5th week of pregnancy

  • 15th to the 21st day of embryonic development
  • length of embryo: 2 mm

It’s been more than four weeks since your last menstruation; the next one is overdue. Perhaps you already suspect that you are pregnant. At the end of this week, a pregnancy test will probably be able to confirm your suspicion.


In the 5th week of pregnancy the embryo’s head and trunk can be recognized. Its appearance changes through the increased growth of the head and anlagen of the face and extremities. The anlagen of the arms and legs appear as paddle-like buds. The nervous system develops rapidly now: the neural groove closes, and thus the neural tube is formed from which the brain and spinal cord later develop.


Any disturbance or damage during this important phase can lead to a deformation in this area (neural tube defect). The risk of a neural tube defect can be significantly lowered by folic acid and multivitamin supplements for pregnancy. This is why one should start taking supplements as early in the pregnancy as possible – preferably several months before, if you plan your pregnancy.


The development of the larger inner organs, the bones, muscles, blood vessels and the blood starts now. At the end of the 5th week, the still tube-like embryonic heart is already beating steadily, pumping liquid into the few tiny blood vessels. With high-resolution ultrasound scanners the heart activity can be seen.


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