Changes in the first trimester of pregnancy

The First Trimester | Johns Hopkins Medicine

What You Need to Know

At your first prenatal visit, you will undergo a physical exam as well as certain tests and screenings to assess the health of you and your unborn baby.
First trimester symptoms vary from woman to woman, with some experiencing all known symptoms and others only a few. Duration of symptoms can vary as well.
After eight weeks, the embryo is referred to as a fetus.
Although the fetus is only 1 to 1.5 inches long at this point, all major organs and systems have been formed.
During the first trimester, the fetus is most susceptible to damage from substances, like alcohol, drugs and certain medicines, and illnesses, like rubella (German measles).

Your First Prenatal Visit

Your first prenatal visit is the most thorough. A complete medical history is taken, a physical exam is done, and certain tests and procedures are performed to assess the health of both you and your unborn baby. Your first prenatal visit may include:

Personal medical history. This may include taking record of any of the following:
- Previous and current medical conditions, like diabetes, high blood pressure (hypertension), anemia and/or allergies
- Current medicines (prescription, over-the-counter and nutritional supplements)
- Previous surgeries
Maternal and paternal family medical history, including illnesses, intellectual or developmental disabilities, and genetic disorders, like sickle cell disease or Tay-Sachs disease
Personal gynecological and obstetrical history, including past pregnancies (stillbirths, miscarriages, deliveries, terminations) and menstrual history (length and duration of menstrual periods)
Education, including a discussion regarding the importance of proper nutrition and expected weight gain in pregnancy; regular exercise; the avoidance of alcohol, drugs and tobacco during pregnancy; and a discussion of any concerns about domestic violence
Pelvic exam. This exam may be done for one or all of the following reasons:
- To note the size and position of the uterus
- To determine the age of the fetus
- To check the pelvic bone size and structure
- To perform a Pap test (also called Pap smear) to find the presence of abnormal cells
Lab tests, including the following:
- Urine tests. These are done to screen for bacteria, glucose and protein.
- Blood tests. These are done to determine your blood type.
  - All pregnant women are tested for the Rh factor during the early weeks of pregnancy. Rh incompatibility happens when the mother’s blood is Rh-negative, the father’s blood is Rh-positive and the fetus’ blood is Rh-positive. The mother may make antibodies against the Rh-positive fetus, which may lead to anemia in the fetus. Incompatibility problems are watched and appropriate medical treatment is available to prevent the formation of Rh antibodies during pregnancy. There are also other blood antibodies that may cause problems in pregnancy that are screened for on the first visit.
Blood screening tests. These are done to find diseases that could have an effect on the pregnancy. One example is rubella, an infectious disease that is also called German measles.
Genetic tests. These are done to find inherited diseases, like sickle cell disease and Tay-Sachs disease.
Other screening tests. These are performed to find infectious diseases, like sexually transmitted diseases and urinary tract infections.

The first prenatal visit is also an opportunity to ask any questions or discuss any concerns that you may have about your pregnancy.

The First Trimester: What to Expect

A healthy first trimester is crucial to the normal development of the fetus. You may not be showing much on the outside yet, but on the inside, all of the major body organs and systems of the fetus are forming.

As the embryo implants itself into the uterine wall, several developments take place, including the formation of the:

Amniotic sac. A sac filled with amniotic fluid, called the amniotic sac, surrounds the fetus throughout the pregnancy. The amniotic fluid is liquid made by the fetus and the amnion (the membrane that covers the fetal side of the placenta) that protects the fetus from injury. It also helps to regulate the temperature of the fetus.
Placenta. The placenta is an organ shaped like a flat cake that only grows during pregnancy. It attaches to the uterine wall with tiny projections called villi. Fetal blood vessels grow from the umbilical cord into these villi, exchanging nourishment and waste products with your blood. The fetal blood vessels are separated from your blood supply by a thin membrane.
Umbilical cord. The umbilical cord is a ropelike cord connecting the fetus to the placenta. The umbilical cord contains two arteries and a vein, which carry oxygen and nutrients to the fetus and waste products away from the fetus.

It is during this first trimester that the fetus is most susceptible to damage from substances, like alcohol, drugs and certain medicines, and illnesses, like rubella (German measles).

During the first trimester, your body and your baby’s body are changing rapidly.

