First Trimester of Pregnancy: 0-13 Weeks of Pregnancy

Congratulation’s mom-to-be! Your beautiful journey of pregnancy has just begun, and you may be having lots of questions already. It's natural to be curious about what’s in store for you ahead. Read on to understand all about foetal development during the first trimester, the first weeks of pregnancy symptoms, and more.

How Long Is the First Trimester?

Did you know? Your first trimester of pregnancy begins even before you become pregnant. No, that's not written by mistake, and you read it right. Usually, your estimated due date is calculated from the first day of your last menstrual period (LMP). As a full-term pregnancy is about 40 weeks long, your doctor calculates 40 weeks from the start of your last period to estimate your baby's arrival date.

If you are yet to visit your doctor for confirmation, you can use our Due Date Calculator to get a quick estimate. You can also read about how far along you are to get a clear idea of this. Although, pregnancy goes on for about 40 weeks, not all babies are born exactly on their due date. A due date is just an estimate, which helps you prepare for your delivery date. It is normal for babies to be born either two weeks before or after the due date. Keep in mind, your pregnancy is considered full -term at the start of 39 weeks, whereas the trimesters of pregnancy are composed of 40 weeks.

As 40 weeks can’t be divided neatly into 9 months of pregnancy, there is some variance in the grouping of weeks into months. Moreover, months are typically longer than four weeks, hence the trimesters of pregnancy are also broken down into months.

Your Baby’s Development in the First Trimester

During the 1st trimester of pregnancy, what starts as a tiny bundle of cells quickly turns into an embryo and then a foetus that's about the size of a large plum.

In these first few weeks of pregnancy, your little one’s brain, spinal cord, heart, and tiny limbs — complete with fingers and toes — will form.

Meanwhile, your uterus is becoming a comfortable home for your little one, who will be nourished by the developing placenta and umbilical cord.

By the end of the third month of pregnancy, all essential organs and body parts will be in place — albeit in teeny-tiny size.

A lot is happening in the first trimester. Here are a few of the most exciting foetal development milestones:

  • 4 Weeks – implantation:

The ball of rapidly dividing cells, called a blastocyst, implants in the uterus. This is when some moms-to-be experience implantation bleeding. The inner cells will become the embryo and the outer cells will become the placenta. The placenta will provide nourishment to your baby from now until delivery.

  • 6 Weeks - taking shape:

Around six and seven weeks, the heart, lungs, and other key organs start to develop, and the head and limbs also take shape. What was a ball of cells just weeks ago is forming a more recognizable c-shape.

  • 9 Weeks - in motion:

From around nine weeks, your little one, now known as a foetus, may start moving around. However, you probably won't be able to feel any movement until the second trimester. For more on this topic, read up on quickening and foetal movement.

  • 10 Weeks - fingers and toes:

This week your baby's fingers and toes lose their webbing and continue to grow longer. It won't be long until you're able to count them!

  • 10 or 11 Weeks - the sound of your baby’s heart:

From around 10 or 11 weeks, your little one’s heart may be beating loudly enough to be heard with a Doppler ultrasound, which your healthcare provider may perform at your next appointment.

Illustration of Fetal Development Week by Week 

Take a look at the illustration below to understand how your little one may develop week to week during the first trimester: 

Pregnancy Calendar Trimesters

First Trimester Pregnancy Signs

Although every pregnancy is unique, here are some of the most common symptoms of the first trimester:

  • Emotional ups and downs:

The first stage of this journey may be a bit of a rollercoaster ride, but that’s hardly surprising as something amazing is happening in your belly and you’re at the start of a new journey. The rush of hormones in early pregnancy can also trigger more intense mood swings than you may be used to. Don’t be surprised if you feel a little differently about being pregnant than you had expected. Besides feelings of joy and excitement, you might also have worries or concerns about how pregnancy and having a baby will change your life. It’s helpful to talk about these mood swings during pregnancy & feelings, either with a professional or with your support network of friends and family.

  • Changes in breasts and skin:

Pregnancy hormones could be making your breasts heavier, and a little sore or tender. With all that extra blood to carry around your body, your veins may be more visible through your skin. Meanwhile, those hormones may also make your skin, moles, and birthmarks or your nipples a little darker. Most of these changes gradually fade away after you give birth.

  • Fatigue:

Feeling tired or exhausted is particularly common in the first trimester, as your hormones go into overdrive. The best thing you can do if you’re experiencing pregnancy fatigue is to get plenty of rest. Maintaining a healthy diet during pregnancy and doing gentle exercise might also help you feel better.

