Pregnant: What happens in weeks 1-5

How are the pregnancy weeks calculated?

Doctors calculate the course of a pregnancy from the first day of a full cycle, that is, on the first day after the woman's period. From that point the pregnancy lasts about 40 weeks. This method of counting makes mathematical sense, but it also means that you are de facto not yet pregnant in the first two weeks of pregnancy are. Because ovulation usually occurs only at the end of the second week of a cycle. Only then can the egg be fertilized and implant in the uterus. With the absence of the first period, the woman is therefore already in the 4th week of pregnancy.

1. bis 5. Schwangerschaftswoche | Image 2

Pregnancy weeks 1–5 at a glance

Week 1 – the period

Although there may be a fertilized egg in the 1st week of pregnancy, the woman's body is still preparing for a possible pregnancy. For a fertilized egg to implant in the uterus at all, the uterine lining must be thick and well perfused enough. In week 1 the uterus prepares through the period by shedding the old lining and building a new one.

Week 2 – the fertile phase

Even in the 2nd week of pregnancy you are, purely mathematically, still not pregnant. However, the woman's body approaches the middle of the menstrual cycle – the fertile phase begins.

Week 3 – finally pregnant

The actual pregnancy begins at the end of the – purely calculational – 2nd week of pregnancy and the start of week 3, when the egg is fertilized on its way from the fallopian tube to the uterus is. Less than two days after fertilization, the cells in the egg begin to divide: the embryo grows. Even now it is determined whether the baby is female or male.

Note: It is hard to say exactly when ovulation occurred. It may happen that the calculated due date is later adjusted by the doctor if the baby appears more or less mature based on its size and development than it should be according to the calculated current week of pregnancy.

Week 4 – the crucial phase

At the beginning of the 4th week of pregnancy the fertilized egg implants in the uterus. Only if this succeeds does the pregnancy continue. In many cases the egg is expelled so the woman gets her period without noticing the failed pregnancy. If the egg manages to implant, a gestational sac, yolk sac and placenta form around the embryo to supply nutrients to the baby in the first weeks.

Week 5 – pregnancy tests turn positive

In the 5th week of pregnancy the chance increases that already over-the-counter pregnancy tests from the pharmacy or drugstore detect that you are expecting a baby. This is due to the pregnancy hormone hCG, which the mother's body now produces. The embryo has settled into the uterine lining and is busily working to grow. The organ development begins and slowly the heart, blood vessels, connective tissue, lungs and intestines as well as the nervous system and the sex organs develop from the neural groove (the midline of the germ disc) and the germ layers. The umbilical cord between mother and child is now also present. It serves to supply the baby. In addition, the expectant mother's body increasingly produces progesterone is produced. The hormone slows down the metabolism, allowing the embryo to be optimally supplied with nutrients. In general, physical changes increasingly occur from now on.

The size of the embryo in week 5

The embryo is busy trying to reach the one-millimeter mark already in the 4th week of pregnancy. However, it is usually at the beginning of week 5 about 0.5 mm in size. On the ultrasound image it is therefore still quite difficult to see. What can be seen increasingly clearly on the ultrasound, however, is the gestational sac. It appears as a dark shadow on the image and only hints at where your little miracle is safely hidden. Within week 5, the embryo usually grows up to about 2 mm . That corresponds to an orange seed and usually appears elongated, similar to a tadpole.

Physical changes – signs of pregnancy in the mother

First physical symptoms: Many women already feel weak and tired in this early stage of pregnancy, and some also suffer from constipation and the typical nausea. Hormonal changes often cause strong mood swings that are typical for the first trimester of pregnancy.

Period pain or pregnant? Before the end of the 4th week of pregnancy you usually notice nothing of the existing pregnancy. The first physical sign is the absence of the period, but many women also simultaneously feel a pulling in the uterus or experience breast pain or tender breasts. Seven to twelve days after fertilization, that is still in the 3rd or 4th week after the last period, there may be so-called implantation bleeding. This occurs when the fertilized egg implants in the uterine lining and in the process damages blood vessels. The bleeding can be mistaken for a menstrual bleeding, but usually it is only a few drops and lasts only one to two days. A slight pulling in the lower abdomen is completely normal.

The first month of pregnancy: what is important now

Maternity record: As soon as the doctor confirms your pregnancy, he or she will issue your maternity record. It will collect all data and information about the pregnancy up to the birth. Subsequent pregnancies are usually also documented in this maternity record.
Appointment for the first ultrasound examination: The doctor will probably give you an appointment for the first ultrasound between the 9th and 12th week of pregnancy when confirming the pregnancy. In total, three of these examinations are planned – and each is an event for you as expectant parents.
Nutrition during pregnancy: Pay particular attention to not consuming raw (animal) foods. These often contain toxoplasma and listeria, i.e. infectious agents. Therefore, heat your food to at least 70 degrees. Wash fruit, vegetables and salad leaves more thoroughly than you did before and avoid raw milk (products) as well as smoked foods.
Supplements: Most women take iron and folic acid supplements during pregnancy. These nutrients are essential for the health of mother and baby. It's best to have a supplement prescribed by your doctor, as over-the-counter supplements from the drugstore are often underdosed or not suitably combined. Approximately 0.4 milligrams per day are usually enough to support the growth process.
Hygiene: If you own cats, it is advisable that the expectant father takes care of cleaning the litter box. Infectious agents that could harm the baby can also lurk there.

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