Development in first trimester

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.

Learn more

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.

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.

Stages of Fetal Development - First Trimester

Stages of Fetal Development - First Trimester

One - 13 Weeks

1st trimester of pregnancy: what happens to the fetus

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.

• 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.

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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Pregnancy management, 1st trimester - basic studies.

It is necessary to register for pregnancy, as this allows timely diagnosis of:

1. Pathologies of fetal development;
2. Chronic medical conditions in the mother that may affect the course and outcome of pregnancy;
3. Acute pathologies in the mother during pregnancy, affecting the growth and development of the fetus and the health of the mother.

Pregnancy is a complex restructuring of the body, diseases in the mother are not always known if the examination before conception is not passed.

What happens to the body during the 1st trimester of pregnancy

1st trimester is counted from conception to 12 weeks of pregnancy.

The fertilization of the egg occurs directly in the abdominal cavity. After fertilization, the egg is in the abdominal cavity and is actively split into smaller cells and becomes like a raspberry or mulberry, such an embryo is called a morula. Then it is captured by the villi of the fallopian tubes and moves into the uterine cavity. On the 7th day, the embryo is attached to the wall of the uterus. The fetal egg begins to form, consisting of amniotic fluid and the yolk sac, from which the embryo will form. At 7-8 weeks, the fetal bladder and placenta form from the fetal egg. From 8 to 12 weeks, the placenta is finally formed (in the future it only develops), it becomes visible on ultrasound. At 12 weeks, the fetus looks like a full-fledged baby about 9 in size.cm, he has formed limbs, head and main internal organs.

Mother's changes. Ideally, a woman does not feel pregnancy in any way. The only sign is an increase in the mammary glands, due to the development of glandular tissue under the action of hormones. The stomach practically does not increase.

During pregnancy, many women experience so-called "toxicosis" - nausea and/or vomiting. This is due to an increase in the level of estrogen (in particular progesterone) and hCG (chronic gonadotropin). Moreover, these symptoms can complicate the life of a pregnant woman, not only in the morning, but at any time of the day. Sometimes nausea or vomiting may persist throughout pregnancy.

There is such a formidable complication as excessive (uncontrolled) vomiting of pregnant women, which leads to maternal dehydration, electrolyte imbalance, liver and kidney dysfunction and encephalopathy, requiring hospitalization and treatment in a hospital.

It is best to eat according to your appetite. Food should not cause negative reactions, eat in small portions, pay attention to what kind of food provokes nausea and try not to eat it for a while, listen to your body, usually a woman herself feels what she would like to eat. Do not forget that food should not only be desirable and tasty, but also healthy. It would be ideal to eat according to the Harvard Healthy Eating Plate method, when ½ of the volume of the plate is occupied by vegetables, ¼ proteins (including plant origin), ¼ complex carbohydrates (grains, potatoes, cereals, etc.).

Your body will also begin to change. And the first thing you will feel will be engorgement and an increase in the sensitivity of the mammary glands, the nipples will swell a little and increase in size. It is important to wear comfortable, comfortable underwear and clothing to minimize discomfort. Sometimes there is pain in the nipples, your gynecologist may recommend ointments for this case.

We all remember that a pregnant woman becomes more vulnerable, whiny and sometimes even capricious. It is also associated with rising estrogen levels and requires patience and understanding on the part of family and partner. A calm atmosphere at home and, if possible, at work is important. You can connect such relaxation methods as walking, listening to your favorite music, aromatherapy in the absence of reactions to smells. Think about what could bring back your balance and calmness?

The main pregnancy hormone, progesterone, causes fluid retention in the body. In parallel with this, the growing uterus squeezes the bladder and there are frequent urges to urinate. This is normal, it is important to plan your day so that you always have the opportunity to visit the toilet.

Progesterone also reduces the tone of blood vessels, which can lead to dizziness. You can minimize these discomforts by changing the position of the body smoothly, do not get up and do not sit down abruptly. Another reason for frequent dizziness can be a decrease in the level of magnesium in the blood, your doctor will help you figure it out.

Pregnant women often have an increased need for sleep, which is explained by the same action of hormones, as well as the need for additional rest for the body, because there is a lot of work to bear, give birth and then feed the baby.

Under the action of progesterone, the smooth muscles of the whole organism (uterus, intestines, blood vessels, bile ducts and pancreatic ducts, etc.) relax, the work of internal organs slows down, which in turn leads to constipation and heartburn. In addition to medication correction (prescribed by a doctor), fractional meals in small portions, foods rich in fiber (our favorite vegetables), sufficient fluid intake, feasible physical activity (exercise therapy, walking, swimming, yoga, Pilates, etc.) help

Unfortunately, sometimes pregnancy is overshadowed by pathology, let's talk about the most common problems of the first trimester of pregnancy.

The most common problems of the 1st trimester of pregnancy

Bleeding : due to lack of progesterone, there is a spasm and relaxation of the muscles of the uterus and, accordingly, detachment of the ovum and bleeding (in severe cases - miscarriage). Also, with hypothyroidism, there is a violation of the implantation of the fetal egg, which also leads to bleeding.

