4th week of pregnancy (1st trimester)

Tests and ultrasound

An ultrasound at 4 weeks of pregnancy can already please the expectant mother with good news. However, it is carried out at this time in very rare cases. Firstly, many pregnant women do not yet know that they will soon become mothers and simply do not think about any ultrasound, and secondly, some women believe that it is undesirable to conduct an ultrasound examination at such an early stage.

You can try to do a simple pregnancy test at home (rapid tests are made in the form of strips or other similar devices). But at 4 weeks you shouldn’t really trust such a test: despite the fact that the outer layer of the embryo has already begun to produce human chorionic gonadotropin (hCG), it is not yet enough for a home test. But a blood test for hCG often gives a positive result, since the content of this hormone in the blood is much higher.

What happens to the fetus at this stage?

According to the obstetric method, at 4 weeks the zygote, or fertilized egg, begins to rapidly divide. It produces many cells with different structures and functions. Actually, it is not yet a fruit. The collection of cells is called a morula, or blastocyst. In shape, it resembles a multi-chambered berry, not yet attached to the endometrium of the uterus. It is difficult to name the exact parameters of the blastocyst, since it is continuously growing.

Approximate parameters of the future embryo:

• Weight – 0.5 mg;
• Height – 0.36-1 g.

In figurative language, it is comparable in size to a poppy seed.

If we calculate the gestational age using the embryonic method, at week 4 the embryo has already established itself in the uterine cavity and continues intensive development.

At this stage, it is a germinal disc and consists of 3 layers:

• Primary ectoderm is the basis of skin, hair, tooth enamel, eye lenses, nervous system cells;
• Mesoderm is the basis for the formation of future organs, skeleton, muscle tissue, circulatory, excretory and reproductive systems;
• Endoderm is the basis of the respiratory and digestive systems, liver, thyroid and pancreas.

The future fetal head currently looks like a small droplet. The placenta has already begun to form. While it is still very primitive, it consists of 2 layers. The tissues of the future placenta are already connected to the tissues of the uterus, which makes it possible to provide the embryo with nutrition and oxygen.

The following extraembryonic organs are responsible for nutrition:

• The chorion is a prerequisite for the real placenta, which will form until the 12th week; from the 4th week, a vascular network begins to form at the point of contact of the embryo with the endometrium of the uterus;
• Amnion is a kind of “packaging” of the embryo, a prerequisite for the amniotic sac, which protects the fetus from physical impact and drying out;
• The yolk sac is a supply of nutrients for the embryo, the basis of hematopoiesis until 7-8 weeks of pregnancy.

Without the yolk sac, the existence of an embryo is impossible; if its functions are impaired or there is congenital pathology, a miscarriage occurs. When performing an ultrasound, the doctor determines the quality of pregnancy and the viability of the embryo based on the condition of the yolk sac.

According to research, it turned out that male genes are responsible for the formation of extra-embryonic organs. We can say that the function of protection and provision is inherent in a person even before birth.

By the end of 4 weeks, blastogenesis, the initial stage of embryonic development, ends.

Lifestyle, nutrition and vitamins

Week 4 is, as a rule, the last week when a woman cannot yet reliably know that pregnancy has occurred. If you were planning a child and did everything to conceive, lead a healthy lifestyle, give up alcohol, smoking, taking antibiotics, avoid contact with sick people, try to be calmer, picky about food and drinks. And don't forget about vitamins. But remember: only a doctor can give you a detailed answer to the question of what vitamins to take and in what quantity.

Condition of the uterus and endometrium

The size of the uterus at the 4th week of pregnancy practically does not increase; it is still located within the boundaries of the small pelvis. Its structure changes - the uterus becomes swollen, the tissues in the isthmus area soften, which gives it slight mobility. Both the uterus and its cervix become bluish due to the influx of blood. A mucous plug begins to form in the cervical canal, protecting the fetus from bacterial infection from the outside.

The endometrium thickens, its structure changes - new blood vessels sprout, the number of glandular cells increases, which subsequently transform into the placenta. At this stage, such changes ensure the viability of the embryo, its respiration and nutrition. Due to the large number of blood vessels, the endometrium becomes bluish in color. Its thickness at 4 weeks, calculated using the embryonic method, is about 2 cm.

Development of the embryo at 4 weeks of pregnancy

At this time, the germ layers - inner, middle and outer - begin to form. The cells of the inner leaf serve to form internal organs: liver, bladder, pancreas, lungs, respiratory and digestive systems. The middle leaf forms the skeleton, muscular system, cartilage, heart, kidneys, gonads, lymph and blood. The cells of the outer leaf are responsible for the skin, nails, tooth enamel, epithelial tissue of the ears, eyes, nose, and the nervous system.

