3 Weeks Pregnant - What Happens? Sensations, Fetal Size

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Video: 3 Weeks Pregnant - What Happens? Sensations, Fetal Size

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Video: 3 Weeks Pregnant - What to Expect Your 3rd Week of Pregnancy 2023, January
3 Weeks Pregnant - What Happens? Sensations, Fetal Size
3 Weeks Pregnant - What Happens? Sensations, Fetal Size

3 weeks pregnant

Depending on which method is used to calculate the gestational age, the third week of the gestational period has different signs. According to the obstetric method, when the doctor counts the period from the beginning of the last menstruation, the fertilization of the egg takes place in the third week. It contains a complete chromosome set and is capable of rapid division.

According to the embryonic method, when the period is counted from the day of fertilization of the egg, it has already begun intensive division, and the delay in menstruation is 6-8 days.


  • What happens at 3 weeks in the female body?
  • Histogenesis according to the embryonic approach
  • What does a fetus look like at 3 weeks of gestation
  • Visible changes on ultrasound
  • Woman's sensations and visual signs
  • Role of hCG and progesterone in maintaining pregnancy
  • Pain in the abdomen and lower back
  • Toxicosis at 3 weeks
  • Sexual relationship
  • Is menstruation possible at 3 weeks of gestation?
  • Miscarriage at 3 weeks
  • Ectopic pregnancy
  • Frozen pregnancy
  • The temperature is increased - the norm and deviations
  • Formation of the diet from the 3rd week of pregnancy

What happens at 3 weeks in the female body?

If fertilization did not occur in the second obstetric week, it is carried out during this time period. The unique composition of chromosomes determines the sex of the unborn child, its characteristic features: the type of the nervous system, character, physique, height, eye and hair color and many other signs that make a person a unique creature.

Immediately after fertilization, the egg (now called the zygote) begins to divide. Simultaneously with the process of division, it moves along the fallopian tubes into the uterine cavity. Under the influence of hormones, the endometrium of the uterus is in such a state in which the implantation of the zygote is carried out with a high probability.

The implanted zygote is called a blastocyst, its cells are intensively and continuously dividing. After a short time, a cavity with an embryonic disc inside is formed in the blastocyst. At the end of 3 weeks of obstetric time, the disc is transformed into a cylinder with uneven ends. At one end of this formation, the head of the embryo is formed, the other end is transformed into a tail. It can be considered that the beginning of the laying of the main organs and systems of the future fetus has been laid.

Embryo parameters at 3 weeks of obstetric gestation:

  • Weight - 2-3 micrograms;

  • Height - 0.15-0.2 mm;
  • The number of cells is about 250.

The process of fixing the future embryo in the uterine cavity takes about 40 hours. The blastocyst must produce a special immunopressor protein so that the woman's body does not perceive foreign cells as a threat. If the release of protein does not occur, the immune system will perceive the cells of the father of the unborn child as a dangerous element of the organism and will not allow the blastocyst to gain a foothold in the uterine cavity.

The blastocyst consists of the outer layer, from the cells of which the placenta, amniotic bladder and umbilical cord will form, and the inner layer, the basis for the formation of the embryo. The importance of this gestational age is difficult to overestimate. If, during the laying of the most important organs of the unborn child, a woman does not part with bad habits, takes medications, eats improperly, does not strive for the correct mode of work and rest, these circumstances can be fatal and affect the course of pregnancy.

Histogenesis according to the embryonic approach

Three weeks from conception according to the embryonic method is the time for the formation of tissues of the most important organs. 15-17 days after fertilization, histogenesis occurs - the development and differentiation of the germ layers. This process is influenced by endogenous, or internal factors, and exogenous - the external environment, the woman's lifestyle and the conditions of her existence. Histogenesis is considered a critical period in the development of the embryo.

Directions of tissue differentiation:

  • the formation of ectoderm - the formation of a neural tube (the basis for the brain and spinal cord), and cells of the future epidermis;
  • formation of mesoderm - the formation of tissues of future muscles, bones, cartilage, kidneys, liver and gonads, peritoneum, lung and heart tissues;
  • endoderm formation - the formation of the intestinal tube (the basis for the digestive tract).

