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6.4 Implantation anomalies
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Extra-uterine gravidity (EUG)
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An extra-uterine pregnancy (EUG = extra-uterine gravidity) is a rare, but serious complication (2,5% of all pregnancies). It can lead to hemorrhages and thus to sterility (due to rupture of the fallopian tube).
Normal fertilization always takes place outside the uterus, in the outer third of the tube. The fertilized oocyte migrates through the tube to the uterus. The implantation takes place on the 6th day in the uterine endometrium. If this migration is delayed for whatever reason, the blastocyst can implant itself somewhere along the way to the uterus. Most often this happens in the tube (99% of the EUG are tubal pregnancies).
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| Fig. 28 - Possible ectopic implantation zones |
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In the ovary
In the infundibulum
In the fallopian tube
In the isthmus
Deep in the uterus (location for a later placenta previa)
Abdominal (on an intestinal loop)
In the pelvis |
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Fig. 28
Tubal pregnancies occur the most often (99%).
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Extra-uterine gravidities (EUG) can occur in healthy uterine tubes; this happens roughly 10% of the time and is possibly connected with:
- A delayed capture of the oocyte by the infundibulum
- A disturbance of the peristalsis in the tube (traced back to the effects of ovulation inductors and certain medications)
Most frequently, extra-uterine pregnancies appear in pathologic tubes (approximately 90%). Organic hindrances, often bilateral, are responsible. They frequently lead to relapses and later to sterility.
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There are a total of 6 potential risk factors which can lead to EUGs:
- Infections (fallopian tube infection, salpingitis)
- Surgical interventions in the pelvis
- Tobacco misuse
- In vitro fertilization (IVF)
- Congenital anomalies (tube malformations)
- Endometriosis (ectopic fragments of the uterine mucosa)
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Video
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IVF: Insemination via intracytoplasmic sperm cell injection (ICSI). (3 MB)
© Prof. B. Imthurn, Unispital, Zürich
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When the implantation takes place in the lower part of the uterus, the placenta will later develop in the cervix uteri. This type of implantation is called placenta previa. A birth through the birth canal would detach the placenta before the fetus is born. This can lead to serious hemorrhages. For this reason, a caesarian section is always used for enabling births in such situations. Placenta previas occur in 1% of all pregnancies.
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