Introduction
In the uterus, the child can adopt different positions in relation to the maternal pelvis and the uterus. First, the child lies head up in the uterus. At the end of the pregnancy, the child normally turns so that the child’s head is lying at the exit of the pelvis and the breech is pointing upwards.
This birth position, in which most children are born, is also called the skull position. The head can thus be born first during the birth process. A natural birth has the least complications in the cranial position. However, at the end of the pregnancy, the child can also take up other positions. These are then referred to as positional anomalies.
Definition of the breech end position
The breech presentation is a positional anomaly because it deviates from the normal birth position of the child. The breech presentation occurs in only about 5% of births. In premature babies, the breech presentation is much more common because the child has not yet rotated at the time of birth.
The breech presentation can again be divided into different forms. The breech-only position is the most common. In this case the baby’s bottom, i.e. the rump, is located at the mother’s pelvic outlet.
The feet are turned upwards and the head is located at the upper edge of the uterus, the fundus uteri. The child therefore adopts a kind of sitting position. This form of pelvic end position is the most common and, in the case of natural birth, also harbours the fewest complications. Furthermore, the foot position (the child’s legs are stretched out and thus lie at the exit of the pelvis), the rump-foot position (here the feet precede the rump at birth – “squatting position of the child”) and the knee position are the rarest forms. Furthermore, a distinction is made between a perfect position, in which the legs lie down, i.e. the child assumes a kind of squatting position, and an imperfect position, in which one of the child’s legs points upwards towards the head and rests against the child’s upper body.
Causes of the breech presentation
Up to the 20th week of pregnancy, about half of the children are still in the final pelvic position, but this number is reduced in the further course of the pregnancy by physiological rotation of the child into the birth position. There can be various reasons for remaining in the pelvic floor position until the end of pregnancy, which sometimes interact. Often the exact cause remains unexplained.
Pelvic end positions occur more frequently in premature babies because the child would not rotate until later in the pregnancy. Furthermore, pelvic floor end positions are more common in multiple pregnancies because there is not enough space in the uterus for the rotation of the children, so the children remain in the pelvic floor end position. In addition, low weight, developmental delays or malformations of the child can also play a role.
But also a narrowed or small pelvis of the mother, as well as malformations or fibroids of the uterus, or a very deep-seated placenta (placenta praevia) can contribute to the final pelvic position of the child. Furthermore, an increased amount of amniotic fluid (polyhydramnion) or too little amniotic fluid (oligohydramnion) can also play a role. Due to the increased amount of fluid, the child has more room for movement, but at the same time there is no support to carry out the rotation. If the amount of amniotic fluid is too small, the child lacks the freedom of movement that would be necessary for the rotation.
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