3rd week of pregnancy

  • 1st to 7th day of embryonic development

Within 12 hours of ovulation, one of the approximately 200 millions sperm cells has reached and fertilized the egg cell in the fallopian tube. Thereafter, the outer layer of the egg cell hardens so that no additional sperm cells can penetrate.


The fertilized egg cell is only a fraction of a millimetre in size. During the third week, it slowly wanders through the fallopian tube towards the womb. On the way, it continuously divides, growing quickly. After three to four days, when it has reached the uterus, the single cell has transformed into a small cell formation, the morula (mulberry). At the end of the week, a cavity filled with liquid has developed.


At the latest, seven days after fertilization (the end of the third week of pregnancy) the blastocyst lodges itself in the mucous membrane of the uterus (which is prepared for this) and lets itself be covered by it. During this process, slight bleeding can occur, which is often mistaken for the beginning of menstruation. The outer cell layer, the trophoblast, establishes a connection with the mother’s blood vessels during nidation.


Your body reacts to this signal with the production of different hormones, which can cause typical subjective pregnancy symptoms. The most important are: nausea, a sudden sensitivity to smells, frequent urge to pass water (including during the night!), a feeling of tension in the breasts and inexplicable fatigue.


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