The end of histogenesis falls on the twentieth day of the embryo's existence. On the 20-21 day of intrauterine development, the chord (axis of the spinal column) and the folds of the trunk are formed in the future fetus.

What does a fetus look like at 3 weeks of gestation


If you count the term according to the embryonic method, at this time the fetus is an ovoid formation, consisting of a yolk sac, chorion and amnion. On the 21st day of embryo development, a heartbeat can be recorded. The amniotic fluid, which has protective properties, collects around the unborn fetus. The placenta has not yet formed at this stage of pregnancy.

Its functions are temporarily performed by a primitively arranged circulatory system, these are:

  • Getting oxygen;
  • Delivery of nutrients to the embryo;

  • Excretion of waste products.

Only by the end of 3 weeks does the formation of the villi of the future placenta begin. A capillary grows through each villi, which is connected to the mother's circulatory system. With the end of this process, the placenta will take over the synthesis of the necessary hormones, nutrition, oxygen supply, excretion, and regulation of blood circulation. Before the formation of the placenta, the corpus luteum of the ovaries takes over hormonal support for pregnancy.

The formation of the placenta is stimulated by an increase in the concentration of estrogen and progesterone. For their production, as well as for protecting the fetus from rejection, for inhibiting the formation of new eggs, human choriogonadotropic hormone, or hCG, is responsible. Its amount in all biological fluids of a woman increases many times over. All pregnancy tests are based on the reaction of reagents to this hormone in the woman's urine. By the end of 3 weeks of gestation, measured by the embryonic method, the test will show a positive result. If this does not happen, it makes sense to conduct another test in 2-3 days.

Visible changes on ultrasound

Ultrasound examination at 3 weeks of embryonic term is performed using a transvaginal probe.

This method is more informative, it allows you to record the following changes:

  • Confirmation of uterine pregnancy - detects the site of embryo implantation;
  • Exclusion of ectopic pregnancy;
  • Exclusion of cystic drift - a disease in which instead of an embryo in the uterus, the number of bubbles grows;
  • Thickening of the endometrium, or its hyperplasia;
  • The embryo is in the form of a tiny white point in the cavity of the ovum;
  • High vascularization (increased blood supply) of the corpus luteum, sometimes defined as an ovarian cyst.

There is no significant increase and change in the structure of the uterus. The third week of pregnancy in obstetric terms does not make it possible to determine any significant changes on ultrasound. In case of problems with conception, an ultrasound scan is performed at 3 obstetric weeks to determine whether ovulation has occurred or not.

Woman's sensations and visual signs

At this stage of pregnancy, there is a significant hormonal change in the woman's body, changes in metabolism. These changes are due to the sensations experienced by the pregnant woman, changes in her appearance.

Signs of pregnancy at 3 weeks:

  • Lack of menstruation;
  • Change in attitude to various dishes, products, aversion to familiar and loved earlier, and the desire to eat something exotic;
  • Fatigue, drowsiness, mild depression - symptoms are caused by increased production of progesterone;
  • Soreness, increased sensitivity and symmetrical engorgement of the mammary glands;
  • Mood swings, alternation of tearfulness and irritability with a feeling of euphoria;
  • Heightened perception of smells, rejection of aromas of perfumery, meat broth, etc.;

  • Increased or no appetite;
  • Frequent urination
  • The appearance of constipation;
  • The appearance of mild pain in the lower back or lower abdomen;
  • Nausea, weakness;
  • Increase in basal temperature values ​​up to + 37 ° C;
  • The appearance of atypical secretions, they may have a small admixture of blood during the process of egg implantation.

All of the above symptoms are subjective and depend on the individual characteristics of a woman.

Role of hCG and progesterone in maintaining pregnancy

Progesterone is called the main pregnancy hormone. Its amount increases dramatically at 3 weeks. Before the formation of the placenta, it is produced by the corpus luteum of the ovaries. On average, at this stage of pregnancy, its content is 15 nmol / l

Progesterone functions:

  • Stimulation of the growth of the uterus;
  • Preservation of pregnancy due to relaxation of the myometrium of the uterus under the influence of the hormone;
  • Thickening of the endometrium, and, as a result, reliable embryo implantation;
  • Helps prepare the mammary glands for feeding the baby;
  • Participates in the formation of some organs in the embryo;
  • Softens the body's immune response to the invasion of a foreign protein;
  • The formation of subcutaneous fat, which helps to provide the fetus with the necessary substances.

