Until the end of 8 gestation week called the growing fetusembryo.
After fertilization of the egg head wanders the fertilized eggs, while the shares themselves, to the uterus. At around. 4th days after fertilization, it has been for a clump of cells calledblastocyst. The cells in the blastocyst develops later in the embryo and the placenta. Around the 7th days after fertilization grow it on livmoderslimhinden (calledimplantationornidationen).
Precursor to the placenta is formed by indvækst of blastocyst cells in 
livmoderslimhinden, and cell proliferation in the embryonic cells continues. It formed a plate of cells, which later grows and unfolds, so the embryo is formed. It has size and appearance, as seen in the illustration. The heart and vasculature formation begins in 3rd week, and one can detect fetal heart rate by an ultrasound examination 5 weeks after fertilization. Arms and legs are developed primarily as ekstrimetetsknopper, and the nervous system is formed by a convolution of the aforementioned sheet to a tube (neuralrøret), which becomes the brain and spinal cord.
Through the umbilical cord is the transport of nutrients, oxygen and waste in the blood between the embryo / fetus and placenta. Over parent pie is large surface exchange with the mother. Thus transported food and oxygen to the embryo / fetal blood, and waste is then transported to the mother's blood.
| 