Johns Hopkins Hospital Designated as Baby-Friendly

The Baby-Friendly Hospital Initiative, a global program launched by the World Health Organization and the United Nations Children’s Fund, has designated The Johns Hopkins Hospital as Baby-Friendly. This designation is given to hospitals and birthing centers that offer an optimal level of care for infant feeding and mother-baby bonding.

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The First Trimester: Changes to Your Body

During pregnancy, many changes will happen to your body to help nourish and protect your baby. Women experience these changes differently. Some symptoms of pregnancy continue for several weeks or months. Others are only experienced for a short time. Some women experience many symptoms, and other women experience only a few or none at all. The following is a list of changes and symptoms that may happen during the first trimester:

The mammary glands enlarge, causing the breasts to swell and become tender in preparation for breast-feeding. This is due to an increased amount of the hormones estrogen and progesterone. A supportive bra should be worn.
Your areolas (the pigmented areas around each breast’s nipple) will enlarge and darken. They may become covered with small, white bumps called Montgomery’s tubercles (enlarged sweat glands).
Veins become more noticeable on the surface of your breasts.
The uterus is growing and begins to press on your bladder. This causes you to need to urinate more often.
Partly due to surges in hormones, you may experience mood swings similar to premenstrual syndrome, a condition experienced by some women that is characterized by mood swings, irritability and other physical symptoms that happen shortly before each menstrual period.
Increased levels of hormones to sustain the pregnancy may cause “morning sickness,” which causes nausea and sometimes vomiting. However, morning sickness does not necessarily happen just in the morning and rarely interferes with proper nutrition for the mother and her fetus.
Constipation may happen as the growing uterus presses on the rectum and intestines.
The muscular contractions in the intestines, which help to move food through the digestive tract, are slowed due to high levels of progesterone. This may, in turn, cause heartburn, indigestion, constipation and gas.
Clothes may feel tighter around the breasts and waist, as the size of the stomach begins to increase to accommodate the growing fetus.
You may experience extreme tiredness due to the physical and emotional demands of pregnancy.
Cardiac volume increases by about 40 to 50 percent from the beginning to the end of the pregnancy. This causes an increased cardiac output. An increased cardiac output may cause an increased pulse rate during pregnancy. The increase in blood volume is needed for extra blood flow to the uterus.

The First Trimester: Fetal Development

The most dramatic changes and development happen during the first trimester. During the first eight weeks, a fetus is called an embryo. The embryo develops rapidly and by the end of the first trimester, it becomes a fetus that is fully formed, weighing approximately 0.5 to 1 ounce and measuring, on average, 3 to 4 inches in length.

First Trimester Fetal Growth and Development Benchmarks

The chart below provides benchmarks for most normal pregnancies. However, each fetus develops differently.

Timing	Development Benchmark
By the end of four weeks	All major systems and organs begin to form. The embryo looks like a tadpole. The neural tube (which becomes the brain and spinal cord), the digestive system, and the heart and circulatory system begin to form. The beginnings of the eyes and ears are developing. Tiny limb buds appear, which will develop into arms and legs. The heart is beating.
By the end of eight weeks	All major body systems continue to develop and function, including the circulatory, nervous, digestive, and urinary systems. The embryo is taking on a human shape, although the head is larger in proportion to the rest of the body. The mouth is developing tooth buds, which will become baby teeth. The eyes, nose, mouth, and ears are becoming more distinct. The arms and legs can be easily seen. The fingers and toes are still webbed, but can be clearly distinguished. The main organs continue to develop and you can hear the baby's heartbeat using an instrument called a Doppler. The bones begin to develop and the nose and jaws are rapidly developing. The embryo is in constant motion but cannot be felt by the mother.
From embryo to fetus	After 8 weeks, the embryo is now referred to as a fetus, which means offspring. Although the fetus is only 1 to 1.5 inches long at this point, all major organs and systems have been formed.
During weeks nine to 12	The external genital organs are developed. Fingernails and toenails appear. Eyelids are formed. Fetal movement increases. The arms and legs are fully formed. The voice box (larynx) begins to form in the trachea.

The fetus is most vulnerable during the first 12 weeks. During this period of time, all of the major organs and body systems are forming and can be damaged if the fetus is exposed to drugs, infectious agents, radiation, certain medications, tobacco and toxic substances.

Even though the organs and body systems are fully formed by the end of 12 weeks, the fetus cannot survive independently.

Changes in Your Body During Pregnancy: First Trimester

Path to well being

How do I know I’m pregnant?

