A cephalic presentation or head presentation or head-first presentation is a situation at

childbirth Childbirth, also known as labour and delivery, is the ending of pregnancy where one or more babies exits the internal environment of the mother via vaginal delivery or caesarean section. In 2019, there were about 140.11 million births globall ...

where the fetus is in a longitudinal lie and the

head A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aid in various sensory functions such as sight, hearing, smell, and taste. Some very simple animals may ...

enters the pelvis first; the most common form of cephalic presentation is the vertex presentation, where the

occiput The occipital bone () is a cranial dermal bone and the main bone of the occiput (back and lower part of the skull). It is trapezoidal in shape and curved on itself like a shallow dish. The occipital bone overlies the occipital lobes of the cereb ...

is the leading part (the part that first enters the birth canal). All other presentations are abnormal (

malpresentation In obstetrics, the presentation of a fetus about to be born specifies 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, bre ...

s) and are either more difficult to deliver or not deliverable by natural means.

Engagement

The movement of the fetus to cephalic presentation is called ''head engagement''. It occurs in the

third trimester Pregnancy is the time during which one or more offspring develops ( gestates) inside a woman's uterus (womb). A multiple pregnancy involves more than one offspring, such as with twins. Pregnancy usually occurs by sexual intercourse, but can ...

. In head engagement, the fetal head descends into the

pelvic cavity The pelvic cavity is a body cavity that is bounded by the bones of the pelvis. Its oblique roof is the pelvic inlet (the superior opening of the pelvis). Its lower boundary is the pelvic floor. The pelvic cavity primarily contains the reproducti ...

so that only a small part (or none) of it can be felt abdominally. The perineum and cervix are further flattened and the head may be felt vaginally. Head engagement is known colloquially as the ''baby drop'', and in natural medicine as the ''lightening'' because of the release of pressure on the upper abdomen and renewed ease in breathing. However, it severely reduces bladder capacity resulting in a need to void more frequently.

Classification

In the vertex presentation the head is flexed and the

leads the way. This is the most common configuration and seen at term in 95% of singletons. If the head is extended, the

face The face is the front of an animal's head that features the eyes, nose and mouth, and through which animals express many of their emotions. The face is crucial for human identity, and damage such as scarring or developmental deformities may aff ...

becomes the leading part. Face presentations account for less than 1% of presentations at term. In the sinicipital presentation the large

fontanelle A fontanelle (or fontanel) (colloquially, soft spot) is an anatomical feature of the infant human skull comprising soft membranous gaps ( sutures) between the cranial bones that make up the calvaria of a fetus or an infant. Fontanelles allow f ...

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 A breech birth is when a baby is born bottom first instead of head first, as is normal. Around 3–5% of pregnant women at term (37–40 weeks pregnant) have a breech baby. Due to their higher than average rate of possible complications for the ...

(3.5%) and the

shoulder presentation A shoulder presentation is a malpresentation at childbirth where the baby is in a transverse lie (its vertebral column is perpendicular to that of the mother), thus the leading part (the part that first enters the birth canal) is an arm, a shoulde ...

(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 The pelvis (plural pelves or pelvises) is the lower part of the trunk, between the abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also called bony pelvis, or pelvic skeleton). The ...

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 to the position of the

, both 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 its back anterior. In this position, the baby's chin is tucked onto its chest, so that the smallest part of its 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 Large for gestational age (LGA) is a term used to describe infants that are born with an abnormally high weight, specifically in the 90th percentile or above, compared to other babies of the same developmental age. Macrosomia is a similar term tha ...

anencephaly Anencephaly is the absence of a major portion of the brain, skull, and scalp that occurs during embryonic development. It is a cephalic disorder that results from a neural tube defect that occurs when the rostral (head) end of the neural tube fai ...

and other malformations,

cephalopelvic disproportion Cephalopelvic 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, an unfavorable orientation of the f ...

, and

polyhydramnios Polyhydramnios is a medical condition describing an excess of amniotic fluid in the amniotic sac. It is seen in about 1% of pregnancies. It is typically diagnosed when the amniotic fluid index (AFI) is greater than 24 cm. There are two clin ...

