Cephalic presentation
Encyclopedia
A cephalic presentation is a situation at childbirth
where the fetus is in a longitudinal lie
and the head
enters the pelvis first; the most common form of cephalic presentation is the vertex presentation where the occiput
is the leading part (the part that first enters the birth canal). All other presentations are abnormal (malpresentations) which are either more difficult to deliver or not deliverable by natural means.
and the occiput
leads the way. This is the most common configuration and seen at term in 95% of singletons. If the head is extended, the face
becomes the leading part. Face presentations account for less than 1% of presentations at term. In the sinicipital presentation the large fontanelle
is the presenting part; with further labor the head will either flex or extend more so that in the end this presentation leads to a vertex or face presentation. In the brow presentation the head is slightly extended, but less than in the face presentation. The chin presentation is a variant of the face presentation with maximum extension of the head.
Non-cephalic presentations are the breech presentation (3.5%) and the shoulder presentation
(0.5%).
In the vertex presentation the occiput typically is anterior and thus in an optimal position to negotiate the pelvic curve by extending the head. In an occiput posterior position, labor becomes prolonged and more operative interventions are deemed necessary. The prevalence of the persistent occiput posterior is given as 4.7 %
The vertex presentations are further classified according the position of the occiput, it being right, left, or transverse, and anterior or posterior:
The Occipito-Anterior position is ideal for birth - it means that the baby is lined up so as to fit through the pelvis as easily as possible. The baby is head down, facing the spine, with his back on one side of the front of the tummy. In this position, the baby's chin is tucked onto his chest, so that the smallest part of his head will be applied to the cervix first. The position is usually 'Left Occiput Anterior' or LOA - occasionally the baby may be Right Occiput Anterior or ROA.
and other malformations, cephalopelvic disproportion
, and polyhydramnios
. In an uncomplicated face presentation duration of labor is not altered. Perinatal losses with face presentation occur with traumatic version and extraction and midforceps procedures Duff indicates that the prevalence of face presentations is about 1/500–600., while Benedetti et al. found it to be 1/1,250 term deliveries.
Face presentations are classified according to the position of the chin
(mentum):
-shaped) morphology of the uterus
has been given as the major cause for the finding that most singletons favor the cephalic presentation at term. The fundus
is larger and thus a fetus will adapt its position so that the bulkier and more movable podalic pole makes use of it, while the head moves to the opposite site. Factors that influence this positioning include the gestation
al age (earlier in gestation breech presentations are more common as the head is relatively bigger), size of the head, malformations, amount of amniotic fluid
, presence of multiple gestations, presence of tumors, and others.
Two-thirds of all vertex presentations are LOA, possibly because of the asymmetry created by the descending colon
that is on the left side of the pelvis.
delivers the precise diagnosis and may indicate possible causes of a malpresentation. On vaginal examination, the leading part of the fetus becomes identifiable after the amniotic sac
has been broken and the head is descending in the pelvis.
Childbirth
Childbirth is the culmination of a human pregnancy or gestation period with the birth of one or more newborn infants from a woman's uterus...
where the fetus is in a longitudinal lie
Presentation (Obstetrics)
In obstetrics, the presentation of a fetus about to be born refers to which anatomical part of the fetus is leading, that is, is closest to the pelvic inlet of the birth canal. According to the leading part, this is identified as a cephalic, breech, or shoulder presentation...
and the head
Head
In anatomy, the head of an animal is the rostral part that usually comprises the brain, eyes, ears, nose and mouth . Some very simple animals may not have a head, but many bilaterally symmetric forms do....
enters the pelvis first; the most common form of cephalic presentation is the vertex presentation where the occiput
Occiput
The occiput is the anatomical term for the posterior portion of the head, in insects the posterior part of those head capsule.-Clinical significance:Trauma to the occiput can cause a basilar skull fracture....
is the leading part (the part that first enters the birth canal). All other presentations are abnormal (malpresentations) which are either more difficult to deliver or not deliverable by natural means.
Classification
In the vertex presentation the head is flexedFlexion
In anatomy, flexion is a position that is made possible by the joint angle decreasing. The skeletal and muscular systems work together to move the joint into a "flexed" position. For example the elbow is flexed when the hand is brought closer to the shoulder...
and the occiput
Occiput
The occiput is the anatomical term for the posterior portion of the head, in insects the posterior part of those head capsule.-Clinical significance:Trauma to the occiput can cause a basilar skull fracture....
leads the way. This is the most common configuration and seen at term in 95% of singletons. If the head is extended, the face
Face
The face is a central sense organ complex, for those animals that have one, normally on the ventral surface of the head, and can, depending on the definition in the human case, include the hair, forehead, eyebrow, eyelashes, eyes, nose, ears, cheeks, mouth, lips, philtrum, temple, teeth, skin, and...
becomes the leading part. Face presentations account for less than 1% of presentations at term. In the sinicipital presentation the large fontanelle
Fontanelle
A fontanelle is an anatomical feature on an infant's skull.-Anatomy:Fontanelles are soft spots on a baby's head which, during birth, enable the bony plates of the skull to flex, allowing the child's head to pass through the birth canal. The ossification of the bones of the skull causes the...
is the presenting part; with further labor the head will either flex or extend more so that in the end this presentation leads to a vertex or face presentation. In the brow presentation the head is slightly extended, but less than in the face presentation. The chin presentation is a variant of the face presentation with maximum extension of the head.
Non-cephalic presentations are the breech presentation (3.5%) and the shoulder presentation
Shoulder presentation
A shoulder presentation refers to a malpresentation at childbirth where the baby is in a transverse lie , thus the leading part is an arm, shoulder, or the trunk...
