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The placenta previa is characterized by a low-lying insertion location in the uterus (close to the cervix). The natural birth canal can be partially or completely plugged up thereby and represent a mechanical obstacle during delivery through the vagina. This pathology affects 0,5% of all pregnant women. The placenta previa is life-threatening to the fetus and also for the mother. The latter risks hemorrhages due to a detachment of the placenta that occurs too early during uterine contractions or cervix dilatation. The precise causes for a placenta previa are as yet unknown, but multiparity and preceding miscarriages create favorable conditions for it to happen. In addition, it has been established that scarring and uterine abnormalities, fibroma and twin pregnancies also represent risk factors.
Ectopic, i.e., extra-uterine pregnancies occur in approximately one woman in 300. They arise through an implantation of the embryo at another location than in the uterine cavity. The most frequent location is that of the fallopian tube (roughly 85%). Implantations in the ovary, in the abdominal cavity or in the intra-uterine pars of the fallopian tube can ensue. Possible explanations for these ectopic implantations could be a delayed taking up of the oocyte or the slowed emigration through the fallopian tube. Anatomic reasons also exist such as fallopian tube abnormalities and stenosis that can arise following infections of the fallopian tube. Functional factors can also be mentioned (surgical reconstruction of the fallopian tube, intrauterine devices).
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