First trimester over

First Trimester Of Pregnancy: What To Expect

What is the first trimester of pregnancy?

Pregnancy has three trimesters or stages. Each trimester is about 13 weeks or three months long. A full-term pregnancy lasts 40 weeks or between nine and 10 months. Your healthcare provider will talk to you about fetal development in terms of weeks. Your first trimester of pregnancy lasts until the 13th week of pregnancy.

It may seem strange, but your pregnancy actually begins on the first day of your last menstrual period. This is called the gestational age of the pregnancy. A pregnancy care provider calculates your due date by adding 40 weeks to the first day of your last menstrual period. So this means, by the time you know you’re pregnant, you’re already about four weeks along. This can be very confusing!

Understanding weeks of pregnancy

The first two weeks of pregnancy are part of your normal menstrual cycle — the first week is your period and the second week is ovulation. Once you ovulate, your egg travels through your fallopian tube to your uterus. If it meets up with sperm, they combine and conception occurs (fertilization).

During the third week of pregnancy, the fertilized egg travels to your uterus. On its way down to your uterus, it divides into more cells. Once it reaches your uterus, it implants into your uterine lining. This triggers your body to recognize that you’re pregnant and a series of changes begin to happen. Most people miss their period and then get a positive pregnancy test.

How long is the first trimester?

The first trimester begins before you’re pregnant. It starts on the first day of your last menstrual period and goes until the 13th week of pregnancy.

What can I expect in my first trimester?

Your first trimester of pregnancy is full of many physical and emotional changes. It can be a very overwhelming time, and your mind may be racing with questions. Plus, your hormones are in overdrive. In fact, your body produces more estrogen during one pregnancy than it does during your entire life when you’re not pregnant. This surge in hormones can cause some unpleasant pregnancy symptoms. You may find yourself feeling moody, bloated and tired. While you may not see a prominent baby bump yet, your uterus is expanding and your blood volume is increasing.

It’s OK to feel both excited and nervous. Talking to your friends, partner or a healthcare provider may help you feel better as you navigate your pregnancy journey.

What should I do in my first trimester?

Your first trimester is very important. You might not look or feel pregnant, but lots of changes are happening.

If you don’t have a healthcare provider or a pregnancy care provider, you should find one as soon as possible. Getting early pregnancy care can help you avoid any potential complications. Make a list of questions or concerns you have so you’re ready for your first appointment. Check with your health insurance about pregnancy coverage so you know what to expect and where you can get care. If you don’t have health insurance, there are programs and agencies to help you get prenatal care.

There are different types of pregnancy care providers that take care of you during pregnancy, labor, delivery and postpartum. These include obstetricians, midwives, and sometimes, primary care physicians. In addition to selecting a pregnancy care provider, you may also consider places to deliver your baby. While most people choose to give birth in a hospital, some people prefer birthing centers or home births.

Now is a great time to think about your overall health and what lifestyle changes you may need to make now that you’re pregnant. For example, think about how pregnancy affects your work, finances, habits and daily activities.

How does the fetus develop in the first trimester of pregnancy?

Several developments occur in the first trimester. Although you can’t see it happening, there’s a lot going on inside your body after sperm fertilizes an egg.

Weeks one to four of pregnancy

During the first month of pregnancy, several important structures form. These structures are a tiny clump of cells, but will grow to become the amniotic sac, placenta and umbilical cord. A tube that becomes the fetus’s brain and spinal cord forms, as well as its circulatory system. A face, circles for eyes and the beginning of a mouth take shape.

The embryo is about a quarter-inch inch long — smaller than a grain of rice.

Weeks five to eight of pregnancy

Several major organs begin to develop during the sixth week of pregnancy including the fetal lungs, heart, ears, arms and legs. Bones begin to replace tissue. Its head is large in proportion to the rest of its body, but it look more human now. The fetus has a distinct mouth, nose and face. Some providers do an early ultrasound to confirm a heartbeat during this time.

By the end of the eighth week of pregnancy, the embryo becomes a fetus. It’s about 1 inch long or the size of a raspberry.

