Pregnancy stages

Known as the first, second and third trimester

Key points about pregnancy stages

  • The average length of pregnancy is 40 weeks, starting from the first day of your last menstrual period to the birth of your baby.
  • Most babies are born somewhere between 38 to 42 weeks.
  • Pregnancy is divided into 3 stages of 3 months each, known as a trimester.
  • The first trimester takes you to 12–14 weeks gestation.
  • The second trimester up to 28 weeks gestation.
  • The third trimester finishes with the birth of your baby. 
  • Being aware of the specific ways that your growing baby is affecting your body in each trimester.
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The first 3-month period begins before you are even pregnant. It starts with your last menstrual period and includes conception, which on average happens 14 days later. For the first 8 weeks, your baby is known as an embryo, after which it is known as a foetus.

During the first trimester, your baby changes from a single fertilised cell into an embryo that implants itself in your uterine wall. Over the next few weeks, the embryo beings to grow rapidly as the heart and nervous system begin to form and limb buds appear.

By the end of this trimester, your baby is moving freely (although you cannot feel this yet), the circulation and the kidneys are working and the baby is sucking and swallowing. A placenta has developed which ensures the baby receives oxygen, blood supply and nutrients to grow and survive. The baby is attached to the placenta by the umbilical cord.

What's happening to mum?

You may not look pregnant yet – but chances are you're feeling it. In the first few weeks following conception, your hormone levels change significantly as your uterus begins to support the growth of the placenta and the foetus. You may start to experience pregnancy symptoms, such as overwhelming tiredness, morning sickness, breast tenderness, a metallic taste and frequent urination.

As well as coping with the physical changes, the first trimester is a time to come to terms with the reality of being pregnant and to start to prepare mentally for the changes it will bring.

First trimester to-do's

1. Choose your lead maternity carer (LMC) ­ 

As soon as your pregnancy is confirmed you need to choose a lead maternity carer or LMC. Your LMC is the person who will help to guide you through your pregnancy, the birth of your child and the first 4–6 weeks of parenthood.

Most LMCs are registered midwives, but they can also be family doctors who provide maternity care or obstetricians (doctors who specialise in pregnancy and childbirth).

  • Mum2Be helpline. Phone 0800 MUM 2 BE (0800 686 223) to get lead maternity carers in your area.
  • Find a midwife(external link) This website lists contact details for qualified midwives who are members of the NZ College of Midwives.

2. Health tests and screening

When you first see your family doctor, midwife or specialist doctor during pregnancy, you will be offered a blood test. This blood test is free and from one blood sample the following are checked:

An optional test is antenatal screening for Down syndrome and other conditions. Read more about antenatal blood tests.

3. Be aware of red flag symptoms

Any of these symptoms could be a sign that something is wrong with your pregnancy. Don't wait for your regular prenatal visit to talk about any of these. Call your doctor or LMC right away if you experience:

  • severe abdominal pain or cramps
  • severe nausea or vomiting
  • bleeding
  • severe dizziness
  • pain or burning during urination.

4. Learn about labour, birth and looking after a baby

Many women, especially those expecting their first baby, go to classes to learn more about pregnancy, giving birth and parenting. These classes also provide an opportunity to meet other pregnant women – many groups go on to have regular catch-ups after their babies are born.

Talk to your LMC about the classes that are available in your area. Most district health boards(external link) provide a limited number of free classes. There are also privately run classes; you will have to pay for these. 

5. Find out about parental leave

You can get up to 10 days unpaid special leave while you're pregnant. This is for medical appointments, antenatal classes etc and doesn't have to be taken as a full day's leave. Find out what paid and unpaid parental leave you're entitled to and how to apply for it at types of parental leave(external link).

Staying healthy in the first trimester

The first trimester is vital for the development of your baby. Your baby will develop all of its organs by the end of the third month. To stay healthy and support this growth read about:

Video: Health Nav chat w/ Emma Parry - Pregnancy

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The second trimester (weeks 13–27) is often the most comfortable stage for pregnant women, as most of the early pregnancy symptoms gradually disappear. You’ll start to notice a baby 'bump' and at around 20 weeks you’ll also start to feel tiny flutters as baby moves.

Baby’s growth during the second trimester

At the beginning of the second trimester, your baby is about the size of half a banana, their body is covered with soft downy hair and fingerprints have formed. The next 3 months is a time of rapid growth, which will see fingernails, eyes, eyelashes and eyebrows and genitals all form. By the end of this trimester, the digestive system is working and the lungs are getting ready to breathe. Your baby can hear and respond to voices and will have a pattern of sleep-wake times. Eyes begin to open and finger and thumb sucking takes place.

