's abdomen constantly changes shape during the pregnancy as the baby grows and moves. The abdominal muscles gradually stretch as the womb expands during pregnancy.

  • Skin changes: hormonal changes may affect the skin. For example, a pregnant woman may get acne, or existing acne may worsen. Some women notice patches of darker skin on the face (called chloasma); these will fade after the baby is born. Stretch marks may also appear, particularly if there is weight gain.

  • Weight gain: further weight gain is caused mainly by the growing baby, increased amounts of amniotic fluid (the protective liquid within the uterus that surrounds the baby), and the increased size of the uterus and placenta.

How does your body prepare for childbirth?

Physical changes in the third trimester help prepare a woman's body for birth.

  • Pelvis: the pelvis of a pregnant woman changes throughout pregnancy, including changes to its shape, how it sits within the body, and how the joints and ligaments behave. The joints and ligaments of the pelvis relax during pregnancy to accommodate the growing baby. As the due date approaches, the pelvis expands to create space for the baby travel through the birth canal during birth.

  • Uterus: the muscles of the uterus may occasionally tighten in preparation for labour, which are commonly referred to as Braxton Hicks contractions. These 'false' or practice contractions are irregular, not usually painful (but may be uncomfortable) and tend to occur more often and feel stronger closer to the baby's due date.

  • The 'show': the cervix may softens and dilates (opens) to prepare for the baby's passage through the birth canal. As the cervix opens, the vagina might release a clear, pink, or slightly bloody discharge (sometimes referred to as the 'show'). This is the release of the mucous plug that sits over the cervix during pregnancy, and may signal that labour is approaching.

  • During active labour, the muscles of the uterus contract purposefully, to help the baby move down into the birth canal. Each labour contraction may start like a wave and build in intensity, moving from the top of the uterus right down to the cervix. Your uterus will feel tight during the contraction. But between contractions, the pain may ease off and allow you to rest before the next one builds.

Read more about what happens to your body during child birth.

Learn more here about the development and quality assurance of healthdirect content.

Last reviewed: October 2020

Back To Top

Need more information?

Premature birth & premature babies | Raising Children Network

This essential guide for parents of premature babies covers gestational age, premature birth risk factors, premature labour and premature development.

Read more on website

Preterm labour -

Going into labour before your 37th week of pregnancy is called preterm labour, or premature labour.

Read more on myDr website

How much weight will I gain during pregnancy? | Queensland Health

Find out how much weight you should expect to gain at each stage of pregnancy, based on your BMI, and tips on what to eat and how to exercise while pregnant.

Read more on Queensland Health website

RANZCOG - Labour and Birth

Every labour and birth is unique and unpredictable, making it difficult to plan. It is common for women to feel some level of anxiety during pregnancy; perhaps about their changing body, the health of their baby or concerns about the birth.

Read more on RANZCOG - Royal Australian and New Zealand College of Obstetricians and Gynaecologists website

Induction of labour

Inducing labour allows women to deliver their baby normally by stimulating labour contractions. There are several medical and surgical techniques which can be used.

Read more on Parenthub website

Induced labour

Induced labour is a medical treatment to start labour. It may be recommended if your baby needs to be born before labour is due to start naturally.

Read more on Pregnancy, Birth & Baby website

Induced labour – what are the options?

Induced labour can be started in several ways. Your doctor will discuss with you what your options are as well as any possible risks to you or your baby.

Read more on Pregnancy, Birth & Baby website

Stretch and sweep

A stretch and sweep or membrane sweep is a relatively gentle way of trying to start labour.

Read more on Pregnancy, Birth & Baby website

What happens to your body in childbirth

During childbirth, the body’s hormones and muscles, as well as the shape of the pelvis, all work together to bring the baby safely into the world.

Read more on Pregnancy, Birth & Baby website

RANZCOG - Pain Relief in Labour and Childbirth

Every woman experiences pain in a different way. The way you experience pain depends on your emotional, psychological, social, motivational and cultural circumstances. Every woman responds and copes differently with the pain of labour and childbirth.

Read more on RANZCOG - Royal Australian and New Zealand College of Obstetricians and Gynaecologists website

Call us and speak to a Maternal Child Health Nurse for personal advice and guidance.

Need further advice or guidance from our maternal child health nurses?

This information is for your general information and use only and is not intended to be used as medical advice and should not be used to diagnose, treat, cure or prevent any medical condition, nor should it be used for therapeutic purposes.

The information is not a substitute for independent professional advice and should not be used as an alternative to professional health care. If you have a particular medical problem, please consult a healthcare professional.

Except as permitted under the Copyright Act 1968, this publication or any part of it may not be reproduced, altered, adapted, stored and/or distributed in any form or by any means without the prior written permission of Healthdirect Australia.