Weeks nine to 12 of pregnancy

Towards the end of your first trimester, the fetus will have toes, fingers and nails. It will start to move by opening and closings its hands and mouth. The fetus’s urinary and digestive systems are also fully functioning. At around 12 weeks of pregnancy, your provider can listen to the fetal heart using a Doppler ultrasound. It also has either a vagina or a penis at this point (though your provider can’t see it on an ultrasound).

By the end of the 12th week of pregnancy, the fetus is between 3 and 4 inches long — about the size of a plum. It weighs about 1 ounce.

Why is the first trimester of pregnancy so critical?

The first trimester is so important because most of the fetus’s major organs and body systems are developing. Toxins, harmful substances and infection can severely damage a fetus’s growth and development during this time. It could increase your baby’s risk of being born with a congenital disorder.

What are the most common symptoms during the first trimester?

Every person and every pregnancy is unique. An increase in hormones cause most pregnancy symptoms. Some of the most common are:

Sore breasts: Hormones may make your breasts feel tender and large. It’s common to need bigger bras before the end of your first trimester. The veins in your breasts may become noticeable because they’re carrying more blood. Other changes to your breasts may include darkened areolas or changes to your nipples.
Nausea: Morning sickness is one of the telltale signs of early pregnancy. Despite its name, it can last all day and all night. Try eating smaller meals or bland, low-fat foods. Some people find relief by eating foods containing ginger.
Mood swings: The sudden rush of hormones may put you on a rollercoaster of emotions. You may alternate between feeling anxious or scared to excited or weepy within a span of 30 minutes. It may be helpful to talk through your feelings with a friend or your partner.
Feeling tired: Your body is hard at work during the first trimester of pregnancy. This may leave you feeling exceptionally tired. Be sure to get plenty of rest. Most people get some energy back in the second trimester.
Needing to pee: Your uterus begins to grow to support the pregnancy. It may begin pressing on your bladder, causing you to need to pee more often.
Acne or other skin changes: Hormones cause your skin to create more oil during pregnancy. This can lead to clogged pores and acne in some people. There are other skin conditions that appear during pregnancy, but most appear in the second or third trimesters.
Mild shortness of breath: You may feel short of breath with light physical activity.

Your heart is pumping more blood during pregnancy. This means your pulse may be quicker and you may find yourself losing energy more easily. Be mindful of how much demand pregnancy puts on your body and take rests when you feel tired or out of breath.

What tests will I have in the first trimester of pregnancy?

Checkups, screenings and other tests during pregnancy help keep you and the fetus healthy. Care during pregnancy is commonly referred to as prenatal care. Prenatal care appointments are important because your pregnancy care provider discusses what you can expect during pregnancy and delivery, performs checkups and screenings and answers any questions you have.

Your first prenatal visit

You’ll have between two and three prenatal visits during your first trimester. This can vary depending on your provider or if you’re a high-risk pregnancy. You can expect to discuss your personal medical history, gynecological and obstetrical history (prior pregnancies and births), as well any family medical history that may affect your pregnancy. This visit is very thorough to make sure you and the growing fetus are healthy.

At your first prenatal visit your provider will calculate your due date. You can also expect them to perform the following:

A physical exam, including checking your weight and blood pressure.
A pelvic exam.
A Pap test (if you’re due for one).
Tests to check for certain sexually transmitted infections (STIs).
Check your pee for bacteria, protein and glucose (sugar).
Order blood tests to check hormone levels, Rh factor, iron levels and certain diseases.
Check the fetal heart rate.

Some providers use transvaginal ultrasound at your first appointment to confirm pregnancy and measure the fetal heart rate and size. This ultrasound also shows if you’re expecting multiples. A transvaginal ultrasound involves your provider placing a wand inside your vagina. Most pregnant people are offered at least one ultrasound in their first trimester, but the exact timing varies depending on your provider. If you’re expecting multiples, you may be offered additional ultrasounds in your first trimester.

Your provider may suggest other screening tests during pregnancy. Screening tests identify if you or the fetus are at risk for certain health conditions. Based on the results of your screening, you may need diagnostic tests. Diagnostic tests confirm or rule out health problems. In the first trimester, your provider may suggest a screening to detect a higher risk of chromosomal disorders like Down syndrome. Talk to your provider about the screenings they recommend.

What should I not do in the first trimester of pregnancy?

