Pregnancy trimesters & weeks

An Overview of the Pregnancy Trimesters

1
September 20, 2019
5 min read

Being pregnant is an unforgettable experience for every mom-to-be. As you make your way through each of the three trimesters of pregnancy, we'll introduce you to the changes and symptoms you're likely to encounter, as well as the many ways your baby will grow and develop. Read on for a breakdown of some of the highlights in your exciting journey — we can't wait to share what's coming up in each stage of pregnancy!

What's in this article:

The Stages of Pregnancy: The First, Second, and Third Trimester A Closer Look at the First Trimester A Closer Look at the Third Trimester

The Stages of Pregnancy: The First, Second, and Third Trimester

A normal pregnancy is about 40 weeks long. The weeks are counted from the first day of your last menstrual period, which means an extra two weeks are counted at the beginning when you weren’t actually pregnant yet. A typical pregnancy is also actually about 10 months long, not the 9 months that most people think of. Your healthcare provider is more likely to refer to the weeks instead of the months. The weeks of pregnancy are also grouped into trimesters, each of which is about 12 or 13 weeks long. So, how many trimesters are in a pregnancy? Three. And here’s how the weeks of pregnancy break down:

  • First trimester: weeks 1-13
  • Second trimester: weeks 14-27
  • Third trimester: weeks 28-42

Determining how far along you are in your pregnancy helps your healthcare provider check the progress of your baby’s growth, guides the timing of certain prenatal tests, and allows your provider to more accurately assess your pregnancy symptoms.

Your healthcare provider will assess when your baby is due, but you can get an approximate date using our Due Date Calculator tool. Keep in mind that though a typical pregnancy lasts about 40 weeks, most moms-to-be give birth in within about two weeks of their estimated due date. It also helps to estimate approximate pregnancy trimester dates.

A Closer Look at the First Trimester

Congratulations — you’re going to have a baby! This is exciting news, and we’re happy for you. Although it’s still too early to find out whether you’re having a little boy or girl, that doesn’t mean you can’t have a little fun guessing! What does our quiz tell you? Are you having a boy or girl?

Your Baby’s Development

In the first few weeks of the first trimester, all the things your baby needs to grow in the uterus will form, including the placenta, the umbilical cord, and the amniotic sac that will fill with amniotic fluid. Starting off as a bundle of cells, your little one will soon begin to develop a spine; the major organs such as brain, heart, and lungs; basic facial features like the nose, eyes, and mouth; and buds that will grow into arms and legs. Your baby's skin will still be thin and transparent at the end of the trimester, but will soon thicken, and soft nails will also begin to grow.

Although your baby’s muscles will begin to develop and your little one will be able to move, it’s still too early for you to feel these flutters yet.

First Trimester Symptoms

Some of the early signs of pregnancy include:

  • Morning sickness. This is a well-known symptom during the first stage of pregnancy. However, contrary to its name, morning sickness doesn’t necessarily strike only in the morning. Not all women experience these queasy feelings; for those moms-to-be who do, the nausea and sometimes vomiting often crop up between week 4 and week 9 of pregnancy and go away early in the second trimester. If you do have morning sickness, there are some things you can try that might help you feel better. For example, keep hydrated, try eating bland foods like toast and bananas, eat small meals more frequently throughout the day, and avoid smells or foods that make you want to vomit. You could also ask your healthcare provider for recommendations on what’s right for you.
  • Spotting. Early in the first trimester you might notice some spots of blood on your underwear. This spotting could be implantation bleeding, which happens when the fertilized egg attaches to the lining of the uterus. If you notice heavier bleeding in the first trimester, or at any time during pregnancy, contact your healthcare provider.
  • Mood swings. You may find your mood changes from one moment to the next, and you might have different feelings than you had expected. It’s natural to go through a range of emotions, from the joy of knowing that you’ll soon become a parent to anxiety about the responsibilities and lifestyle changes parenthood demands. You might even feel frustrated with the physical symptoms you’re experiencing. Mood swings can be totally normal, and it might help to speak to your loved ones about how you’re feeling. If your mood swings seem severe, ask your healthcare provider for advice.
  • Weight changes. Gaining weight and losing weight can be normal in the first trimester. If you have severe morning sickness, you may find it hard to keep food down, resulting in a little weight loss. Although experts typically recommend gaining weight steadily, you may find that you put on most of the pounds in the second and third trimesters and only gain a little in the first trimester. Ask your healthcare provider about what’s right for your situation.

