An Overview of the Pregnancy Trimesters

Being pregnant is an unforgettable experience for parents-to-be. As you make your way through each of the three pregnancy trimesters, 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 developmental highlights, symptoms, and things to consider during the weeks of your first, second, and third trimesters of pregnancy. Read on to discover what's coming up in each stage of your exciting pregnancy journey!

What are the Trimesters of Pregnancy?

Let’s start with the common question, “How many trimesters are in a pregnancy?” Pregnancies consist of 3 stages, commonly referred to as trimesters. Your healthcare provider will likely refer to your pregnancy in weeks. The weeks of pregnancy are grouped into trimesters, each of which is about 12 or 13 weeks long. Here’s how the weeks of pregnancy are split into trimesters:

• First trimester: first day of your last menstrual period to 13 weeks and 6 days

• Second trimester: 14 weeks to 27 weeks and 6 days

• Third trimester: 28 weeks to 40 weeks and 6 days.

How Long Is a Pregnancy?

So, how many weeks is a pregnancy? The average pregnancy is about 40 weeks long. The weeks of pregnancy are counted from the first day of your last menstrual period, which means an extra two weeks are counted at the beginning when you aren’t actually pregnant yet. 

Wondering how long a pregnancy is in months? 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.

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 below. Remember that though a typical pregnancy lasts about 40 weeks, most pregnant people give birth within about two weeks of their estimated due date.

First Trimester: Weeks 1 to 13

Congratulations—the first trimester is here and you’re going to have a baby! This is exciting news and we’re happy to help guide you as you begin your pregnancy journey. 

Now let’s get down to the details: How long is the first trimester and when does it end? The first trimester starts from the first day of your last menstrual period and lasts until 13 weeks and 6 days. This means your first trimester starts when you’re not technically pregnant. Don’t worry if this seems confusing, your healthcare provider will help explain it to you and give you your estimated due date.

Your Baby’s Development

What are the developmental stages of a fetus in the first trimester? In the first few weeks, 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 the 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 just yet.

And it’s still too early to find out whether you’re having a little boy or girl, but that doesn’t mean you can’t have a little fun guessing! Try our fun (and unscientific) quiz to guess your baby’s gender.

First Trimester Symptoms

Some of the early signs of pregnancy that you might be experiencing during the weeks of the first trimester include:

• Morning sickness. Morning sickness is a common symptom during the first stage of pregnancy. Contrary to what the name suggests, it doesn’t only occur in the morning. Not all pregnant people experience these queasy feelings, but for those who do, nausea and sometimes vomiting typically happen between weeks 4 and 9 of pregnancy, generally subsiding in the early part of the second trimester.  If you are experiencing morning sickness, there are several strategies you can try to feel better: 

  • Stay hydrated 

  • Eat bland foods like toast and bananas 

  • Consume small meals more frequently throughout the day  

  • Avoid smells or foods that trigger your nausea 

  • Try consuming ginger, such as ginger tea or ginger candies

  • Consult your healthcare provider for personalized recommendations that suit your situation.

• Spotting. Early in the first trimester, you might notice some spots of blood on your panties. 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. It’s normal to experience mood changes during pregnancy, ranging from joy about becoming a parent to anxiety about new responsibilities. You might also feel frustrated with physical symptoms. Mood swings are common, so consider discussing your feelings with loved ones. If the swings are severe, consult your healthcare provider.

• Weight changes. Both 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. You can read more about weight gain during pregnancy in our informative article, and try our Pregnancy Weight Gain Calculator below to help you keep track.

Things to Keep in Mind for This Trimester

• Healthcare. Look into what healthcare services are available to you during pregnancy, and select a healthcare provider if you haven't done that yet. You can read more about finding a good prenatal healthcare provider in our dedicated article.

• First prenatal visit. At your first prenatal care visit your provider 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 parents-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 may be eligible for some paid or unpaid leave during and after pregnancy. Find out what rights you have, including under your state’s laws. Some workplaces also offer additional benefits. Your partner should also look into what paternity leave options are available. You should also research when you’ll need to tell your employer about any leave you’ll be taking, and whether you need to complete any additional paperwork.

Second Trimester: Weeks 14 to 27

If you’re experiencing some uncomfortable symptoms in the early stages of pregnancy, you may be wondering “When does the second trimester start?”. The good news is that the second trimester, starting at week 14, which is month 4 of pregnancy, may be much more enjoyable than the first! This is sometimes called the “honeymoon period,” when some pregnancy symptoms subside and many pregnant individuals experience a surge in energy.