Once you find out you’re pregnant, it’s normal to have to make some lifestyle changes. These changes help ensure that everyone is healthy. You should avoid the following things during your first trimester of pregnancy:

Alcohol.
Cigarettes and tobacco.
Recreational drugs like opioids.
Contact sports like football or activities that put pressure on your abdomen.
Foods like raw fish (sushi), fish high in mercury, uncooked or undercooked meats, lunchmeat and unpasteurized milk, cheese or juice.
Hot tubs and saunas.

How do I take care of myself in the first trimester of pregnancy?

Staying healthy is important throughout all three trimesters of pregnancy. Here are some helpful tips on staying healthy during the first 13 weeks of pregnancy:

Stay active as much as you can. Listen to your body and stop for rest if you feel any discomfort while exercising. You may need to modify your exercise routine during pregnancy.
Take a prenatal vitamin containing folic acid.
Eat a variety of healthy foods including fruits, vegetables, meat, eggs and whole grains.
Get plenty of rest.
Drink plenty of water.
Attend all of your prenatal appointments.

Is it normal to bleed during the first trimester of pregnancy?

Light bleeding or spotting during pregnancy is usually OK in the first few weeks of pregnancy. Some people experience implantation bleeding (when a fertilized egg burrows unto your uterine lining). Call your pregnancy care provider if you’re bleeding heavily or the bleeding lasts more than one day.

What prenatal vitamin should I take?

The vitamins and minerals in your food (or in prenatal vitamins) help support the fetus as it grows and develops. Most providers recommend taking a prenatal vitamin as soon as you begin trying to get pregnant. Vitamins containing folic acid, iron and calcium help support a healthy pregnancy. Talk to your provider if you’re unsure about which prenatal vitamin to take.

Can I drink caffeine during pregnancy?

Most healthcare providers recommend limiting caffeine consumption to under 200 milligrams per day during pregnancy. That’s about 12 ounces of coffee or three cans of Mtn Dew®. This is because a fetus can’t metabolize caffeine so it can build up in their body and cause complications.

When should I call my pregnancy care provider during the first trimester?

Call your provider right away if you have:

A fever higher than 100.4 degrees Fahrenheit.
Heavy bleeding or unusual vaginal discharge.
Severe cramping in your belly, arms or legs or abdominal pain.
Persistent vomiting and/or diarrhea.
Fainting spells or dizziness.
Swelling in your hands, fingers or face.
Blurred vision or spots before your eyes.

A note from Cleveland Clinic

Pregnancy is an exciting, and sometimes scary, time in your life. You may feel overwhelmed with information and have lots of questions. During the first trimester of pregnancy, your body is growing and changing rapidly. The fetus is growing and developing, too. In fact, by the end of the first trimester, the fetus is the size of a lemon. You may begin having symptoms of pregnancy like nausea, sore breasts or needing to pee more often. Schedule an appointment with a pregnancy care provider as soon as you know you’re pregnant. Regular prenatal care is important so you and the fetus stay healthy and strong during pregnancy.

Everything you need to know about the first trimester (weeks 1 to 12)

Tommy's PregnancyHub

You’re pregnant: congratulations! The first weeks of your pregnancy are a vital time as your body gets busy building a baby. How exciting!

First trimester: key stages

The first trimester begins on the first day of your last period and lasts until the end of week 12. This means that by the time you know for sure you're pregnant, you might already be five or six weeks pregnant!

A lot happens during these first three months. The fertilised egg rapidly divides into layers of cells and implants in the wall of your womb where it carries on growing. These layers of cells become an embryo, which is what the baby is called at this stage.

During this trimester, your baby grows faster than at any other time. By six weeks, a heartbeat can usually be heard and by the end of week 12, your baby's bones, muscles and all the organs of the body have formed. At this point, your baby looks like a tiny human being and is now called a fetus. He or she will even be practising swallowing!

Try our Healthy Pregnancy Tool to find out everything you need to know about your pregnancy

When am I due?

Find out your due date using our due date calculator!

When will I see a midwife?

Your first midwife appointment (also known as antenatal appointment) is the 'booking' appointment. This usually happens between week 8 and 10 of your pregnancy. Find out how to register with a midwife and when your appointments will be here.

Keeping your baby safe

There are some things that you can do during pregnancy that have an effect on your baby. Find out about them by clicking the link below.

