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1st to 12th week of pregnancy: What happens in the first trimester of pregnancy?

1st to 12th week of pregnancy: What happens in the first trimester of pregnancy?

In this article you will learn

The first trimester of pregnancy

You may not have a visible baby bump in the first trimester, but a lot happens in the first few weeks of your pregnancy. In this article we answer the most frequently asked questions about the 1st to the 12th week of pregnancy: What are the first signs of pregnancy? How does the embryo develop? Are your nausea and tiredness normal? And why are the first twelve weeks of pregnancy considered dangerous?

But the basics first: A pregnancy is always divided into three pregnancy trimesters, also known as pregnancy trimesters or trimesters. It logically begins with fertilization.

However, the gestational age is calculated from the beginning of the cycle, i.e. from the first day of the last period. This way it is easier to calculate the approximate due date. The pregnancy therefore does not last nine months, but almost ten months.

The pregnancy trimesters at a glance:

In order to keep track of the time during pregnancy and to know the developmental status of the baby, we speak of pregnancy weeks (1st to 40th week of pregnancy) or pregnancy trimesters (first to third pregnancy trimester):

  • First trimester: Weeks 1-12
  • Second trimester: Weeks 13-28
  • Third trimester: Weeks 29-40 SSW

“How do I know I'm pregnant?”

The first sign of pregnancy is often a missed period. If you know your body very well, you may also feel a slight tugging in your abdomen: the egg nests in the uterus. A pregnancy test will give you the first certainty.

You should then have your gynecologist confirm the pregnancy with an examination. A blood test and a vaginal ultrasound are done. If the examination verifies the pregnancy, you will be issued with a maternity pass.

In early pregnancy, i.e. in the first trimester of pregnancy, you may notice that your breasts become tender and larger. It's not uncommon for them to feel heavier and fuller in the first 12 weeks of pregnancy. Many women find their nipples particularly sensitive during this period of their pregnancy because the body produces a particularly large amount of pregnancy hormones at this time.

The hormonal changes in your body can also cause hair and nails to grow faster than usual. Bleeding gums are also not uncommon in this phase of pregnancy due to increased blood formation.

The pregnancy hormones also cause the well-known morning sickness and the feeling of exhaustion or tiredness.

Many pregnant women then ask themselves when this discomfort will stop. As a rule, pregnancy sickness reaches its peak in the 9th week of pregnancy. So most women can breathe easy after the first trimester.

1st to 12th week of pregnancy: What happens in the first trimester of pregnancy?

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“What happens in the first weeks of pregnancy?” 

Yes, what was it like with the bees and flowers? Fertilization takes place when a sperm has fought its way through to the nucleus of the egg cell. The fertilized egg cell divides several times and in a short time a so-called cell cluster is formed. In the next few days, this migrates through the fallopian tube, nests in the 4th week of pregnancy in the uterus and grows there into an embryo.

After the first weeks of pregnancy, the embryo is only a few millimeters in size, but significant developments are already taking place in this trimester: the heart begins to beat in the 5th week of pregnancy, and from the 6th week of pregnancy the heartbeat can even be detected on the ultrasound. At the same time, the embryo develops the first beginnings of the arms and legs. The development of the first organs also begins in the 6th to 8th week of pregnancy. This includes the sensory organs such as the mouth, nose and eyes.

As the first trimester of pregnancy progresses, details such as the upper lip, fingers and toes become even more apparent. In the 9th week of pregnancy, the embryo is already 1.5 to 2 cm in size. At this point, nerve cells and muscles are already sufficiently developed that the embryo can move freely in the amniotic sac. As a rule, however, you cannot feel these movements as a pregnant woman.

Did you know? At 12 weeks the baby is the size of a passion fruit.

Once the first trimester of pregnancy is over, we no longer speak of the embryo but of the fetus. At 12 weeks the baby is the size of a passion fruit.

“What needs to be considered in the first few weeks of pregnancy?”

It is true that the risk of miscarriage is particularly high in the first twelve weeks of pregnancy. This is because the fertilized egg cell has to implant properly first. Failure to do so can result in an ectopic pregnancy or miscarriage. Your consulting gynecologist will inform you and discuss individually what personal risks exist in your pregnancy. These include your age, your health and that of the child's father.

But don't worry, there are many ways you can support yourself, your body and the development of your child in the first few weeks of pregnancy . First and foremost, it is important to reduce your own stress level, to take a breather and to guarantee the supply of vitamins, minerals and other nutrients through a healthy diet.

“What do I need folic acid for during pregnancy?”

In addition to a balanced diet, it is also recommended to take folic acid before and during pregnancy. Folic acid is a B vitamin that is converted by the body into the active form of folic acid, folate. The human body needs folate for cell division, i.e. in the first few days after fertilization. In addition, folate plays an important role throughout pregnancy, as it supports blood formation and the growth of the placenta.

Especially in the first trimester of pregnancy, it is advisable to take folic acid as a dietary supplement. Otherwise, you would have to eat almost 3 kg of oranges every day to get enough from food alone. It is best to get advice from your gynecology practice so that you can enjoy the first twelve weeks of pregnancy with good care.

If you want to know what happens in the second trimester of pregnancy, click here!