The first trimester

Synonyms

1st trimester of pregnancy, 1st trimester

definition

Under the term “1. Trimester is the first part of pregnancy. The 1st trimester begins with the first day of the last menstrual period and ends with the beginning of the 13th week of pregnancy (pregnancy week 12 + 6).

Course of the 1st trimester

The 1st trimester begins before the actual pregnancy occurs on the first day of the last menstrual period and lasts until the 12th week of pregnancy. Based on the first day of the last menstrual period, an expected due date can be calculated within the first weeks of pregnancy. However, this preliminary due date is for guidance only.
Due to the fact that many women have a rather irregular menstrual cycle in which ovulation does not take place between the 12th and 14th day of the cycle, the fertilization of the egg can also take place late. In addition, based on the calculation of the approximate week of pregnancy, important conclusions can be drawn about whether the unborn child is developing on time.
Most women notice during the 1st trimester that fertilization has taken place. In particular, the typical pregnancy symptoms, such as pronounced tiredness and frequent vomiting, can indicate pregnancy at an early stage. However, because the first symptoms of pregnancy often resemble normal premenstrual symptoms, not every woman immediately realizes that a pregnancy exists. Only in the middle of the 1st trimester can the absence of a menstrual period and a positive pregnancy test confirm the first suspicion.

Development of the child in the 1st trimester

The first trimester begins before the actual pregnancy occurs on the first day of the last menstrual period. Within the first week of this trimester, the egg cell matures as well as ovulation (approximately between the 12th and 14th day of the cycle).
After ovulation, the mature egg remains fertile for a period of about 12 hours. When the egg cell and sperm fuse together, what is known as the “seedling”, which will later become the embryo, is formed. Immediately after successful fertilization, the egg cell begins to divide several times. By the end of the third week of the 1st trimester, the fertilized egg has divided several times and prepared for implantation. In addition to the child's dispositions, parts of the later placenta also form from the fertilized egg cell.

From the eighth day of development, the cells of the so-called "embryoblast" are arranged in three layers on top of one another (Cotyledons) on. At this point the outer (Ectoderm) and the inner cotyledon (Endoderm). In addition, a small space, the so-called amniotic cavity, forms over the outer cotyledon. This amniotic cavity continues to expand in the further course of the 1st trimester of pregnancy and forms the inner part of the amniotic sac.

While the cells of the outer cotyledon form the nervous system (Brain, spinal cord, peripheral and central nervous system), which form the sweat glands, tooth enamel and nails, most internal organs arise from the inner cotyledon. Bones, muscles and blood vessels are made up of a layer of cells between the ectoderm and endoderm. The child's heart begins to develop within the first 4 weeks of the 1st trimester of pregnancy. About the sixth week of pregnancy, the heart activity of the unborn child can be detected using ultrasound.

The most important systems of the organism are already fully formed in the tenth week of the 1st trimester of pregnancy. In addition, all of the child's organs are created in the first trimester of pregnancy. The ears, eyes and eyelids are also developed by the end of the 12th week of pregnancy. On average, by the end of the 1st trimester, the fetus reaches a length of nine centimeters (from crown to rump) and a weight of around 40 to 50 grams.

Read more on the topic: Development of the embryo

Changes and complaints in the 1st trisemester

The first trimester of pregnancy is perceived as particularly uncomfortable by many of the expectant mothers. The main reason for this is the body's hormonal changes.
The rise in the pregnancy hormone beta-hCG causes various symptoms to develop in most women. The mother-to-be's body has to adapt to the needs of the embryo in the first trimester of pregnancy. In addition, various hormones that prepare the abdomen (especially the uterus) for the growth of the unborn child are released. The expectant mother's entire hormonal balance must therefore regulate itself in the first trimester of pregnancy. In addition, the metabolism is also subject to enormous changes, which can be accompanied by pronounced symptoms.

The typical symptoms in the first trimester of pregnancy include the notorious pregnancy sickness, frequent vomiting, pronounced fatigue and circulatory problems. In many women, blood pressure can drop so much during the first trimester of pregnancy that they may feel dizzy and faint. For this reason, expectant mothers should ensure that they drink enough fluids, especially in the first trimester of pregnancy.

Other typical complaints in the 1st trimester of pregnancy are headache and mild back pain. In addition, a significant acceleration in the growth of nails and hair can be observed in the expectant mothers in early pregnancy. Due to the increased blood flow, bleeding gums are also one of the most common complaints in the 1st trimester of pregnancy.

The mother-to-be's body prepares at the beginning of pregnancy to cope with the rapid growth of the child. For this reason, various hormones that induce loosening of the ligaments and muscles are increasingly synthesized and released. As a side effect of these pregnancy hormones, there may be other typical symptoms. Many women feel the loosening of the ligaments in the form of pulling or stabbing pain in their right and / or left abdomen. Since the uterus often tilts slightly to the right side during pregnancy, the symptoms are often more pronounced in the right abdomen.