Find the complete list of pregnancy dos and don'ts (and reasons why) here

Not sure whether you are pregnant?

Find out about the symptoms that mean you may be pregnant here.

Your physical and mental health in pregnancy

We also have lots of useful tips for coping with everyday pregnancy niggles. It’s common for women to experience symptoms such as morning sickness, cramp and indigestion during the first trimester.

Don't forget that your mental health is just as important as your physical health. It's normal to feel some anxiety and stress but it shouldn't be ongoing. If what you’re feeling isn’t normal for you, talk to your GP or midwife about it. They are there to help.

Exercise, such as yoga, has been shown to reduce anxiety and is a great way to stay active during your pregnancy, too.

Read more about mental wellbeing in pregnancy

Track your baby's development

Sign up to a free pregnancy email from our midwives to track your baby's development and give you reminders of all you need to know through the 9 months of pregnancy. Click here to sign up.

Review dates

Reviewed: 28 June 2018 | Next review: 28 June 2021

This content is currently being reviewed by our team. Updated information will be coming soon.

9-12 weeks of pregnancy

Ninth week for the baby

During the ninth week, the weight of the fetus changes from 1 gram to 10 grams, the length is 30-45 mm. The back of the fetus straightens and the embryonic tail disappears. The future child becomes completely similar to a small person. The head at this stage is pressed to the chest, the neck is bent, the arms are also brought to the chest.

The development of the brain, which is quite intensive, is one of the main processes of this period. The cerebellum begins to function, the hemispheres acquire a clear outline. Since the cerebellum is responsible for the coordination of movements, in the fetus they cease to be spontaneous and become clear and active, the fetus begins to feel the movement of its own body. nine0005

The heart rate at this stage is 120-150 beats per minute, the heart has two ventricles and two atria. There is a circulatory system of vessels, blood begins to flow through them. While blood circulation in the upper part of the fetus is characterized by greater intensity than in the lower. Therefore, the arms are more developed in comparison with the legs. There is an elongation of the fingers, and the membranes between them slowly disappear. By the end of the ninth week, the formation of the eye ends, they are tightly covered with eyelids. There is a closing of the facial bones, on the head it is already possible to distinguish the nose and nostrils, auricles and lobes, and the upper lip. At this stage, the fetus becomes more and more like a human face. nine0005

Intensive development of internal organs leads to rounding of the tummy of the fetus. The digestive organs and the liver develop, which is important because it is responsible for hematopoiesis (the formation of new blood cells). Thus, "fetal" blood appears.

At this stage in the life of the fetus, such an important event occurs as the beginning of the synthesis of hormones, which include adrenaline. Intensive growth of the adrenal glands provides this process. Also, the beginning of the synthesis of hormones is associated with the complication of the structure of the adrenal glands. All this helps the fetus to comfortably adapt to a variety of changes and extreme conditions. It is the presence of adrenaline in the body that allows it to withstand various stresses. The fetus acquires the ability to endure stress, since adrenaline provides the regulation of a special mode of "survival". nine0005

Ninth week for the expectant mother

At this stage, the woman may still have drowsiness, fatigue, frequent mood changes and dizziness. Manifestations of toxicosis can reach their maximum. It is this period that is optimal in order to visit a gynecologist and register.

The tenth week for the baby

This week is important and significant, it is from it that the fetal stage of development begins, and the unborn child is now officially called a fetus, not an embryo. All the internal organs have already been laid, which in the future will only have to grow and develop. Experts rightly consider the tenth week to be the final one in the first critical period: from that time on, the likelihood of developing defects that may arise due to chemical factors of various nature is no longer so high. nine0005

The fetus at this time is freely located in the uterine cavity, practically not touching its walls. The future baby has an intensive formation of the nervous system, the transmission of impulses by neuromuscular pathways is being established. This process leads to the emergence of intense movements. Such movements are reflex, they are active and are caused by contact with the walls of the uterus. The fetus already makes fairly clear movements with its legs, head and handles. The woman is not yet able to feel the movements of the fetus, but they are clearly visible during an ultrasound examination. nine0005

At this time, the diaphragm is finally formed - a flat muscle designed to separate the abdominal and chest cavities. There is a further development of internal organs.