Things to Keep in Mind for This Trimester

  • Healthcare. Look into what healthcare services are available to you during pregnancy (this may depend on where you live), and select a healthcare provider if you haven't done that yet. You can read more about finding a good prenatal healthcare provider here.
  • First prenatal visit. At your first prenatal care visit, your doctor may schedule any first trimester screening tests or scans. This appointment is a good opportunity for you to ask any questions or raise any concerns you have. Your provider may also make some recommendations, including taking supplements such as folic acid, adjusting the medications you take, or giving advice on healthy lifestyle changes.
  • Announcing your pregnancy. When to tell people you are pregnant is a personal choice. Many moms-to-be wait until the second trimester, when the risk of miscarriage is lower, but the choice is yours.
  • Maternity leave. If you work, you are eligible to receive employment insurance maternity and parental benefits. You can learn more about applying for EI maternity benefits from the government of Canada here.
  • Find out much more about the first trimester here.

A Closer Look at the Third Trimester

The third trimester starts at week 28 and ends when your baby is born! Your baby is considered full term at week 39. Once you’re in this stage of pregnancy, you’re in the final stretch, both literally and figuratively! Enjoy the last few months of pregnancy and use this time to rest and get ready.

Your Baby’s Development

During the past few months your baby’s eyes have been fused shut, but early in this trimester your baby will be able to open and close his eyelids and sense bright lights. Your baby’s brain is maturing rapidly and your little one is now better able to regulate his own body temperature, so he’s no longer relying on the amniotic fluid for this. Your baby’s bones are hardening, though his skull remains soft. Your baby may be gaining about half a pound per week and is putting on extra fat too, so his skin is less wrinkly by the middle of this trimester. As your baby grows, he won’t have as much room for somersaults, but you’ll still feel your baby kicking and maybe even hiccupping. Toward the end of this trimester, your baby will have dropped lower into your pelvis in preparation for birth. By week 40, many babies weigh between 6 to 9 pounds (2.7 to 4 kilograms) and measure 18 to 20 inches (45 to 50 centimetres) long.

Third Trimester Symptoms

  • Feeling short of breath. As your uterus grows and presses up towards your lungs, you may feel short of breath. Practising good posture may help you fill your lungs more easily, but you could also try to rest more often to catch your breath.
  • Itchy skin. As your skin stretches over your growing belly and breasts, you may find it becomes very itchy. Try staying hydrated and using a moisturizer morning and night.
  • Braxton Hicks contractions. It’s normal to have false labour contractions, known as Braxton Hicks contractions, that come at random intervals, or when you move suddenly. These contractions don’t actually mean you are going into labour. But, if your contractions become regular or more painful over time, or if you’re at all unsure about whether you’re feeling the real thing, contact your healthcare provider right away.

Things to Keep in Mind for This Trimester

  • Prenatal classes. Register for and attend a course to help you feel more prepared for what's ahead. Ideas include classes on childbirth, infant CPR, breastfeeding, or baby care. Read more about how to choose a childbirth class here.
  • Birth plan. If you’re thinking of having a birth plan, consider what you’d like to include and discuss it with your healthcare provider.
  • Hospital tour. If you plan to give birth in a hospital, ask if you can take a tour. This will give you a chance to familiarize yourself with the best place to park the car and the quickest route to the labour ward. This could also be a chance to ask any questions you have about hospital policies and paperwork, what you need to take with you, and what the hospital provides.
  • Hospital bag. Pack your hospital bag nice and early and have it ready to go. We’ve got you covered with our hospital bag checklist.
  • Baby names. Settled on a name yet? If not, don’t worry! There’s still time, and with our Baby Name Generator you’ll be able to create a shortlist of favourites.
  • Pampers Rewards. Download the Pampers Rewards app so that you can pick up fantastic coupons and gifts for all those diapers you’ll be buying.
  • Find out much more about the third trimester here.

FAQs at a Glance

  • Q: What are the weeks in the trimesters of pregnancy?
  • Q: How long is each trimester?
  • Q: When is my baby full term?
  • Q: How accurate is my due date?

Now that you have an overview of the trimesters, for more detail on the stages of pregnancy take a look at our Pregnancy Calendar, where you can choose whether to get more info on a week by week, month by month, or trimester by trimester basis. There are so many exciting and interesting things happening during pregnancy and we’ve got you covered! Sign up to receive our regular emails so that you get relevant information direct to your inbox:

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ACOG: How Your Fetus Grows During Pregnancy

Book: Your Pregnancy and Childbirth: Month to Month, Sixth Edition Paperback – January 1, 2016
by American College of Obstetricians and Gynecologists (Author)

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