  • Nausea:

The queasiness (and sometimes vomiting) known as morning sickness may appear in the first trimester. Contrary to its name, though, it doesn’t strike only in the mornings! Try to think of morning sickness as a reassuring reminder that you are pregnant. You might be able to ease some of the symptoms with a few lifestyle changes, like avoiding food or smells that trigger your nausea, and eating smaller, more frequent meals of plain, low-fat foods. You may find cold foods easier to stomach than hot meals. Food or drink that contains ginger may also help take the edge off your queasiness.

  • Cravings:

Weird as they are, pregnancy cravings for unusual foods are usually nothing to worry about. However, talk to your ob-gyn doctor right away if you start to crave non-food items like soil or paper.

  • Frequent urination:

With rapid hormonal changes and your body’s organs working harder than usual, you may find yourself needing to pee more often than usual.

  • Acne:

An increase in oil production triggered by hormones can clog pores and lead to acne in some moms-to-be. Wash your face twice a day, go for oil-free cosmetics, and ask your doctor about any medications that can help reduce breakouts.

What’s in Store for You This Trimester?

Here are just some of the things you may be doing or that may be coming your way in the first trimester:

  • Confirming your pregnancy:

A home pregnancy test is the best way to confirm your pregnancy when not sure. However, consult your doctor in case of any doubts. If you haven't found a prenatal doctor yet, now is the right time to do so.

  • Determining your due date:

Soon after knowing you're pregnant, you’ll be excited about the date of your baby's birth. Until you meet your doctor, look at our handy Due Date Calculator. This tool will provide an estimate of your due date based on the first day of your last period or the date of conception. Your doctor will also give you an estimate of your due date at your first prenatal visit.

  • Sharing the good news:

If you haven't shared the special news with your partner yet, here are some fun ways to tell your partner you’re pregnant. Whether you go with something funny, romantic, or downright creative, your partner will love your surprise!

  • Announcing your pregnancy:

When to share the news of your pregnancy with loved ones is a personal choice. However, some expecting moms choose to wait until the beginning of the second trimester to share the news.

  • Experiencing shifting emotions:

Pregnancy hormones can cause more intense mood swings than you may be used to. It is completely natural to feel different about your pregnancy than what you had expected.

  • Working through pregnancy symptoms:

Although the first trimester symptoms may seem annoying, the good news is each symptom reminds you of how you will be bringing a new life into this world. With each week of pregnancy, you will experience something new and interesting, reminding you that these symptoms won't last forever. Usually, the early pregnancy symptoms subside around the second trimester.

  • Going to your first prenatal care check-up:

It is time for you to schedule your first prenatal check-up if you haven't already. Your doctor will set up many check-ups to monitor your and your baby’s health. During the first visit, your doctor will ask you about your medical history, run tests and do a physical exam, and give you an estimate of your due date. Make a list of questions that you can take to your first check-up to get all your queries answered.

  • Having tests and ultrasounds:

You may have at least one ultrasound scan scheduled in the first trimester. During the ultrasound, your doctor will be able to provide you with a more accurate estimate of your due date and will also tell you how many weeks pregnant you are. Your doctor may also suggest some screening tests that typically include a blood test and an ultrasound scan for genetic conditions. Keep in mind that these tests are optional and used to evaluate the possible risk of various conditions. Once you get the results, you can choose to have more thorough diagnostic tests done. Your doctor will explain your options to you, including any risks and benefits, so you can make an informed choice.

  • Learning you’re having twins:

There’s a slight chance that your ultrasound can show if you’re pregnant with twins, triplets, or more by the time you’re 12 weeks pregnant. If you do happen to be pregnant with more than one, read our FAQ on twin pregnancy for the lowdown on twin pregnancy.

  • Becoming informed:

Read up on pregnancy, childbirth, and child development, especially if this is your first pregnancy. It might help you feel calmer and in control of what’s to come. Also, try talking to other moms in your area, who will have lots of personal insights and valuable experiences to share. Take a look at what's in store for you with our week-by-week pregnancy guide.

  • Making some healthy lifestyle changes:

Following a healthy routine is important not only for you but for your baby as well. Eat a healthy, balanced diet to help with morning sickness and cravings. Speak to your doctor about your calorie and nutritional needs during pregnancy and ask whether you need to take prenatal vitamins. Alcohol, smoking, and drugs can be harmful, so it’s best to steer clear of these. Start exercising or keep up with your exercise routine after checking with your doctor to learn what exercise is safe for you to do during pregnancy.

  • Practising prenatal yoga:

Prenatal yoga encourages stretching, focused breathing, and mental centring. It will also help you to calm down and reduce stress, while promoting sleep, strength, flexibility.