The tenth week for the expectant mother

The woman feels increased anxiety, she retains emotional lability. All this is a consequence of ongoing hormonal changes. The only thing to be understood is that the balance will soon be restored, which means the return of a stable good mood. nine0005

The situation changes with the manifestations of toxicosis. Nausea begins to disturb less and less, and vomiting, as a rule, stops altogether. Nausea mostly in the morning. If toxicosis completely disappears, increased appetite may occur. At this time, it is important to monitor the diet and prevent a sharp increase in weight. It is necessary to exclude overeating and the use of high-calorie foods. For a woman in position, this is harmful and can cause shortness of breath, swelling, deterioration of well-being. Excess weight is the reason for increasing the load on all body systems, which already spends a lot of energy on the development of the fetus. nine0005

Women in the tenth week may notice a change in the abdomen. The reason may be overeating, as well as the redistribution of subcutaneous fat and muscle relaxation due to the influence of the pregnancy hormone - progesterone.

The uterus enlarges during this period, but not so much as to influence the shape of the abdomen, it reaches the size of a large apple or grapefruit. Accordingly, for others, pregnancy is still completely invisible.

Eleventh week for baby

The fetus in the eleventh week continues to grow rapidly. Outwardly, it looks like this: a fairly large head, small legs pressed to the tummy, a small torso and well-developed long arms. Such an uneven development is due to the fact that it was the upper part of the body that received the bulk of the nutrients and the proportion of oxygen throughout the entire previous period, in which such vital organs as the heart and brain are located.

The fetus continues to form joints and bones, muscle growth. Not only large joints develop, but also small ones. In the jaws, the rudiments of teeth are formed, on the fingers - nails. nine0005

The movements of the unborn child become more and more purposeful. Loud noises and sudden movements begin to cause a response in him. Grasping and sucking reflexes develop - this can be seen in the movement of the fingers and lips. The formation of olfactory and taste buds begins. If amniotic fluid enters the nose or mouth, the fetus is able to taste it.

At this stage, the formation of the iris of the eyes also takes place, which after birth will determine their color. In newborns, in most cases, the eyes are blue or blue, brown are quite rare. The final color of the iris is formed by five months. It depends on the accumulated melanin pigment located in the iris. Genetic inheritance determines the amount of this pigment. nine0005

Eleventh week for the expectant mother

At this time, in most cases, vomiting and nausea, as well as intolerance to certain odors, disappear. Thus, a woman gets the opportunity to form a complete diet and start eating varied, giving preference to various healthy foods. It is advisable to eat freshly prepared food. If you follow a certain diet, you can avoid any problems at this time, the main of which is a problem with digestion. The relaxing hormone progesterone causes the bowel muscles to become lazy, leading to bloating and constipation. If even strict adherence to the diet does not help to cope with problems, you need to contact a specialist who can prescribe safe medications. nine0005

As the fetus grows, blood volume also increases. As a result of such changes, a woman may experience increased sweating. Increased kidney function leads to more frequent urination. If there is no discomfort and pain with frequent urination, there is no reason to worry. Otherwise, you will also need to pay a visit to a specialist. Discomfort and pain can be symptoms of inflammation of the bladder, i.e. cystitis syndromes.

At eleven weeks, the first prenatal screening is performed, which is aimed at identifying malformations. An ultrasound and biochemical study is performed. The first screening is not only aimed at identifying malformations. This examination allows you to find out the state of the chorion, the growth and degree of development of the fetus, the exact gestational age and other details. nine0005

Twelfth week for the baby

Twelfth week ends the first trimester of pregnancy. By the end of this period, the length of the fetus is 90 mm, and its weight is approximately 20 g. At this time, many significant events take place in the life of the fetus.

He has an intensive development of the brain, the formation of connections between the spinal cord and the cerebral hemispheres. If we consider the structure of the brain, it resembles a smaller version of the brain of an adult. During all the first months, only erythrocytes were in the blood of the fetus, but at the twelfth week, leukocytes, which are the body's defenders and belong to the immune system, are added to them. nine0005

The digestive tract also develops. The liver, which at this stage is the most developed organ and occupies most of the abdominal cavity, begins to produce bile, and not only provide hematopoiesis, as it was before. It is from the twelfth week that the intestine actively grows and begins to fit into loops, which can later be seen in an adult. The first peristaltic movements occur, i. e., the contraction of the muscles of the intestine, which should in the future ensure the movement of food through it. The fetus, starting from this week, swallows amniotic fluid, and they pass through the intestines. This happens before birth. Peristaltic waves are a training of the intestinal muscles. nine0005

In addition, rhythmic muscle movements occur in the fetus, which are also training and imitate breathing. The glottis is tightly closed, so amniotic fluid is not able to penetrate to the respiratory organs.

