Which hormone is released from the placenta?

First trimester of pregnancy: time of development

What happens in the first trimester of pregnancy?

In the first trimester, as the first third of the 40-week pregnancy is called, a single cell - the zygote created by fertilization - transforms into an embryo. In these first twelve weeks of pregnancy, the embryo makes such a huge leap in development than at any other time in its further life. The mother-to-be's body is also going through dramatic changes as it adapts completely to the needs of pregnancy and the unborn child. The calculation of the length of pregnancy begins with the last menstrual period, although fertilization actually took place two weeks later.

When does the embryo become a fetus?

In some countries only the first eight, in other countries - including Germany - the first twelve weeks of pregnancy are referred to as the embryonic stage. The subsequent periods of development of the fruit of the abdomen then belong to the fetal stage. By the end of the second month, all important human organs and body systems are in place. By the end of the third month, the fetus has human features.

What happens in the first few weeks?

About two weeks after fertilization, the germinal vesicle is completely implanted in the uterus. Around the fourth week of pregnancy, the germinal vesicle begins to develop into the embryo that can just be seen with the naked eye. The outer layer of cells, the trophoblast, develops into a chorion, a membrane surrounding the germ, which ultimately transforms into placenta, the placenta. At around the same time, the inner cell structure forms a flat disc, the germinal disc, from which the embryo will later develop.

In the fifth week of pregnancy, the germinal disc forms three different cell layers, from which all body organs emerge in the following weeks. At the end of this week, the embryo is two millimeters long. It already has a sophisticated system of paired blood vessels.

What does the embryo look like in the sixth week?

At the beginning of this period, the embryo is about five millimeters long, has a head and neck and primitive eyes and ears. The heart beats and can be made visible via ultrasound, the embryonic circulation as well as digestive organs, liver and kidneys develop. In the seventh week the appendages for the nostrils, lips, tongue, teeth and jaw as well as the arm and leg buds are formed.

How big is the embryo at the eighth week?

The embryo now measures three centimeters and weighs about 2.7 grams and now has recognizable human features. Its head is about the size of its body. All important parts of the brain are present. The liver starts making blood cells. The eyes are visible through pigment deposits, but are still covered by a layer of skin that later develops into the eyelids. The ear systems are formed.

Arms and legs are present, but hands and feet are not yet differentiated. Fingers and toes begin to develop. Knee and elbow joints have also formed so that arms and legs can be bent. The ossification process has started, the muscles begin with spontaneous contractions and become stronger and stronger as a result.

What happens between the ninth and twelfth week?

All essential organs have been created. Now the body begins to grow in length. The legs continue to grow and the previously fused fingers separate. The auricle continues to develop, but the eyes remain tightly closed. The epidermis and dermis are recognizable and the bone marrow has started producing blood cells. The palate closes and smooth muscles develop in the internal organs. The sexual organs are formed. The heart pumps blood through the circulatory system and through the umbilical cord to the placenta. The fetus is now up to nine inches long and weighs about 30 grams.

How does the placenta form?

As soon as the egg cell nests in the lining of the uterus, so-called chorionic villi form from blood vessels in the chorion, the membrane surrounding the germ cell. These are washed by maternal blood from blood vessels in the deepest layer of the uterine lining. The maternal and child's circulation are always separate, but nutrients and oxygen from the maternal organism and waste products from the child's organism can cross the placental barrier. The blood passes through the umbilical cord, one vein of which brings the nutrient-rich blood from the mother to the fetus and two arteries of which bring the nutrient-poor blood from the fetus to the mother.

What additional tasks does the placenta take on?

It also serves as a nutrient store for proteins, iron and calcium and releases these substances to the fetus when required. The placenta also protects the unborn child from microorganisms. However, some viruses, such as chickenpox or rubella, can cross the placental barrier with the mother's blood and damage the unborn child. The placenta also offers little protection against certain drugs such as alcohol and nicotine, which can pass into the fetal circulation and impair the development of the unborn child.

How does the pregnant woman's body adapt?

In this early phase of pregnancy, the female body is attuned to the care of the unborn child and the impending birth. The changes affect almost all body systems.

Due to the general acceleration of the metabolism, hair and nails also grow faster. The hormone relaxin released by the placenta leads to a softening and stretching of the ligaments, the pelvis can expand and becomes more flexible.

The voluntary muscles also expand. At the same time, the muscle tone of the smooth muscles in the gastrointestinal tract, in the uterus and ureters is reduced under the action of progesterone, which is released by the placenta.

The increase in blood volume leads to an improvement in blood flow through the uterus and placenta, but also through the kidneys and lungs.

How does the uterus develop?

In the course of the first trimester, the uterus, which was originally the size of a fist, gradually enlarges into the pelvic cavity and changes its originally pear-like shape to that of a ball. The lining of the uterus becomes thicker. Due to the increased blood supply and the effect of estrogen, the cervix expands and becomes more supple. In the 13th week the uterus protrudes beyond the pelvic entrance and can be felt at the upper edge of the pubic symphysis.

How do the breasts change?

The increased blood supply causes the breasts to enlarge and become sensitive to touch. Their structure becomes uneven and superficial veins appear more prominent. Between the tenth and twelfth week of pregnancy, the openings in the sebum glands of the areolas (Montgomery glands) widen. Their sebum secretions make the nipples supple. In addition, the fatty tissue of the breasts is continuously replaced by a system of milk ducts.