During this period, the chorion, amnion and yolk sac also develop. Thanks to them, the embryo receives comprehensive protection and in the future will be provided with everything necessary for development. The chorion soon transforms into the placenta, the amnion into the fetal bladder. As for the yolk sac, this organ, which provides nutrition and respiration of the fetal egg, after 12-13 weeks of pregnancy will cease its functions, shrink and “retract” into the fetal cavity.

What develops in the fourth week of pregnancy

At the beginning of this week, the fetus begins to develop into an embryo. Outwardly, it resembles a flat, three-layer disk, each layer of which will become the basis for the formation of the child’s organs and systems.

Thus, the pancreas, digestive system, lungs, and liver appear from the inner layer. The middle layer forms the heart, blood vessels, kidneys, muscles, and skeleton. From the outer layer the eye lenses, hair, tooth enamel, nervous system, head, and skin develop.

The size of the fetus at the 4th week of pregnancy is 2 mm. Despite such microscopic dimensions, the embryo develops very rapidly. Extraembryonic organs appear (yolk sac, amnion, chorion), which are responsible for providing the fetus with breathing, nutrition, provide it with biochemical support and protect the child until the amnion forms the amniotic sac, and the chorion forms the placenta.

What awaits the expectant mother?

When pregnancy is already an established fact, the woman is registered. At 10-13 weeks, the expectant mother will have to undergo the first screening, consisting of a blood test and ultrasound. Screening is necessary in order to exclude many genetic pathologies of the fetus, as well as to check the health of the expectant mother.

The longer the period, the more often the woman will have to appear in the doctor’s office. From this moment on, the health of the expectant mother will be carefully monitored, however, the expectant mother must also take care of herself.

Condition of the expectant mother

If we can speak more or less accurately about the development of a child, since there are general norms and indicators, then the condition of all women during this period is different. Some people have already at this stage begun to experience toxicosis, an aversion to certain types of foods, while others feel great and, moreover, do not even know about the onset of pregnancy.

Signs of pregnancy at 4 weeks (embryonic period)

It is at this time that it becomes possible to talk about signs of pregnancy, since before this they appeared only in some, especially sensitive individuals. The main reasons for the manifestation of pregnancy are the beginning of an active restructuring of the entire body, its activation and a sharp change in hormonal levels.

Main symptoms of pregnancy:

• severe fatigue, rapid loss of strength, feeling of exhaustion;
• unreasonable apathy;
• persistent desire to sleep;
• an increase in the amount of saliva produced;
• a sharp improvement in the sense of smell;
• nausea in the morning as a result of certain smells, food;
• constant change of mood for no apparent reason;
• darkening of the labia;
• the appearance of pigment spots on the skin.

In some cases, already at the very beginning of pregnancy, a woman experiences constipation and a frequent desire to empty the bladder.

The week in question is noteworthy in that the woman already knows about the fertilization that has occurred. Thanks to the good news, the couple begins to prepare, some change their habits, others revise their work schedule, etc.

The delay in menstruation is already more than 3 weeks, so even without a pregnancy test, any girl must suspect an interesting condition.

Internal changes (in the uterus, formation of the placenta)

There are several global transformations at this stage:

• the beginning of progesterone production;
• rapid development of the placenta;
• appearance of amniotic sac and placenta.

The uterus gradually grows, at 4 weeks it reaches the size of a chicken egg, a large plum, but this does not affect the appearance in any way. At an appointment with a gynecologist, the doctor can already accurately determine the onset of pregnancy. Right now it is important to go to the antenatal clinic for registration and further monitoring.

Frequent urination is explained precisely by the enlargement of the uterus, and it is extremely undesirable to endure the urge now. If bowel movements are painless, there is nothing to worry about, but pain in the lumbar region may indicate the onset of cystitis - an unpleasant and quite dangerous disease of the genitourinary system during pregnancy.

An important event this week is the production of progesterone. It is thanks to him that the uterus stops contracting, does not become toned, and, therefore, prevents miscarriage.

At the 6th obstetric week, the placenta rapidly develops - the fundamental link between mother and baby, its source of nutrition and life for the coming months. Now the placenta should be firmly attached to the uterus, after which the concern for nutrition and oxygen delivery to the fetus will rest entirely with it. Until this moment, this function is performed by the yolk sac, which will cease to exist from the moment the placenta fully matures.

The amniotic sac, which is actively forming this week, serves as a safety cushion for the baby in the event of mechanical impact on the mother’s body. The rudiments of the umbilical cord appear, but for it to work fully it still needs to improve for a long time.

