Fetal Skull, Diameters, and Birth Complications

Vocabulary flashcards covering fetal skull anatomy, diameters, presentations, moulding grades, and head swellings based on the lecture transcript.

Vertex

The part of the fetal skull lying between the anterior fontanelle (diamond-shaped) and the posterior fontanelle (triangular, above the occipital lobe).

Brow

The part of the fetal skull lying between the anterior fontanelle and the root of the nose.

Face

The part of the fetal skull lying between the root of the nose and the chin (mentum). It is the most common presenting part in anencephaly.

Anterior Fontanelle (Bregma)

A diamond-shaped gap between suture lines located at the junction of the frontal, sagittal, and coronal sutures.

Posterior Fontanelle (Lambda)

A triangular-shaped gap between suture lines located above the occipital lobe.

Occiput

Refers to the occipital bone of the fetal skull.

Sub-occiput

The region located below the occiput.

Mentum

Refers to the chin of the fetal skull.

Submentum

The region below the chin where the face and neck meet.

Vertical (Fetal Skull Terminology)

The highest point on the sagittal suture of the fetal skull.

Mento-vertical Diameter

The longest anteroposterior diameter of the fetal skull measuring $14\,\text{cm}$; seen in brow presentation and cannot pass the maternal pelvis, requiring a C-section.

Biparietal Diameter (BPD)

The most common engaging transverse diameter of the fetal skull, measuring $9.5\,\text{cm}$.

Sub-occipital Bregmatic Diameter

The engaging anteroposterior diameter measuring $9.5\,\text{cm}$, seen when the fetal head is fully flexed in a vertex presentation.

Occipito-frontal Diameter

An anteroposterior diameter measuring $11.5\,\text{cm}$, seen when the fetal head is deflexed in a vertex presentation.

Fetal Skull Diameters

The measurement lines used to assess engagement and passage through the maternal pelvis during labor.

Lightening

Relief from respiratory symptoms in pregnant women due to the descent of the fetal head into the maternal pelvis; occurs around $38\,\text{weeks}$ in primigravida and at the onset of labor in multigravida.

Moulding

The alteration of shape of the forecoming head while passing through the resistant birth passage during labor.

Grade 2 Moulding

Overlapping of fetal skull bones that can be easily separated, indicating cephalopelvic disproportion (CPD) and requiring a C-section.

Grade 3 Moulding

Fixed overlapping of fetal skull bones, indicating cephalopelvic disproportion (CPD) and requiring a C-section.

Caput Succedaneum

A collection of fluid or edematous swelling above the periosteum caused by prolonged stagnation of the head in one position during labor; it crosses suture lines, shows pitting on pressure, is present at birth, and disappears within a few hours.

Cephalhematoma

A collection of blood just below the periosteum resulting from traumatic instrumental delivery; it does not cross suture lines, lacks pitting on pressure, appears a few hours after birth, disappears in a few days, and is associated with skull bone fractures and jaundice.