|
Fetal position reflects
the orientation of the fetal head or butt within the birth
canal.
Anterior FontanelAnterior
Fontanel
The bones of the fetal scalp are soft and meet at "suture
lines."
Over the forehead, where the bones meet,
is a gap, called the "anterior fontanel," or "soft spot." This
will close as the baby grows during the 1st year of life, but at
birth, it is open.
The anterior fontanel is an obstetrical
landmark because of its' distinctive diamond shape.
Feeling this
fontanel on pelvic exam tells you that the forehead is just
beneath your fingers.
Early in labor, it is usually difficult
(if not impossible) to feel the anterior fontanel. After the mom
is nearly completely open, it becomes easier to feel the
fontanel.
Posterior FontanelPosterior
Fontanel
The occiput of the baby has a similar obstetric landmark, the
"posterior fontanel."
This junction of suture lines in a
Y shape that is very different from the anterior fontanel.
In cases of fetal scalp swelling or
significant molding, these landmarks may become obscured, but in
most cases, they can identify the fetal head position as it is
engaged in the birth canal
Occiput
Anterior (OA)Occiput
Anterior
(OA)
Occiput anterior is usually the
easiest position for the fetal head to traverse the maternal
pelvis.
Shown here is the "direct OA" position. While
some fetuses deliver in this position, others deliver slightly
rotated clockwise (LOA) or counterclockwise (ROA). Either way,
the fetus is still considered to be an an "anterior" position
Left
Occiput Anterior (LOA)
Left Occiput Anterior
(LOA)
Right Occipuat Anterior (ROA)The
fetal position is often described using three letters.
This is an
example of LOA, meaning:
In other words, the fetal occiput is directed
towards the mother's left, anterior side.
 Right
Occiput Anterior (ROA)
This is an example of ROA, meaning:
These anterior presentations (ROA and LOA)
are normal and usually are the easiest way for the fetus to
traverse the birth canal.
Left Occiput Transverse (LOT)Transverse
Position
This
LOT (Left, Occiput, Transverse) position and its' mirror image,
ROT, are common in early labor.
Occiput Posterior (OP)As
labor progresses and the fetal head descends, the occiput
usually rotates anteriorly, converting this LOT to an LOA or OA
as the head delivers.
If the head fails to rotate despite steady descent, this is
called a "deep transverse arrest," and is common among:
- Babies who are too big to come through,
and
- Mothers with flat pelvises that favor a
transverse delivery
 Sometimes
Women with this condition who
fail to deliver spontaneously are treated with cesarean section,
forceps, or vacuum extraction, depending on the clinical
circumstances, available resources, and experience of the
operator.
Right Occiput Transverse (ROT)Occiput
Posterior
Occiput posterior positions, including direct OP, LOP (Left
Left Occiput Posterior (LOP)Occiput
Posterior) and ROP (Right Occiput Posterior) are positions
favored by certain internal pelvic shapes. This position has
some obstetrical significance.
- Normally, if the head is at 0 Station,
the biparietal diameter is at the pelvic inlet and the head
is fully engaged. In posterior positions, at 0 Station, the
biparietal diameter is still a couple centimeters above the
pelvic inlet, meaning that the head is not fully engaged.
- Babies can deliver
in the posterior position, but the pelvis needs to be large
enough and it usually takes longer.
- Forceps are often used to deliver babies
in this position, but there is controversy whether the fetus
should be delivered in the posterior position, or rotated
with the forceps to the anterior position. Much depends on
the clinical circumstances and the experience of the
operator.
Right Occiput Posterior (ROP)Breech
Positions
The terms used for breech
positions are the same as for cephalic positions, except the
sacrum of the fetus is used as the identifying landmark, instead
of the occiput.
Right Sacrum Posterior (RSP)
- Sacrum Anterior
(SA) means the fetal sacrum is closest to the mother's
symphysis.
- Left Sacrum Anterior (LSA) means the
fetal sacrum is closest to the mother's symphysis and
rotated slightly to the mother's left (clockwise from direct
SA).
- Right Sacrum Anterior (RSA) means the
fetal sacrum is closest to the mother's symphysis and
rotated slightly to the mother's right (counterclockwise
from direct SA).
- Right Sacrum
Transverse (RST)
- Left Sacrum Transverse (LST)
- Right Sacrum Posterior (RSP)
- Left Sacrum Posterior (LSP)
- Sacrum Posterior (SP)
OB-GYN 101: Introductory Obstetrics & Gynecology
© 2003, 2004, 2006
Medical Education Division, Brookside Associates, Ltd.:
All rights reserved
http://www.brooksidepress.org/Products/OBGYN_101/MyDocuments4/Text/malLD/fetal_position.htm
|
Pat
is a HypnoBirthing® Practitioner, Certified in the
Mongan Method by the