Determination of the level of progesterone in the blood is performed in the laboratory. The analysis is done on an empty stomach, preliminarily limiting physical and mental stress, excluding the use of hormonal drugs.

HCG at 3 weeks of gestation is intensively produced, promoting the production of estrogen and progesterone. Its concentration in the blood is 2 times higher than in a woman's urine. Every 2-3 days during this period, the concentration of chorionogonadotropin in the body increases significantly.

Pain in the abdomen and lower back

Depending on the pain threshold of a woman, she feels pain of a different nature - from strong to pulling, barely perceptible.

Possible causes of pain at 3 weeks of gestation:

  • The release of the egg (ovulation) can be accompanied by pain of varying intensity;
  • Digestive tract disorders;
  • Cystitis, pyelonephritis;
  • Blastocyst implantation into the endometrium of the uterus;
  • Surgical pathology;

  • The threat of termination of pregnancy;
  • Ectopic pregnancy.

In any case, if pain occurs, you should find out its cause with the help of a doctor. The onset of hormonal changes in the body affects the osteo-ligamentous apparatus. The release of the hormone relaxin leads to lower back pain.

Toxicosis at 3 weeks

This condition appears in some women very early - at the 3rd week of pregnancy, determined by the embryonic method. Most often, it appears during the first pregnancy, lasts until the final formation of the placenta.

Possible cause of toxicosis:

  • Isolation of waste products of the embryo into the blood;
  • Genetic predisposition;
  • Changes in hormonal levels.

It is manifested by nausea, less often vomiting, intolerance to odors and foods, and disappears after breakfast. With debilitating vomiting, a woman is shown treatment in a hospital.

Measures to alleviate the condition of a woman:

  • Eat fractional, chilled food;
  • Eat high-calorie foods;
  • Avoid fatty foods;
  • Drink enough water;
  • Have breakfast without getting out of bed.

Sexual relationship

The third week of the obstetric method is the time of fertilization of the egg, so sex is emphasized. Having sexual intercourse 2-3 days after probable ovulation increases the likelihood of conception and improves the quality of sperm. Both a decrease in sex drive and an increase in it are variants of the norm.

During sex at the 3rd week of pregnancy, calculated according to the embryonic method, an infrequent sign of pregnancy may appear - severe pain in the vagina and on the external genitals. These sensations are short-term and quickly disappear.

With the appearance of bloody vaginal discharge, pain, with the threat of miscarriage, intimate relationships will have to be temporarily stopped. A complete contraindication to sexual contacts is an STD in a partner or bacterial infections in him.

Is menstruation possible at 3 weeks of gestation?

Normal vaginal discharge during this period is thick, dense, mucous, resembling egg white in consistency, without an unpleasant odor. Lack of menstruation is the main symptom of an onset pregnancy. After the implantation of an egg into the uterus, the production of eggs is stopped by hormones.

However, some women do not make enough progesterone and estrogen to inhibit menstruation. They have a discharge similar in quality to menstrual blood. In this case, you need to see a doctor to determine the cause of the atypical bleeding.

Other causes of bleeding at 3 weeks gestation:

  • Ectopic pregnancy, when the embryo develops in the fallopian tube

  • Brown spotting short-term discharge during implantation;
  • Cervical erosion;
  • The consequences of a gynecological examination or sexual contact - the discharge is insignificant, does not pose a danger;
  • A symptom of a frozen pregnancy.

If the bleeding is painful, accompanied by spasms, and the discharge contains tissue fragments, is atypical, it may be caused by a miscarriage.

Miscarriage at 3 weeks

The causes of miscarriage can be a woman's bad habits, the consequences of stress or extreme physical exertion. Most often, genetic disorders in the development of the embryo lead to miscarriage. There is a crude statement that in this way "nature gets rid of marriage." Women who are not planning to become pregnant may confuse miscarriage symptoms with regular menstruation.