External changes of the expectant mother

The uterus continues to grow, but its size has not yet increased enough for external changes to occur. Waist circumference at this stage, as a rule, remains the same.

The only problem that can add extra sentiment to a still wasp waist is increased gas formation. With the onset of pregnancy, the intestines become lazy, they no longer perform their functions at the same speed, resulting in the formation of additional gases. Proper fractional nutrition will help minimize this nuisance.

Now the only thing that can tell others about your pregnancy is your breasts. It is she who undergoes the first changes due to hormonal changes.

Sensitive women report the following symptoms:

• slight breast swelling;
• increased sensitivity;
• areolas become noticeably darker;
• the skin around the nipple is itchy or tingling.

In the first weeks of pregnancy, breasts most often do not change in size, they simply become fuller and more vulnerable, which indicates preparation for lactation in the future. Some women note that the nipple itself also becomes larger.

While it is still possible to hide changes in the breasts from others, skin pigmentation, which often mars pregnancy at 4 weeks, is noticeable at first sight. Any hormonal changes are reflected in the skin, turning it loose and porous. Acne, sagging, unpleasant tint, and pigment spots appear.

During the first month of pregnancy, a woman’s weight, as a rule, does not change dramatically. Most often, 500 g is added. up to 1.5 kg. At the same time, girls with a thin physique tend to gain weight faster than women with a larger body.

Discharge: nature and quantity

Already from the first weeks of pregnancy, the genitals undergo changes under the influence of “raging” hormones. Due to the accumulation of a special substance - glycogen - in the vaginal mucosa, a large number of lactic acid bacteria appear. They change the surrounding microflora and activate the production of light-colored secretions.

The vaginal mucosa becomes more congested during this period. With adequate protective properties, a large release of lactic acid occurs, due to which pathogenic bacteria slow down their growth. Otherwise, it is possible to develop an unpleasant disease - colpitis. Leucorrhoea in large quantities may indicate its development.

When a woman notices that the discharge becomes cheesy, suspicion falls on another disease - candiosis. It is very common in pregnant women and is also known as “thrush”.

Signs of candiosis:

• strong light discharge with a structure reminiscent of cottage cheese;
• unpleasant itching sensations in the external genitalia;
• painful urination.

It is important to know that when pregnancy occurs, you must inform your doctor about any bleeding. Even a small amount, especially in combination with painful sensations, does not bode well. In most cases, these are symptoms of an incipient miscarriage. Only immediate hospitalization and taking the necessary measures make it possible to maintain the pregnancy.

Symptoms and signs of pregnancy: 4 weeks

Many women are able to accurately determine their condition from the first days of conception, especially if they became mothers. For others, pregnancy may be asymptomatic until the third month. Of course, the absence of menstruation is the most important sign, but it often makes itself felt, even if the embryo is already fully developing in the expectant mother’s belly.

However, it is during the fourth week of pregnancy that most women experience pronounced symptoms.

A pronounced symptom that conception has occurred is the manifestation of sensitivity of the mammary glands. They increase slightly in size, and dark circles form around the nipples.

Many women note the appearance of toxicosis, which is most often expressed in nausea and rejection of certain types of foods. Nausea usually occurs in the morning. The lower abdomen begins to feel tight, and the body temperature can rise to 37 degrees. A woman in the fourth week of pregnancy feels tired and sleepy, and her mood jumps all the time. Often expectant mothers become irritable and whiny, something is constantly bothering them. Such symptoms are also harbingers of menstruation, so it is not surprising that in the early stages women cannot yet determine pregnancy.

Despite the fact that the initial signs of pregnancy at 4 weeks are similar to perdmenstrual syndrome, the expectant mother can intuitively guess that a new life is developing in her. And she can confirm her guesses in four ways.

At this stage, the pregnancy test will already show you two stripes, but only if hCG is present in the urine in sufficient quantities. Almost everyone has heard the abbreviation hCG, but not many know what it really is and why this substance begins to be produced in the body of a woman expecting a child.

Human chorionic gonadotropin is a hormone secreted by the embryonic membrane, or chorion. It is necessary to ensure that the female genital organs are tuned in to bearing a fetus. HCG is necessary for the development of the corpus luteum in the early stages of pregnancy. It is especially important as an immunosuppressive substance that prevents the female body from rejecting the fetus. The longer the period, the greater the amount of hCG present in the urine and blood. Its level begins to decrease only in the tenth week.

A pregnancy test will only show two lines if the level of hCG in the mother's body is too high. Which test is preferable to purchase? Currently, inkjet and electronic tests are considered the best, but anyone can show pregnancy, since the algorithm of action is the same for everyone.

The most inexpensive and common are test strips. It is better to use them in the morning, when the level of hCG in the urine is highest.