Why do the metabolic processes accelerate?

The acceleration of all metabolic processes serves the optimal supply of child and maternal tissue during the whole pregnancy. The increased metabolism in early pregnancy causes a continuous increase in body weight by an average of two to three kilograms in the first trimester. From the first few weeks of pregnancy, the placenta produces the hormone HCS (human chorionic somatotropin). Along with estrogen and progesterone, HCS stimulates the growth and development of the mammary glands. HCT (human chorionic thyreotropin), another hormone produced in the placenta, increases energy expenditure by around 20 to 25 percent. For this reason, pregnant women sweat more than normal. The increased concentration of parathyroid hormone from the parathyroid glands also increases the blood concentration of vitamin D and calcium, so that both substances are available for bone formation in the fetus.

Did you know that …

the human being would be taller than the highest mountain on earth, would he continue to grow at the same speed after birth as in the womb?

at the beginning of embryonic development the arms are longer than the legs? It also fits that we first grasp and then learn to walk.

more than half of the germinal vesicles nested in the uterine lining do not lead to pregnancy? Most often, chromosomal abnormalities are the cause of their death.

Why is there no menstrual period?

After the fertilized egg cell has implanted, the lining of the uterus changes and, under the action of the now active hormones, develops into the ideal environment for the embryo. Menstruation is suppressed. Early in pregnancy, some women experience mild abdominal pain or symptoms similar to premenstrual syndrome. Sometimes period-like bleeding continues for the first two to three months despite an existing pregnancy. They are triggered by the insufficient secretion of progesterone, the concentration of which is not yet sufficient to completely interrupt the menstrual cycle. However, the bleeding is weaker and shorter than normal menstruation.

What are pregnancy symptoms caused by?

Fatigue, dizziness and exhaustion result from changes in hormonal status and from the low blood pressure in the first few months of pregnancy. Fatigue usually subsides in the second trimester, but can become more pronounced in the last trimester of pregnancy.

Nausea and vomiting, feelings of disgust with certain smells and foods are also caused by the hormonal changes. Up to 50 percent of all pregnant women suffer from these unpleasant side effects in the first trimester of pregnancy. The nausea can also be accompanied by a feeling of fullness and can be exacerbated by certain smells. Even if one often speaks of "morning sickness", it is by no means limited to the time after getting up, but can occur throughout the day. Vomiting is more common in multiple pregnancies. However, the symptoms usually subside after the twelfth week; only in rare cases do they persist throughout pregnancy.

What causes the urge to urinate more often?

The increased urge to void is likely caused by the pressure of the growing uterus on the bladder and increased blood flow to the bladder. During the fourth month of pregnancy, the frequency of the urge to urinate decreases somewhat, but can increase again in late pregnancy if the baby's head presses on the bladder before birth.

How does the skin change?

The increased release of MSH (melanocyte-stimulating hormone) by the pituitary gland affects skin pigmentation. This will make existing birthmarks and freckles darker. By the tenth to twelfth weeks, nipples and areolas change color from pink to brown. The sebum and sweat glands also increase their activity; latent or existing acne can worsen.

How do you avoid risks for the unborn child?

Hardly any woman lives in an environment that is perfectly adapted to the needs of the unborn child. But by following some precautionary measures, the existing risks can be reduced.

  • Avoid contact with dangerous substances, as well as with animals, during pregnancy; as well as physical exertion such as heavy lifting or climbing.
  • Water temperatures that are too high should be avoided when bathing, especially in the first trimester of pregnancy.
  • Eat healthy. Avoid pies, unpasteurized dairy products, undercooked meat, raw fish and raw eggs.
  • Over-the-counter drugs, including pain relievers, antacids (gastric acid-binding drugs), antihistamines (antiallergic agents) and antitussives (cough suppressants) should only be taken if clearly indicated and in consultation with a doctor.
  • Inform your doctor, dentist and radiologist about the pregnancy so that you will only be x-rayed in an extreme emergency and using a lower dose of radiation.
  • Avoid contact with people with febrile or infectious diseases, especially in the first trimester of pregnancy. Avoid staying in an environment where there is a lot of smoking.

What is behind the term ...

Tubal pregnancy? In "ectopic pregnancy" the fertilized egg cell implanted in the fallopian tube; unilateral pelvic pain then occurs periodically in the first four weeks. Dangerous complications arise with increasing growth: Either the fruit is expelled into the free abdominal cavity or the fallopian tube ruptures with severe pain and severe, e.g. T. life-threatening bleeding.

Gestosis? This is a hormone-related disease that occurs in around ten percent of all pregnancies. It manifests itself in the first trimester of pregnancy with increased vomiting or later as so-called late gestosis with water retention, protein in the urine, high blood pressure and coagulation disorders. If cramps also occur, one speaks of eclampsia.

Rubella Embryopathy? An infection of the unborn child with rubella virus during the first three months of pregnancy can cause severe malformations. If infected in the first month of pregnancy, 60 percent of the embryos die. If the mother had rubella before pregnancy or was vaccinated against rubella, this risk is excluded.