. In an uncomplicated face presentation duration of labor is not altered. Perinatal losses with face presentation occur with traumatic

version and extraction Version may refer to: Computing * Software version, a set of numbers that identify a unique evolution of a computer program * VERSION (CONFIG.SYS directive), a configuration directive in FreeDOS Music * Cover version * Dub version * Remix * ''Ve ...

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 The chin is the forward pointed part of the anterior mandible (List_of_human_anatomical_regions#Regions, mental region) below the lower lip. A fully developed human skull has a chin of between 0.7 cm and 1.1 cm. Evolution The presence of a we ...

(mentum): *Left Mento-Anterior (LMA), Left Mento-Posterior (LMP), Left Mento-Transverse (LMT) *Right Mento-Anterior (RMA), Right Mento-Posterior (RMP), 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 Postterm pregnancy is when a woman has not yet delivered her baby after 42 weeks of gestation, two weeks beyond the typical 40-week duration of pregnancy. Postmature births carry risks for both the mother and the baby, including fetal malnutrition, ...

was more common with brow positions.

Oskie presentation

The Oskie presentation is similar to the Occipito-Anterior position, where the baby is head down, facing the spine, with back on the ventral side of the uterus; however, in this position, while the torso is aligned with the mother's longitudinal axis, the legs of the fetus are extended straight along the frontal axis of the mother, as if the baby is creating a right angle with its body. For the Oskie position to occur the baby's head must be far down the pelvis in order to allow room for leg extension, typically the arms are bent, tucked against the baby's body. There are no known complications for labor and delivery. This presentation is rare and is not well researched.

Reasons for predominance

The piriform (

pear Pears are fruits produced and consumed around the world, growing on a tree and harvested in the Northern Hemisphere in late summer into October. The pear tree and shrub are a species of genus ''Pyrus'' , in the family Rosaceae, bearing the p ...

-shaped) morphology of the

uterus The uterus (from Latin ''uterus'', plural ''uteri'') or womb () is the organ in the reproductive system of most female mammals, including humans that accommodates the embryonic and fetal development of one or more embryos until birth. The uter ...

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 Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). It is typical for mammals, but also occurs for some non-mammals. Mammals during pregna ...

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 The amniotic fluid is the protective liquid contained by the amniotic sac of a gravid amniote. This fluid serves as a cushion for the growing fetus, but also serves to facilitate the exchange of nutrients, water, and biochemical products betwee ...

, 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 .

Diagnosis

Usually performing the Leopold maneuvers will demonstrate the presentation and possibly the position of the fetus. Ultrasound examination 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 The amniotic sac, also called the bag of waters or the membranes, is the sac in which the embryo and later fetus develops in amniotes. It is a thin but tough transparent pair of membranes that hold a developing embryo (and later fetus) until shor ...

has been broken and the head is descending in the pelvis.

Management

Many factors determine the optimal way to deliver a baby. A vertex presentation is the ideal situation for a vaginal birth, although occiput posterior positions tend to proceed more slowly, often requiring intervention in the form of

forceps Forceps (plural forceps or considered a plural noun without a singular, often a pair of forceps; the Latin plural ''forcipes'' is no longer recorded in most dictionaries) are a handheld, hinged instrument used for grasping and holding objects. Fo ...

, vacuum extraction, or

Cesarean section Caesarean section, also known as C-section or caesarean delivery, is the surgical procedure by which one or more babies are delivered through an incision in the mother's abdomen, often performed because vaginal delivery would put the baby or mo ...

. In a large study, a majority of brow presentations were delivered by Cesarean section, however, because of 'postmaturity', factors other than labour dynamics may have played a role. Most face presentations can be delivered vaginally as long as the chin is anterior; there is no increase in fetal or maternal mortality. Mento-posterior positions cannot be delivered vaginally in most cases (unless rotated) and are candidates for Cesarean section in contemporary management.

References

External links

{{DEFAULTSORT:Cephalic Presentation Obstetrics Presentations and positions in childbirth Midwifery