The first trimester is the period from the 1st to the 13th week of pregnancy. This time is very stressful for many pregnant people. Your body changes under the influence of various hormones. Many pregnant people experience discomforts and emotions can be roller coaster ride. All the baby's major organs are formed at this stage. The heart starts to beat and the brain and nervous system form. You will see the developing baby for the first time between the 9th and 12th week of pregnancy at your first ultrasound examination. You should know that the first few weeks after fertilisation are critical. 80 percent of all miscarriages occur during this sensitive period. The further the pregnancy progresses, the lower the risk becomes. By the 15th week of pregnancy, the risk of miscarriage is only one to three percent.

Your body begins to change from the first day of pregnancy. This is due to the hormones that are now increasingly released. Progesterone and hCG loosen the lining of the uterus and the connective tissue so that the embryo can implant and then grow unhindered. Oestrogen cause the breasts to grow in early pregnancy, preparing the body for breastfeeding after birth. Hormonal changes may be associated with pregnancy discomfort. The most common kinds of discomfort include nausea and vomiting, tenderness in the breasts, fatigue or insomnia. Some people are especially sensitive to smells or tastes during this time. Some find that they need to go to the bathroom more often than usual. The hormone progesterone is also responsible for the increased urge to urinate. It relaxes the muscles around the bladder, which then reacts sensitively to even slight pressure. Your heart is beating harder too. That's because it's now pumping more blood through your body. Your blood vessels are dilating, which can have several side effects. Spider veins or varicose veins are common, as are nosebleeds, a stuffy nose or bleeding gums. Many people find the first trimester of pregnancy to be stressful. They usually do much better in the second trimester.

After ovulation, the egg moves towards the uterus. At the moment of fertilisation, it is still in the fallopian tube. The developing cell, the zygote, then migrates onwards and nests in the loosened uterine lining. After the fourth week of pregnancy the embryo measures one to two millimetres, in the sixth week of pregnancy it has already grown to four millimetres. The outline of the torso and head are clearly visible at this point, as are the arms and legs. The development of the lungs, neural tube and nerve cells begins.

Sometimes several eggs are fertilised at the same time. If this happens, there will be twins on the way, maybe even triplets or quadruplets. In other cases, the fertilised egg cell divides immediately after fertilisation. This is what leads to identical twins or multiples. A multiple pregnancy is confirmed at the ultrasound examination during the 9th week of pregnancy at the earliest.

The embryo grows from the top down. You can tell by the relatively large head. Facial features slowly develop. The mouth and tip of the nose can be detected and eyelids appear above the still open eyes. The brain is already sending signals and responding to impulses. But developments aren’t just happening around the head; the spinal column also continues to form and the internal organs develop as well. The embryo is about 15 millimetres long at the end of the second month of pregnancy. During the ultrasound measurement, your doctor will determine the distance between the crown of the embryo’s head and its tailbone. They can tell if it is developing in a timely manner. The term ‘crown-rump length’ (Scheitel-Steiß-Länge) is abbreviated to SSL in Germany. This abbreviation is also used in your maternity record (Mutterpass), where the measurement is entered.

You will see the developing baby for the first time between the 9th and 12th week of pregnancy at your first ultrasound examination. The heartbeat should be visible by the time you have this ultrasound. All of the internal organs are in place in the 9th week of pregnancy. From now on we no longer speak of an embryo but of a fetus. Skull bones, which will remain soft and cartilaginous for a long time, surround the brain, which has been quite unprotected. The face continues to develop, ears can be seen and the buds of teeth are forming. The trunk, limbs and sex organs also change. You can see toes and fingers on the arms and legs . By the end of the third month of pregnancy, the fetus is very active. But its movements are not yet noticeable to you. The fetus measures about six centimeters at the end of the first trimester.

In the first third of pregnancy, there are usually two preliminary check-ups, the results of which are recorded in your maternity record (Mutterpass). Pregnancy is confirmed during the first check-up. You can expect to have your first ultrasound around the 9th week of pregnancy.