Signs of a miscarriage:

  • Pain in the lower abdomen, accompanied by cramps;
  • Temperature increase;
  • Bright red or brownish vaginal discharge;
  • Duration of the process for several hours or days.

A miscarriage should be differentiated from an ectopic pregnancy, a condition that threatens a woman's life.

Ectopic pregnancy

The onset of an atypical pregnancy is characterized by the same symptoms as the onset of a normal pregnancy - increased breast tenderness, delayed menstruation, nausea, and frequent mood swings. Unlike a normally developing embryo, in this case, its implantation took place in a narrowed or deformed fallopian tube.

Causes of an ectopic pregnancy:

  • Inflammatory processes in the fallopian tubes due to complications of STDs (gonorrhea, trichomoniasis, chlamydia);
  • Hormonal disorders;
  • Adhesions after surgery in the abdominal or pelvic organs;
  • Age over 40-45 years (occurs 4 times more often);
  • The presence of a uterine spiral (occurs 1.5 times more often);
  • Smoking (occurs 3.5 times more often).

An ectopic pregnancy is characterized by pain in one half of the abdomen, brown or dark red vaginal discharge, pain during intercourse. The growing embryo sooner or later ruptures the fallopian tube. If urgent action is not taken, death is possible.

Pipe rupture signs:

  • Sharp pain, painful shock;
  • Increased bleeding;
  • Loss of consciousness;
  • Pale skin.

If at least one of these signs appears, you should seek emergency help.

Frozen pregnancy

For various reasons, pregnancy at 3 weeks may end spontaneously. Symptoms of this condition can be severe pain in the lower back and lower abdomen, high fever, and the appearance of bloody vaginal discharge. An empty fetal egg without an embryo is visualized on ultrasound. Since signs of pregnancy persist, it is not easy for a woman to suspect a frozen pregnancy. The woman has no menstruation, her breasts are enlarged, and her increased sensitivity remains. The only thing that does not fit into the picture of pregnancy is the disappearance of signs of toxicosis, which until recently was manifested by nausea and a change in taste preferences.

Causes of pregnancy fading:

  • Excessive physical or mental stress;
  • Prolonged exposure to ultraviolet rays;
  • Side effects of drugs;
  • Rhesus conflict;
  • Genetically determined pathologies of the future fetus;
  • Bad habits;
  • A large number of abortions in a woman's history.

The temperature is increased - the norm and deviations

A slight increase in the body temperature of a pregnant woman at 3 weeks to + 37.3 ° C is a sign of an accelerated metabolism and increased production of progesterone. If there are no signs of viral respiratory infections, there is no need to worry about this. After 3-4 weeks, this condition returns to normal.

An increase in temperature over + 37.8 ° C, the addition of chills, weakness, pain in various organs is a sign of an inflammatory process, ARVI, diseases of internal organs. Here the help of a doctor is required, since self-medication is dangerous for the health of the unborn child. Since the main organs of the fetus are laid at 3 weeks, its development may be damaged, or there may be a threat of miscarriage.

Formation of the diet from the 3rd week of pregnancy

Food often and in large quantities does not always provide the adequate nutrition that a pregnant woman needs. From 3 weeks, you need to carefully calculate the diet.

Nutrition rules:

  • Include in the diet a complete protein of lean meat, dairy products, fish, legumes;
  • To fortify the diet, use fresh vegetables and fruits more often;
  • Eat fractionally - up to 5 times a day;
  • Avoid foods with flavors and colors, artificial carbonated drinks;
  • Replace white flour baked goods with wholemeal bran bread;
  • To protect against attacks of toxicosis, always have apples, crackers, mineral water on hand.

If you avoid strong emotional upheavals, excessive stress, take vitamins, get rid of bad habits, then pregnancy will definitely end with the birth of a healthy child. To improve your well-being, you can go in for swimming, exercise.


The author of the article: Lapikova Valentina Vladimirovna | Gynecologist, reproductologist

Education: Diploma in Obstetrics and Gynecology received at the Russian State Medical University of the Federal Agency for Healthcare and Social Development (2010). In 2013 completed postgraduate studies at N.N. N.I. Pirogova.

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