Thrombosis . During pregnancy, blood clotting increases (this is normal - the body is preparing for blood loss). To prevent thrombosis of the veins of the lower extremities, it is necessary to stop taking oral contraceptives 6 months before the start of pregnancy planning, and during the onset of pregnancy, maintain sufficient physical activity (long walks, swimming) and be observed by a doctor. If you experience pain, swelling, "cyanosis" in the lower extremities, you should immediately consult a doctor.

Developmental anomalies and genetic pathologies . In the 1st trimester, abnormalities in the development of the fetus most often develop and manifest, which can occur as a result of ionizing radiation, infectious diseases suffered during pregnancy (rubella, influenza, etc.), taking drugs prohibited during pregnancy (fluoroquinolones, macrolides, tetracyclines, tranquilizers , etc.), genetic pathologies and hereditary diseases.

Anemia . More often it happens due to iron deficiency, tk. the fetus consumes a huge amount of it, taking away iron stores from the mother, less often due to bleeding. B12 and folic deficiency anemias also occur, also associated with increased consumption and insufficient intake by the mother. Anemia is a dangerous chronic lack of oxygen, causing fetal growth retardation syndrome. In severe cases, it can lead to fetal death.

During pregnancy chronic diseases may worsen . This is due to the fact that the fertilized egg already carries a part of DNA alien to the mother. To prevent egg rejection, the mother's body suppresses its immunity throughout pregnancy, which affects the body as a whole. Therefore, all diseases not identified at the stage of preparation for pregnancy should be detected and cured. This applies mainly to infectious diseases. For example, exacerbation of chronic pyelonephritis, or herpes virus infection.

Also during pregnancy there is a sharp restructuring of the hormonal background , which, in turn, affects somatic (non-infectious) diseases. For example, due to thickening of bile and compression of the gallbladder by the uterus, chronic cholecystitis may be exacerbated. As the fetus develops, the islets of Langerhans (cells that produce insulin in the pancreas) sometimes don't develop fast enough and the baby begins to consume the mother's insulin. If the mother has diabetes or impaired glucose tolerance (including hidden ones), both the child and the mother lack insulin, which leads to tissue damage to both the child and the mother (early aging of the placenta, fetal growth retardation, premature birth, polyhydramnios, increased blood pressure in a pregnant woman, the formation of a large fetus, the risk of injury to a woman and a child during childbirth, and the most formidable complication is intrauterine fetal death).

In addition, the fetal liver does not yet function as a detoxification organ, and all the decay products produced by the child must be processed by the mother's liver. 2% of pregnant women develop benign cholestatic hepatosis of pregnancy - violation of the formation and outflow of bile, which causes: effects on cells and bile ducts

1st trimester tests

Compulsory tests

Urinalysis . Needed to assess kidney function and determine the risk of eclampsia, a dangerous condition that develops during pregnancy, as well as to exclude asymptomatic bacteriuria.

Complete blood count . It aims to detect anemia, the risk of thrombosis, and inflammatory reactions.

Blood biochemistry - assessment of liver and kidney function, detection of diabetes mellitus and impaired tolerance (immunity) to glucose.

Coagulogram - detection of pathology of blood coagulation - risk of thrombosis or bleeding.

Therapist – to exclude the pathology of the internal organs, which may prevent or complicate the normal course of pregnancy and the upcoming birth. Most often, diseases such as pyelonephritis, anemia, cholecystitis, gastritis, vegetative dystonia, arterial hypertension are determined.

ECG in the direction of the therapist - detection of pathology of the cardiovascular system. Indirect signs of pericarditis, enlargement of the left ventricle, blockade of the conduction system of the heart.

Examination by an ophthalmologist - to determine the pathology of the organs of vision, incl. assessment of the risk of retinal detachment during childbirth.

ENT - the presence of chronic foci of infection (chronic tonsillitis, pharyngitis, sinusitis) increases the risk of miscarriage in the 1st trimester of pregnancy and the development of rheumatic complications.

At the period of 11-14 weeks, the first ultrasound screening is carried out to detect abnormalities in the fetus.

Additional tests

When registering, all pregnant women determine the blood type and Rh factor. If the Rh factor is negative, antibodies to the Rh factor in the mother and the blood type, the Rh factor of the father of the child, are determined. Sometimes there is incompatibility in blood types, this can happen if a woman has group I, and a man has any other. Analyzes are carried out once a month, starting from the 8th week of pregnancy. All this is done in order to take the necessary measures in time to prevent hemolytic disease of the newborn.

Anemia is initially diagnosed using a complete blood count and determination of hemoglobin (Hb), mean red cell volume (MCV), and mean red cell hemoglobin (MCH). If there is a decrease or increase in these indicators, the level of ferritin, transferrin, iron, folic acid, B12 is additionally examined.

Sometimes a consultation with a gastroenterologist is necessary to correct gastrointestinal disorders .

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