A missed period is often the first sign of pregnancy. You may have some other physical signs as well. These include mild cramping and a little bleeding when the fertilized egg implants itself in your uterus.

If you’ve missed your period and think you may be pregnant, you can take a home pregnancy test. These tests are very accurate if you take them a few days after you expected to get your period. Call your doctor if the test is positive.

Why do I feel so tired?

Feeling very tired is another common symptom of early pregnancy. Your body is working hard to adjust to all the new physical changes. This can cause extreme fatigue. You may need to sleep longer than usual at night. If possible, you can take short naps during the day. Your energy will most likely return in the second trimester of pregnancy.

What is morning sickness?

Morning sickness consists of nausea and vomiting. It is caused by pregnancy hormones. Many pregnant people have it to some degree in their first trimester. Despite what it sounds, morning sickness can occur at any time of day. Certain foods or smells might make you feel sick and sometimes vomit. Some people seem to feel sicker when their stomachs are empty. Morning sickness usually goes away by the second trimester.

There are over-the-counter vitamins and herbal supplements that may help with morning sickness. Taking vitamin B6 may help with nausea, even though it may not prevent vomiting. Ginger supplements also may relieve nausea.

What other changes can I expect during the first trimester?

Frequent urination. Towards the end of the first trimester, you will feel like urinating more often. This is because your growing uterus pushes on your bladder. You may even leak a little urine when you cough or sneeze.

Lightheadedness. Your body is working overtime to make extra blood to support your baby. This can cause you to feel dizzy or lightheaded. Hunger, weakness, or stress can cause these symptoms as well.

Heartburn. The muscles that break down food become more relaxed during pregnancy. Hormone changes also slow down this process. Food also stays in your stomach longer to give your body more time to absorb nutrients. All these things can cause or worsen heartburn.

Constipation. You should be taking a daily prenatal vitamin that contains iron. The iron in the vitamin can lead to constipation. The slow process of breaking down food also can cause constipation, gas, and bloating. Your doctor may suggest taking fiber supplements or a stool softener to provide relief. Make sure you drink plenty of water (about eight glasses per day). Tell your doctor if you have severe problems. They may switch you to a different prenatal vitamin.

Visible veins. Your body makes extra blood and your heart pumps faster to meet the needs of pregnancy. This can cause the blue veins in your belly, breasts, and legs to become more noticeable. You may develop spider veins on your face, neck, or arms. These are tiny blood vessels that branch out from a central area, like the legs of a spider.

Skin changes. You may notice that your skin looks more rosy and shiny. Some people call this a “pregnancy glow.” It is caused by increased blood circulation. Pregnancy hormones can cause extra oil on your skin. It may cause you to have flares of acne.

Breast changes. Most people notice changes in their breasts early in pregnancy. The hormones in your body change to prepare for breastfeeding. As this occurs, your breasts may feel tender and swollen. You might notice small bumps forming in the area around your nipples. Your breasts will continue to grow and change throughout your pregnancy. They may feel even bigger and fuller later on.

Vaginal changes. The lining of your vagina will become thicker and less sensitive. You may notice a thin, white discharge. This is normal during pregnancy. Mild vaginal bleeding (spotting) is also normal and common. However, you should call your doctor if you have vaginal bleeding. If the bleeding is heavy or painful, go to the emergency room.

A growing belly. Your waistline will begin to expand as your baby and uterus grow larger. Depending on your size before pregnancy, you may not notice this change until the second trimester. It is normal to gain no or little weight in your first trimester.

Emotional symptoms. Your hormones are on overload during pregnancy. You might feel moody, forgetful, or unable to focus. Fatigue and stress can increase these symptoms.

Things to consider

Keep in mind that each pregnancy experience is unique. Even the same person may have different changes in their multiple pregnancies. For each change, your symptoms may be mild or severe. Do not worry if the changes do not happen at a certain time. Talk to your doctor if you have any concerns.

When to see your doctor

Contact your doctor if you think or know you are pregnant. They will make an appointment to confirm your pregnancy and talk to you about prenatal care.

You should also contact your doctor if your morning sickness and vomiting are severe enough to cause weight loss.

Questions to ask your doctor

Am I pregnant?
How far along am I in my pregnancy?
What kinds of physical and emotional changes should I expect?
Are my symptoms normal?
Are there any risks that I should be aware of?
Which prenatal vitamin do you recommend I take?