  • Resting and relaxing:

Building a new life takes a lot of energy. So, conserve your energy, rest enough and stay hydrated.

What Weeks and Months Are in the First Trimester? 

You may be wondering which weeks and months make up the first trimester. When the weeks of pregnancy are grouped into months, there’s some variance in how this is done. This is because 40 weeks can't be divided neatly into nine months and because months typically are a little longer than four weeks. But if you’re wondering how many months is the first trimester, it’s generally considered to be about three months long, or 13 weeks, as we mentioned above. 

Precautions to Take During the First Trimester of Pregnancy 

During your 1st trimester of pregnancy, it’s important to take precautions and prioritize your health and that of your developing baby. Here are some considerations to keep in mind now and throughout your pregnancy journey: 

  • Steer clear of alcohol, tobacco, secondhand smoke, and illicit substances, as they can pose serious risks to your baby's health and lead to complications. 

  • Be mindful of your caffeine intake and limit it to less than 200 mg a day. Caffeine can be found in chocolate, some teas, colas, and, of course, coffee. 

  • Avoid foods such as raw or undercooked seafood, raw eggs, unpasteurized milk, and soft cheeses. 

  • Check in with your healthcare provider before taking any prescription and over-the-counter medications. 

  • Be cautious of hazards that you may be exposed to in your environment, such as harmful ingredients in pesticides, cleaning products, and materials in your workplace. 

  • Minimize exposure to radiation, including X-rays and other medical imaging techniques, unless it is absolutely necessary. 

  • Engage in gentle exercise during pregnancy, checking with your healthcare provider to ensure that what you're doing is safe for you and your baby. 

  • Avoid saunas and hot tubs, as high temperatures may be harmful to your baby. 

Remember, your healthcare provider is there to support you during this important time. Don't hesitate to reach out if you have any concerns or questions. 

When to Contact Your Healthcare Provider 

It’s essential to stay in touch with your healthcare provider throughout your pregnancy, particularly during the critical first trimester, and to go to all of your prenatal checkups. While some discomforts, like morning sickness or fatigue, are considered normal during the first trimester of pregnancy, certain symptoms may warrant immediate contact with your healthcare provider. These include the following: 

  • Persistent severe abdominal pain 

  • Heavy bleeding or spotting 

  • Severe dizziness or fainting 

  • Sudden severe swelling in your hands, feet, or face 

  • Consistent severe headaches 

  • High fever or chills 

  • Difficulty breathing 

  • Persistent vomiting or inability to keep down fluids 

  • Signs of dehydration (dry mouth, not urinating regularly, feeling dizzy when standing up) 

  • Blurred vision or spots before your eyes 

  • Any other symptom that feels unusual or concerns you. 

Remember, your healthcare provider is your best resource for any questions or concerns you may have during your first trimester of pregnancy. It's better to be safe and reach out, even if you're unsure whether your symptoms are cause for concern. 

Checklist for the First Trimester

Now that you have stepped into the first phase of this wonderful journey, here is a small checklist to help you stay on track:

  • Find baby names:

Deciding on a baby name can be a long-term task with different opinions of the family members. So, it's better to start looking for baby names right from the beginning. You can explore options from mythological names, regional names, or names starting with specific alphabets. Try out our fun tool called Baby Name Generator to find some cool names.

  • Practise Garbh Sankar:

Garbh Sanskar helps you educate your baby right within the womb. Read up on what is Garbh Sanskar and how it is done here. Download our Pampers app to check our Garbh Sanskar tool.

  • Look forward to the Godh Bharai ceremony:

The Indian baby shower is a 'women-only' ritual full of enthusiasm, sweets, guests, gifts, dance, and fun. It is a celebration organised by close family members to welcome the baby and is hosted around the seventh or eighth month of pregnancy. To know more, read here.

  • Look up for childbirth classes:

Childbirth classes teach you breathing techniques and exercises that will help you during labour and delivery. So, you can start researching a bit about these and start searching for the best ones near you.

  • Join forums or communities:

Nobody can understand your emotion like another mom-to-be or experienced moms. Sign up on forums or join a network of moms to share your thoughts, get answers to your queries, and more.


Some good foods to eat in your first trimester of pregnancy if you’re suffering from morning sickness include easy-to-digest foods like bananas, rice, applesauce, and toast. Taking a daily prenatal vitamin may also help reduce the risk of severe pregnancy-induced nausea. You can also try ginger in the form of ginger ale, tea, or candies to help settle your stomach during periods of nausea. 

How we wrote this article The information in this article is based on the expert advice found in trusted medical and government sources. You can find a full list of sources used for this article below. The content on this page should not replace professional medical advice. Always consult medical professionals for full diagnosis and treatment.