(0.5%).
Vertex presentation
The vertex is the area of the vault bounded anteriorly by the anterior fontanelle and the coronal suture, posteriorly by the posterior fontanelle and the lambdoid suture and laterally by 2 lines passing through the parietal eminences.In the vertex presentation the occiput typically is anterior and thus in an optimal position to negotiate the pelvic curve by extending the head. In an occiput posterior position, labor becomes prolonged and more operative interventions are deemed necessary. The prevalence of the persistent occiput posterior is given as 4.7 %
The vertex presentations are further classified according the position of the occiput, it being right, left, or transverse, and anterior or posterior:
- Left Occipito-Anterior (LOA), Left Occipito-Posterior (LOP), Left Occipito-Transverse (LOT);
- Right Occipito-Anterior (ROA), Right Occipito-Posterior (ROP), Right Occipito-Transverse (ROT);
The Occipito-Anterior position is ideal for birth - it means that the baby is lined up so as to fit through the pelvis as easily as possible. The baby is head down, facing the spine, with his back on one side of the front of the tummy. In this position, the baby's chin is tucked onto his chest, so that the smallest part of his head will be applied to the cervix first. The position is usually 'Left Occiput Anterior' or LOA - occasionally the baby may be Right Occiput Anterior or ROA.
Face presentation
Factors that predispose to face presentation are prematurity, macrosomia, anencephalyAnencephaly
Anencephaly is a cephalic disorder that results from a neural tube defect that occurs when the cephalic end of the neural tube fails to close, usually between the 23rd and 26th day of pregnancy, resulting in the absence of a major portion of the brain, skull, and scalp...
and other malformations, cephalopelvic disproportion
Cephalopelvic disproportion
Cephalo-pelvic disproportion exists when the capacity of the pelvis is inadequate to allow the fetus to negotiate the birth canal. This may be due to a small pelvis, a nongynecoid pelvic formation, a large fetus, or a combination of these factors...
, and polyhydramnios
Polyhydramnios
Polyhydramnios is a medical condition describing an excess of amniotic fluid in the amniotic sac. It is seen in 0.2 to 1.6% of pregnancies,,...
. In an uncomplicated face presentation duration of labor is not altered. Perinatal losses with face presentation occur with traumatic version and extraction and midforceps procedures Duff indicates that the prevalence of face presentations is about 1/500–600., while Benedetti et al. found it to be 1/1,250 term deliveries.
Face presentations are classified according to the position of the chin
Chin
In the human anatomy, the chin is the lowermost part of the face.It is formed by the lower front of the mandible.People show a wide variety of chin structures. See Cleft chin....
(mentum):
- Left Mento-Anterior (LMA), Left Mento-Posterior (LMP), Left Mento-Transverse (LMT);
- Right Mento-Anterior (RMA), Right Mento-Posterior (LMP), Right Mento-Transverse (RMT);
Brow presentation
While some consider the brow presentation as an intermediate stage towards the face presentation, others disagree. Thus Bhal et al. indicated that both conditions are about equally common (1/994 face and 1/755 brow positions), and that prematurity was more common with face while postmaturity was more common with brow positions.Reasons for predominance of cephalic presentations
The piriform (pearPear
The pear is any of several tree species of genus Pyrus and also the name of the pomaceous fruit of these trees. Several species of pear are valued by humans for their edible fruit, but the fruit of other species is small, hard, and astringent....
-shaped) morphology of the uterus
Uterus
The uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...
has been given as the major cause for the finding that most singletons favor the cephalic presentation at term. The fundus
Fundus (uterus)
The fundus of the uterus is the top portion, opposite from the cervix.Fundal height, measured from the top of the pubic bone, is routinely measured in pregnancy to determine growth rates...
is larger and thus a fetus will adapt its position so that the bulkier and more movable podalic pole makes use of it, while the head moves to the opposite site. Factors that influence this positioning include the gestation
Gestation
Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time ....
al age (earlier in gestation breech presentations are more common as the head is relatively bigger), size of the head, malformations, amount of amniotic fluid
Amniotic fluid
Amniotic fluid or liquor amnii is the nourishing and protecting liquid contained by the amniotic sac of a pregnant woman.- Development of amniotic fluid :...
, presence of multiple gestations, presence of tumors, and others.
Two-thirds of all vertex presentations are LOA, possibly because of the asymmetry created by the descending colon
Colon (anatomy)
The colon is the last part of the digestive system in most vertebrates; it extracts water and salt from solid wastes before they are eliminated from the body, and is the site in which flora-aided fermentation of unabsorbed material occurs. Unlike the small intestine, the colon does not play a...
that is on the left side of the pelvis.
Diagnosis
Usually performing the Leopold maneuvers will demonstrate the presentation and possibly the position of the fetus. Ultrasound examinationMedical ultrasonography
Diagnostic sonography is an ultrasound-based diagnostic imaging technique used for visualizing subcutaneous body structures including tendons, muscles, joints, vessels and internal organs for possible pathology or lesions...
delivers the precise diagnosis and may indicate possible causes of a malpresentation. On vaginal examination, the leading part of the fetus becomes identifiable after the amniotic sac
Amniotic sac
The amniotic sac is the sac in which the fetus develops in amniotes. It is a tough but thin transparent pair of membranes, which hold a developing embryo until shortly before birth. The inner membrane, the amnion, contains the amniotic fluid and the fetus. The outer membrane, the Chorion,...
has been broken and the head is descending in the pelvis.