Resources

American Academy of Family Physicians: Taking Care of You and Your Baby While You’re Pregnant

1st trimester of pregnancy: what happens to the fetus

1st trimester of pregnancy: what happens to the fetus - Private maternity hospital Ekaterininskaya Clinics

1st trimester: 1st-12th weeks

The gestational age is calculated from the first day of the last menstruation, since it is difficult to determine the exact day of conception. Since conception usually occurs in the middle of the menstrual cycle, you are not actually pregnant during the first two weeks, but this period is counted as the beginning of pregnancy.

As soon as the fertilization of the egg takes place around the 3rd week, the hormones begin to produce changes in your body little by little. As a result, you may experience some of the following symptoms:

Morning sickness. As a result of rising levels of hormones characteristic of pregnancy, up to 80% of women in the 1st trimester experience morning sickness with symptoms such as nausea and vomiting. The idea that such malaise is observed only in the morning is a common misconception. In fact, symptoms can appear at any time of the day or night. Up to 1 in 5 women experience morning sickness in the 2nd trimester of pregnancy and can sometimes persist throughout pregnancy.
If you experience morning sickness, avoid foods that make you sick, eat little and often, avoid fatty and spicy foods, drink more water. If you experience severe symptoms or symptoms that bother you, see your doctor.
Breast changes. The mammary glands will begin to increase in size, soreness may appear. The nipples will increase in size, become darker and more protruding.
Fatigue. High levels of the hormone progesterone can make you feel tired and sleepy. Rest as often as possible in a horizontal position with your legs up and eat as well as possible, which is not easy if you are experiencing morning sickness!
Increased emotionality. A higher level of emotionality, manifested as a result of an increase in hormone levels, is normal. Understanding and patience on the part of your partner and loved ones is very important here.
Food likes and dislikes. You may find yourself intolerant of one food and addicted to another. This is usually not a problem, unless you feel like eating weird foods like chalk. If you are concerned about the situation, contact your doctor.
Frequent urination. As your fluid levels increase and your uterus puts pressure on your bladder, you will become more likely to visit the toilet. Go to the toilet as soon as you feel the need - this minimizes the pressure on the bladder.
Feeling of dizziness. Sometimes you may feel a little dizzy (this is due to hormonal changes). Try not to stay on your feet for a long time and slowly rise from a sitting or lying position. If you experience severe dizziness, contact your doctor immediately.
Heartburn and constipation. Your digestive system will slow down to give you more time to digest your food. This can lead to heartburn and constipation. To help manage heartburn, try to eat small meals at regular intervals and avoid fried or spicy foods and carbonated drinks. Constipation is helped by eating a diet rich in fiber, maintaining physical activity and drinking plenty of water.

1st trimester milestones

Approximately 7 days after fertilization, the embryo implants in the uterine wall. The placenta, umbilical cord and amniotic sac will begin to form to provide nourishment and protection to the embryo.
By the end of the first 12 weeks of pregnancy, the uterus is palpable through the wall of the abdomen, the abdomen will begin to grow.

Child development in the 1st trimester of pregnancy

By the end of the 1st trimester:

All the main organs of the baby are formed, the circulatory system works.
The development of the sexual organs has begun.
Fingers are formed on the hands and feet, nails have appeared.
Facial features have formed.
The length of the baby's body is about 6 cm from the head to the lower part of the body, he is already recognizable. The baby moves in the amniotic sac, but you don't feel it move yet.

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Physiological changes in the body during pregnancy

From the very first days of pregnancy, a woman's body undergoes profound transformations. These transformations are the result of the coordinated work of almost all body systems, as well as the result of the interaction of the mother's body with the child's body. During pregnancy, many internal organs undergo significant restructuring. These changes are adaptive in nature, and, in most cases, are short-lived and completely disappear after childbirth. Consider the changes in the basic systems of the vital activity of a woman's body during pregnancy.

The respiratory system during pregnancy works hard. The respiratory rate increases. This is due to an increase in the need of the mother and fetus for oxygen, as well as in the limitation of the respiratory movements of the diaphragm due to an increase in the size of the uterus, which occupies a significant space of the abdominal cavity.