In addition, hormone-related hair loss is one of the most common complaints that occur in the 1st trimester of pregnancy. However, with a balanced diet and careful hair care, hair loss typically subsides after a few weeks.

Although many women assume that an increased urge to urinate is one of the symptoms of late pregnancy, the pressure of the growing uterus can already lead to impaired bladder function in the 1st trimester. Since the mother-to-be's genital organs are already supplied with much more blood in the first trimester of pregnancy, there is usually increased secretion and vaginal discharge.

Furthermore, most of the expectant mothers suffer from severe mood swings in the 1st trimester of pregnancy. During this third of their pregnancy, some women permanently switch between euphoric and depressive phases. However, these symptoms can be traced back to the rapid increase in pregnancy hormones and usually recede completely within the second trimester of pregnancy. Fortunately, the nausea typical of pregnancy only lasts until the end of the first trimester in most women.

Read more about this: Pregnancy complications

Screening exams in the first trimester

There are various examinations in the first three semester, which are mainly used to detect malformations in growing children. The prenatal test, a special blood test and the neck transparency measurement are particularly well known.

Blood test

Screening in the 1st trimester of pregnancy is primarily used to monitor child development. In addition, if desired, various examinations for the detection of hereditary diseases (especially so-called chromosomal abnormalities), for example Down's syndrome, can be carried out with a prenatal test. Screening in the 1st trimester of pregnancy can be done between the 12th and 14th week of pregnancy. As a rule, screening in the 1st trimester of pregnancy can check various blood values ​​for a possible chromosomal abnormality.
Above all, the pregnancy-specific protein, the pregnancy-associated plasma protein A (PAPP-A for short) and the free beta subunit of HCG play a decisive role. While the PAPP-A is typically significantly reduced in the presence of Down's syndrome, there is a significant increase in the free beta-HCG in mothers of affected children.

Read more on the subject at: Prenatal test

Neck fold measurement

In addition to the specific Blood tests When screening in the 1st trimester of pregnancy, the so-called Neck fold measurement (Neck transparency measurement) be performed. The term "neck transparency" means a slightly darker area that corresponds to liquid in the child's neck area. In general, it can be assumed that the neck fold is something perfectly normal and can be detected in most children in the 1st trimester of pregnancy.
However, a particularly high degree of nuchal transparency is associated with an increased risk of having a chromosomal abnormality, for example Down's syndrome (trisomy 21). Nevertheless, it should be noted in this examination in the screening of the 1st trimester of pregnancy that most children with enlarged neck folds still have no chromosome changes.
For this reason, the measurement of the nuchal folds as screening in the 1st trimester of pregnancy is considered quite controversial. It can only be a first indication of a child's developmental disorder and is more likely to have an effect on expectant mothers unsettling as helpful.

Summary

Human pregnancy is medically in three roughly equal sections structured. The division of pregnancy into a first, a second and a third trimester mainly serves to separate different stages of development of the unborn child.

The 1st trimester Pregnancy begins even before the egg is actually fertilized, on the first day of the last menstrual period. On the basis of this reference date, the possible due date can be calculated approximately at the beginning of the pregnancy. The expectant mother can develop it especially in the 1st trimester of pregnancy severe discomfort come. The main reason for this is the rapid rise in the pregnancy hormone beta-hCG. Typical symptoms of this stage of pregnancy include extreme tiredness, nausea, frequent vomiting, headaches and mood swings. Contrary to popular belief, early pregnancy does not only lead to severe nausea and vomiting in the morning hours. Affected women usually suffer from more or less pronounced symptoms throughout the day. Fortunately, most of the typical symptoms of the first part of pregnancy disappear completely by the end of the first trimester.

Child development in the 1st trimester of pregnancy involves a multitude of steps. During the first weeks before the actual start of pregnancy the egg begins to mature. Approximately between the 12th and 14th day of the menstrual cycle occurs ovulation. From this point on, the egg can be fertilized over a period of approximately 12 hours. After successful fertilization, the first cycles of division begin in the fallopian tube. A few days later, she can implant the fertilized egg cell in the uterus.

Within the 1st trimester of pregnancy will be nearly all of the child's organ systems created. For this reason, it is especially important that the expectant mother balanced and healthy food. Mainly on the adequate intake of Folic acid and Vitamins should be strictly observed in the 1st trimester of pregnancy. The 1st trimester of pregnancy ends with the beginning of the 13th week of pregnancy. At this point the risk of one decreases Miscarriage to a value of about 1-2 percent.