What’s happening to mum?

While the discomforts of early pregnancy should ease off, there are a few new symptoms to get used to. Common complaints include leg cramps and heartburn. You might find yourself growing more of an appetite, and your weight gain will accelerate. Learn about eating, drinking and watching your weight during pregnancy.

You will be seeing your lead maternity carer (LMC) once every 2 to 4 weeks to ensure the ongoing health of you and your baby. This is also a good opportunity for you to ask questions about any pregnancy-related issues that might be concerning you.

Red flag symptoms

Any of these symptoms could be a sign that something is wrong with your pregnancy. Don't wait for your regular prenatal visit to talk about them. Call your doctor or LMC right away if you experience:

  • severe abdominal pain or cramps
  • severe nausea or vomiting
  • bleeding
  • severe dizziness
  • pain or burning during urination.

Screening tests and checks

20-week anatomy scan

An anatomy ultrasound might be performed between weeks 18 and 22. At this scan, parts of the baby’s body will be measured and assessed to make sure that they are functioning. At the anatomy scan, you may be able to find out the sex of your baby. Let your doctor know if you would like to know, or if you don't want to know.

Gestational diabetes blood test

Gestational diabetes can be detected between weeks 26 and 28 of pregnancy. To test for this, you’ll be given a high-glucose solution to drink. After drinking it, you’ll be asked to wait an hour before having your blood taken. This test will ensure that your body reacts properly to sugar during your pregnancy.

Start spreading the news!

If you haven’t done so already, now’s a good time to let family and friends know about your pregnancy. If you have kept it quiet, your expanding belly will be starting to give you away! Whether your pregnancy was planned or not, engaging the love and support of those around you will help make the coming months easier.

When you reach the third trimester of pregnancy, you're on the home stretch. You'll be looking forward to seeing your baby face to face but before you do, there's still a few more weeks of growing to get through. Here's what to expect in these final few weeks.

Baby’s growth during the third trimester

Your baby will be rapidly putting on weight in the third trimester as fat stores are developed in preparation for birth. Your baby will have established sleep-wake routines and you will be able to tell by their movements the times when they are active and awake.

The average length of pregnancy is 40 weeks, with most babies being born somewhere between 38 to 42 weeks. By the 37th week, all your baby’s systems and organs will have developed to a point that means your baby is able to survive without medical assistance if born after this time.

What's happening to mum?

In the third trimester, the extra weight you’re carrying may be making you feel cumbersome and tired, and your back may feel achy and sore. You might also feel discomfort in your pelvis and hips as your ligaments loosen to prepare for labour. Your growing baby will be putting pressure on all your internal organs, which can lead to you experiencing common pregnancy complaints such as the need to go to the toilet all the time, heartburn and breathlessness. You might start to feel mild contractions known as Braxton Hicks contractions, which are warm-ups to prepare your uterus for the real labour to come.

Despite all these discomforts, many women find the third trimester a time of great excitement as they make final plans in preparation for the imminent birth of their baby.

To ensure the ongoing health of you and your baby, visits with your lead maternity carer (LMC) become more frequent as the due date approaches. This is also a good opportunity for you to ask questions about anything that might be concerning you. 

Red flag symptoms

Any of these symptoms could be a sign that something is wrong with your pregnancy. Don't wait for your regular prenatal visit to talk about them. Call your doctor or LMC right away if you experience:

  • severe abdominal pain or cramps
  • severe nausea or vomiting
  • bleeding
  • severe dizziness
  • pain or burning during urination
  • baby not moving as normal.

Brochures

Pregnancy and parenting education for you and your whānau [PDF, 2 MB] Auckland DHB, NZ
Antenatal care during pregnancy(external link) RANZCOG, NZ, 2021
Prenatal screening for chromosomal and genetic conditions(external link) RANZCOG, Australia, 2017
Breech presentation at the end of your pregnancy(external link) RANZCOG, 2021
Assisted birth(external link) RANZCOG, 2021
Caesarean section(external link) RANZCOG, 2021
Induction of labour(external link) RANZCOG, 2021
Labour and birth(external link) RANZCOG, 2016
Pain relief in labour and childbirth(external link) RANZCOG, Australia, 2016
Whakatipu Te Kākano(external link) Te Kākano is the journey of whānau and their growing pēpi during hapūtanga. This booklet offers ideas and simple whānau tikanga relevant to pregnancy. Takai, NZ, 2023

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Credits: Healthify Editorial Team. Healthify is brought to you by Health Navigator Charitable Trust.

Reviewed by: Lee-Ora Lusis, Clinical Nurse Director, Totara Health

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