Your Baby’s Development

Your baby is busy in there! So, which fetal developments occur during the second trimester? During this trimester your little one will begin to hear sounds and will even respond to loud or familiar sounds. A waxy coating called vernix will cover the skin, protecting it from the fluids in the amniotic sac. Downy hair called lanugo will grow all over your baby’s body—in fact, some babies are even born with patches of lanugo. 

By the end of this trimester, your baby’s fingers and toes will be completely formed, and your little one will have unique fingerprints! You will likely begin to feel your baby moving around during this trimester. This sensation is known as quickening.

Towards the end of this stage, your baby will start to grow more rapidly, including putting on more fat.

Second Trimester Symptoms

Although this is a much more comfortable time for many pregnant people, there may still be some discomfort! Here are some of the potential symptoms in the second trimester of pregnancy:

• Round ligament pain. Bands of connective tissue called round ligaments pull and stretch to support your growing uterus. As this happens, you may feel a dull ache or sharp pain on one side of your abdomen. To help relieve the pain, try changing positions, or, conversely, try not moving for a little while. 

• Headaches. If you experience mild headaches in the second trimester, try lying down with a cool pack on your head. If you experience a severe headache that just doesn’t seem to go away, tell your healthcare provider, as it could be a sign of something more serious.

• Cravings. It’s quite common to crave certain foods during pregnancy. Give in to your cravings occasionally, but don't completely abandon your healthy eating habits. If you crave things like clay, starch, or chalk, definitely don’t eat them and contact your healthcare provider as it could mean you’re missing some nutrients.

Things to Keep in Mind for This Trimester

• Feeling your baby move. At some point in this trimester, you will start to feel your baby move. Each pregnancy is unique, so if you’re concerned about when you will feel a flutter for the first time, consult your healthcare provider. After you’ve felt your baby move, there is no need to constantly worry about their movements for the rest of your pregnancy. However, if you notice a significant decrease in movement compared to what’s normal for you, it’s important to inform your healthcare provider. A good way to keep track is to count 10 distinct movements in a two-hour period. For more on this, check out our Fetal Movement Tracker.

• Finding out your baby’s gender. Around week 20, your healthcare provider will likely schedule a mid-pregnancy ultrasound scan. During this scan, if you want to, you can find out the gender of your baby. Once you find out and are ready to share this news with family and friends, you might consider asking the host of your baby shower to include a special gender reveal moment.

• Planning a babymoon. If you’re feeling good and are experiencing an energy boost, this could be a good time to take a vacation. Get the all-clear from your healthcare provider, and check out our guide to travel during pregnancy for tips and guidance. You might also enjoy our fun quiz to discover your ideal babymoon destination.

• Getting your home ready. Now could be a good time to start researching and organizing the things you’ll need for your baby, like furniture for the nursery, a car seat and a high chair, newborn clothes, and baby care essentials like diapers. You could also babyproof your home now to get these kinds of bigger jobs out of the way. 

• Prenatal exercise. If you haven’t already, add some gentle exercise to your routine, after checking in with your healthcare provider. Good options could include walking, swimming, and yoga.

• Gift registry. Put together your gift registry, as the host of your baby shower may need it soon! Struggling with what to include? Take a look at our baby registry checklist.

• Find out much more about the second trimester in our dedicated article.

Third Trimester: Weeks 28 to 40

As you draw nearer to your final trimester (and meeting your baby!), you may wonder “When does the third trimester start?” 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 their eyelids and sense bright lights. Your baby’s brain, lungs, and nervous system are maturing rapidly and finishing their development by the end of this trimester. 

Your little one’s bones are hardening, though their skull remains soft. They may be gaining about half a pound per week and are putting on extra fat too, so their skin is less wrinkly by the middle of this trimester. 

As your baby grows, they won’t have as much room for somersaults, but you’ll still feel them 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 and measure 18 to 20 inches long.

Third Trimester Symptoms

As you prepare for your new arrival, you may be feeling busy yet excited, and you’ll likely be experiencing certain discomforts as your baby and uterus grow and your body prepares for labor. You’re carrying an extra load right now, so remember to get plenty of rest and take care of yourself. Here are some symptoms in the third trimester of pregnancy:

• Feeling short of breath. As your uterus grows and presses up towards your lungs, you may feel short of breath. Practicing 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 “practice” 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 labor. But, if your contractions become regular or more painful over time, or if you’re at all unsure about whether you’re feeling practice or true labor contractions, contact your healthcare provider right away.

Related Articles

Full-Term Pregnancy Explained

Things to Keep in Mind for This Trimester

• Prenatal classes. Register 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. You can also register to watch our free online birthing classes.

• 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 labor 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 favorites.

• Pampers Rewards. Download the Pampers Rewards app so that you can pick up fantastic rewards and discounts for all those diapers you’ll be buying.

• Find out much more about the third trimester in our dedicated article.

The Bottom Line

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!