The kidneys begin to function in the fetus, urine in them is collected in small portions and exits through the urethra, entering the amniotic fluid.

At the twelfth week, the formation of the placenta is completed, which becomes able to function independently. The placenta is the most important organ for the fetus; through it, not only is the exchange of nutrients between the woman and the fetus. The placenta is an effective protector against internal and external toxins. nine0005

Twelfth week for the expectant mother

Twelve weeks is rightly considered the best in pregnancy. The woman's well-being returns to normal due to the transfer of control of the process from the corpus luteum, which produced progesterone, which is the culprit of many troubles, to the placenta. All manifestations of toxicosis disappear, women become relaxed and calm.

At this stage, the uterus has already enlarged enough and reached the edge of the pubis, but this is not able to affect the shape of the abdomen. nine0005

As a rule, the first trimester is not accompanied by weight gain. If toxicosis manifested itself to a large extent, even weight loss is possible. If a woman's appetite has not changed as a result of pregnancy, she should gain no more than 10% of her total weight during the entire pregnancy. Such an increase is usually 1-2 kg.

From the twelfth week, if the woman is doing well and there are no contraindications, it is recommended to start playing sports. At earlier periods, they are not dangerous, but most often experts recommend that women take care of themselves after the end of the first trimester. nine0005

Dance, yoga, swimming, fitness, and any other type of activity that has been designed specifically for pregnant women are perfect for the expectant mother. Before starting training, be sure to consult a doctor. If you choose the right load, classes will have a positive impact on the course of not only pregnancy, but also childbirth. Also, sports at this stage will contribute to a faster recovery after childbirth.

Second trimester of pregnancy (13 to 28 weeks)

The beginning of the second trimester is traditionally considered one of the calmest. Walk more. Walking is very helpful. Sit down to rest only when you are tired. Movement in the fresh air improves the supply of oxygen to the fetus, which is very necessary for its normal development.

Nausea disappears, appetite improves. Do not eat a lot of salty, refuse marinades, smoked meats, if you have not done this before. The increased need of the child's body for proteins and vitamins begins. The daily diet should include meat or fish (boiled or stewed), dairy products, especially cottage cheese, eggs. Do not forget about vegetables, fruits, greens. An excellent source of vitamin C is sauerkraut (rather than salted) cabbage. Salads from carrots, cabbage, beets, apples, green radish should be on your table every day. nine0005

At 17-20 weeks you will feel your baby's first kicks. From them you can determine how comfortable the baby feels. Intense tremors are a signal of lack of oxygen. Maybe you haven’t walked for a long time or, on the contrary, you are engaged in hard physical labor. Get out into the fresh air or lie down to rest and you will immediately feel how the child has calmed down.

But the lack of movement is an alarm. See a doctor immediately!

The need for calcium in the fetus increases sharply - an intensive growth of the skeleton has begun. If you don't have enough free calcium in your body right now, you could lose your teeth. To prevent this from happening, start taking calcium supplements in consultation with your doctor. nine0005

At this time, toxicosis of the second half of pregnancy may occur, the child suffers greatly from it. Therefore, if the doctor suggests hospitalization, do not refuse. Toxicosis can, if not be avoided, then at least reduce its manifestations. Be sure to follow your diet. Completely exclude salty, smoked, fried, spicy, canned food, chocolate. Do not eat a lot of grapes and drink fresh milk. Limit flour and rich products. As before, your diet should include boiled meat and fish, oatmeal and buckwheat porridge, vegetables and fruits

Periodically, once a week, check for fluid retention in the body. It is allowed to release liquid 200-300 ml less than what was drunk. If little urine is released, this is a signal of latent edema and the onset of toxicosis.

It is very good if you can measure your blood pressure at home. Show the results of measurements at the next visit to the doctor.

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