The mother's cardiovascular system during pregnancy is forced to pump more blood to ensure an adequate supply of nutrients and oxygen to the fetus. In this regard, during pregnancy, the thickness and strength of the heart muscles increase, the pulse and the amount of blood pumped by the heart in one minute increase. In addition, the volume of circulating blood increases. In some cases, blood pressure increases. The tone of blood vessels during pregnancy decreases, which creates favorable conditions for increased supply of tissues with nutrients and oxygen. During pregnancy, the network of vessels of the uterus, vagina, and mammary glands decreases sharply. On the external genitalia, in the vagina, lower extremities, there is often an expansion of the veins, sometimes the formation of varicose veins. Heart rate decreases in the second half of pregnancy. It is generally accepted that the rise in blood pressure over 120-130 and a decrease to 100 mm Hg. signal the occurrence of pregnancy complications. But it is important to have data on the initial level of blood pressure.

And changes in the blood system. During pregnancy, blood formation increases, the number of red blood cells, hemoglobin, plasma and bcc increases. BCC by the end of pregnancy increases by 30-40%, and erythrocytes by 15-20%. Many healthy pregnant women have a slight leukocytosis. ESR during pregnancy increases to 30-40. Changes occur in the coagulation system that contribute to hemostasis and prevent significant blood loss during childbirth or placental abruption and in the early postpartum period.

Kidneys work hard during pregnancy. They secrete decay products of substances from the body of the mother and fetus (the waste products of the fetus pass through the placenta into the mother's blood).

Changes of the digestive system are represented by increased appetite (in most cases), craving for salty and sour foods. In some cases, there is an aversion to certain foods or dishes that were well tolerated before the onset of pregnancy. Due to the increased tone of the vagus nerve, constipation may occur.

The most significant changes, however, occur in genitals of pregnant women. These changes prepare the woman's reproductive system for childbirth and breastfeeding.

The uterus of a pregnant woman increases significantly in size. Its mass increases from 50 g - at the beginning of pregnancy to 1200 g - at the end of pregnancy. The volume of the uterine cavity by the end of pregnancy increases by more than 500 times! The blood supply to the uterus is greatly increased. In the walls of the uterus, the number of muscle fibers increases. The cervix is filled with thick mucus that clogs the cavity of the cervical canal. The fallopian tubes and ovaries also increase in size. In one of the ovaries, there is a "corpus luteum of pregnancy" - a place for the synthesis of hormones that support pregnancy. Walls vaginas will loosen and become more elastic. External genitalia (labia minor and major), also increase in size and become more elastic. The tissues of the perineum are loosened. In addition, there is an increase in mobility in the joints of the pelvis and a divergence of the pubic bones. The changes in the genital tract described above are of extremely important physiological significance for childbirth. Loosening the walls, increasing the mobility and elasticity of the genital tract increases their throughput and facilitates the movement of the fetus through them during childbirth.

Skin in the genital area and in the midline of the abdomen usually becomes darker in color. Sometimes "stretch marks" form on the skin of the lateral parts of the abdomen, which turn into whitish stripes after childbirth.

Mammary glands increase in size, become more elastic, tense. When pressing on the nipple, colostrum (first milk) is released.

Changes of the bone skeleton and muscular system . An increase in the concentration of the hormones relaxin and progesterone in the blood contributes to the leaching of calcium from the skeletal system. This helps to reduce the rigidity of the joints between the bones of the pelvis and increase the elasticity of the pelvic ring. Increasing the elasticity of the pelvis is of great importance in increasing the diameter of the internal bone ring in the first stage of labor and further reducing the resistance of the birth tract to fetal movement in the second stage of labor. Also, calcium, washed out of the mother's skeletal system, is used to build the skeleton of the fetus.

It should be noted that calcium compounds are washed out of all maternal bones (including the bones of the foot and spine). As shown earlier, a woman's weight increases during pregnancy by 10 -12 kg. This additional load against the background of a decrease in bone stiffness can cause foot deformity and the development of flat feet. A shift in the center of gravity of the body of a pregnant woman due to an increase in the weight of the uterus can lead to a change in the curvature of the spine and the appearance of pain in the back and pelvic bones. Therefore, for the prevention of flat feet, pregnant women are advised to wear comfortable shoes with low heels. It is advisable to use insoles that support the arch of the foot. For the prevention of back pain, special physical exercises are recommended that can unload the spine and sacrum, as well as wearing a comfortable bandage. Despite an increase in calcium loss by the bones of the skeleton of a pregnant woman and an increase in their elasticity, structure and bone density (as is the case with osteoporosis in older women).