Birth Presentations and Delivery
Presentation is the term doctors use to denote the position of the baby as it exits the birth canal. The orientation of the baby can make a big difference in how difficult the birthing process is.
Almost all babies (approximately 95%) present themselves in what is known as the "normal presentation." The other 5% of babies are oriented at birth in such a way that they are known as "fetal malpresentations." So what makes a "normal presentation" normal? There are three factors, whether or not each is "normal" dictates how difficult the birth will be and whether a repositioning, c-section or episiotomy is necessary.
The Fetal Lie
This term refers to the position of the baby’s spine relative to the mother’s. For a "normal" fetal lie, the baby’s spine must be in the same direction as the mother’s. This is also called a "cephalic" lie. If it is at an angle to the mother’s spine, it is said to have an "oblique lie." If it is completely transverse to the mother’s spine (90 degree angle), it is said to have a "transverse lie."
The main danger that a transverse or oblique lie presents is the fact that there is nothing blocking the birth canal when the mother’s water breaks. If it does, there is a danger that the umbilical cord can exit the birth canal, depriving the baby of blood and oxygen, potentially causing organ, tissue, or brain damage. This occurrence is known as cord prolapse. It is especially likely with a transverse lie.
A transverse or oblique lie occurs in approximately 1 in 300 births. Odds are increased if the birth is premature.
This factor of Presentation is given the same name as the overall term. It refers to what part of the baby is set to appear first from the birth canal. For normal presentation, the crown of the head should be first. Anything other than this constitutes a malpresentation. The malpresentations fall into a number of categories.
A breech presentation refers to when the baby emerges feet, buttocks, or knees first. Often babies exist in the breach position for much of pregnancy but then manage to orient themselves to the normal position shortly before birth. There are five different kinds of breech births possible.
Frank Breech: The baby’s legs are bent upwards, putting it in a "V" position. The buttocks and pelvis are in the birth canal.
Complete Breech: The baby is sitting cross-legged, pelvis and buttocks in birth canal.
Incomplete Breech: The same as complete breech but with one leg dangling and leading the way out of the birth canal.
Footling: Like Frank breach, only one leg is raised, the other is dangling and leading the way out of the birth canal.
Double Footling: Both feet exiting the birth canal first.
A breech presentation will often mean a longer labor time, as the buttocks do not open the birth canal as efficiently as the head. Forceps or a vacuum extractor may be used to assist in this case.
Another possibility is for the doctor, with the help of ultrasound, to attempt to rotate the baby into head down position by applying gentle pressure to the mother’s abdomen. This must be done before the 37th week otherwise amniotic fluid makes it too difficult to rotate the baby. There is also a risk of tearing the placenta from the uterine wall when doing this.
This occurs when two different parts of the baby are set to exit the birth canal at the same time. For example: an arm alongside the head. Unless the pelvis is large enough to handle the extra width, an episiotomy or c-section must be performed.
This happens when the shoulders are presented first, with the head tucked inside. If this occurs, the baby must either be repositioned or delivered via c-section. Odds of a shoulder presentation are one in 1,000.
This factor refers to the position of the baby’s head. For a normal presentation, the head should be tucked down, into the chest. The two malpresentations for this factor are:
Face Presentation: The baby is looking up, set to emerge face first.
Brow Presentation: The baby’s head is in between the normal presentation and the face presentation. The forehead emerges first.
The odds of an irregular flexion attitude are approximately one in 500. If it occurs, a c-section may be necessary.
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