In order for the test to show a reliable result, it must be used correctly. To do this, you need to find a container to collect urine. If the test is kept in liquid, it may show an incorrect result. The sensitivity of test strips is low.

In cassette versions, the strip with the reagent is located in a plastic cassette. To detect pregnancy, you need to place a few drops of urine in one window and wait until the result appears in the second window. It costs more than strips.

Some of the most reliable are inkjet options, which are both highly sensitive and more convenient to use.

The most modern are digital tests, in which “+” or “-” appear instead of stripes, but the operating principle is similar. The most expensive electronic options also show the gestational age.

And yet, if the level of hCG in the urine is low, the woman will not be able to detect the pregnancy status at 4 weeks.

In this case, it is necessary to donate blood for analysis. This is the most reliable way to detect pregnancy, since a woman expecting a child will definitely have hCG in her blood.

Pregnancy at 4 weeks can be confirmed almost accurately by a doctor. At this time, the uterus is already increasing in size and softening. The doctor determines the presence of an embryo by the blue color of the cervix. At this stage, a mucus plug has also already been formed, which will protect the internal organs from infections from the outside.

• Finally, the fourth way to find out about the fourth week of pregnancy is to undergo an ultrasound. But usually the doctor does not prescribe an ultrasound so early. A woman can undergo this analysis only if the doctor has doubts about the harmonious development of the fetus.

What should an expectant mother do when she is 4 weeks pregnant?

The early period is a very important time for the development of the embryo. Immediately after a woman finds out that she is expecting a baby, she should begin to take care of herself with redoubled force.

First, you need to make an appointment with a gynecologist, who will look at the condition of the genital organs and eliminate initial risks.

Secondly, you need to change your diet. It is important to take additional vitamins prescribed by your doctor. Why should this be done? Because the lack of one or another element in the process of laying internal organs can cause pathology. For example, a lack of folic acid can lead to impaired brain development. Folic acid is recommended to be used even before conception.

It is necessary to completely reconsider your lifestyle as soon as you find out that a fetus is actively developing in your stomach. Nutrition should become healthy. No alcohol or cigarettes - they should be excluded. Some women cannot give up bad habits, not even suspecting that half of the fetal pathologies are associated with smoking or drinking alcoholic beverages.

Interesting Facts

Your baby is the size of

poppy seed

0.36-1mm Size

0.5 g Weight

The fourth week of pregnancy is one tenth of your journey to motherhood. About 10 days ago, fertilization occurred, the embryo reached the uterus and attached to its wall. How is your body changing and what should you pay attention to during this period?

Note that we are talking about the obstetric calculation method. The picture is completely different at 4 weeks of pregnancy from conception. You can find out what happens to the fetus and the woman at this stage from the article “6th week of gestation.” The embryonic method is conventional and is not used by gynecologists, so our calendar is based on the obstetric counting system.

Possible problems

The fourth week is the first critical point of pregnancy: the woman’s further condition depends on how successfully the embryo is implanted. During this period, a number of dangerous conditions may arise.

Spontaneous interruption

If bleeding during menstruation is unusually heavy, and a woman complains that her lower abdomen is very tight, it may be a miscarriage. Fertilization occurred a little earlier than 4 weeks, but the embryo was unable to attach to the wall of the uterus. The cause may be infectious diseases, severe physical or emotional stress, pathologies of the uterus or fetus. Often, such bleeding at this time is perceived as normal menstruation.

Ectopic pregnancy

If the embryo remains in the fallopian tube or ovaries, then it is impossible to maintain the gestation. Pathology often occurs against the background of inflammatory processes and adhesions in the fallopian tubes, as well as with abnormal structure of the genital organs.

Infectious diseases

Primary infection with TORCH infections during pregnancy disrupts fetal development and leads to miscarriage. This can be avoided if you get the necessary vaccinations in advance, do not eat poorly cooked meat, do not have contact with cats, and do not visit crowded places.

Abdominal and lower back pain at 4 weeks

Low-intensity pain in the lower abdomen and lower back, without abnormal discharge and increased body temperature, is the norm at 4 weeks of pregnancy. Such sensations are caused by hormonal changes in the body; they pass quickly and without consequences. Intense pain accompanied by bloody discharge may be signs of the following pathologies:

• cystitis, pyelonephritis – urination disorders and hyperthermia are added;
• Constipation, flatulence;
• Ectopic pregnancy - sensations often occur on one side;
• Threatened miscarriage or frozen embryo - accompanied by bloody or sanguineous vaginal discharge;
• Surgical pathologies (appendicitis).

The appearance of such symptoms is a reason to immediately consult a doctor.