The fetal skull is the bony structure that houses the developing brain of the fetus. It is soft, flexible, and not fully ossified, allowing it to adapt to the birth canal during delivery.
✅ “The fetal skull is a flexible, partially ossified structure that plays a key role in labor, presentation, and molding during childbirth.”
| 🧱 Region | 📌 Description |
|---|---|
| Vault | Upper part; soft and compressible during labor |
| Base | Lower part; ossified and rigid, protects brainstem |
| Face | Front part; non-compressible (doesn’t enter birth canal) |
| 🦴 Bone | 📍 Number | 🔍 Location |
|---|---|---|
| Frontal bones | 2 | Forehead |
| Parietal bones | 2 | Sides of skull |
| Occipital bone | 1 | Back of skull |
Sutures are fibrous joints between bones that allow movement and molding during labor.
| ✨ Suture | 🧭 Location |
|---|---|
| Sagittal | Between the two parietal bones (midline) |
| Coronal | Between frontal and parietal bones |
| Lambdoid | Between occipital and parietal bones |
| Frontal (metopic) | Between two frontal bones (usually fuses post-birth) |
Fontanelles are membranous gaps at the junction of sutures that allow brain growth and skull compression.
| 💡 Fontanelle | 🧭 Location | 🧮 Shape & Closure |
|---|---|---|
| Anterior (Bregma) | Junction of sagittal, coronal sutures | Diamond-shaped; closes by 18 months |
| Posterior (Lambda) | Junction of sagittal, lambdoid sutures | Triangular-shaped; closes by 6 weeks |
| 📏 Diameter | 📍 Length | 🔍 Significance |
|---|---|---|
| Suboccipitobregmatic | 9.5 cm | Ideal presenting diameter in vertex presentation |
| Occipitofrontal | 11.5 cm | Larger; may cause difficulty in delivery |
| Mentovertical | 13.5 cm | Longest; seen in brow presentation |
| Biparietal | 9.5 cm | Widest transverse diameter of fetal skull |
✅ Suboccipitobregmatic (9.5 cm) is ideal for vaginal delivery.
🔹 Molding refers to the overlapping of fetal skull bones during labor to reduce the head size and allow passage through the birth canal.
🔸 Grade 0: Sutures separate
🔸 Grade 1: Sutures touch
🔸 Grade 2: Bones overlap but reducible
🔸 Grade 3: Bones overlap irreducibly (obstructed labor)
🔹 Determines fetal lie, attitude, presentation, and position
🔹 Assists in vaginal examination during labor
🔹 Aids in diagnosis of engagement and descent
🔹 Essential for identifying cephalopelvic disproportion
🟩 During Labor Assessment:
🔹 Palpate fontanelles and sutures per vaginal exam
🔹 Assess molding and station
🔹 Monitor fetal head descent and presentation
🟨 Documentation:
🔹 Record findings on partograph
🔹 Alert obstetrician if molding is severe or abnormal presentation
🟥 Education:
🔹 Teach mother about normal head shaping post-delivery
🔹 Reassure about closing fontanelles
🟡 Fetal skull vault is compressible; base is rigid
🟡 Anterior fontanelle = diamond; closes by 18 months
🟡 Biparietal diameter = 9.5 cm = widest transverse diameter
🟡 Molding allows fetal head to adapt to birth canal
🟡 Suboccipitobregmatic = ideal diameter for delivery
Q1. What is the shape of the anterior fontanelle?
🅰️ Oval
✅ 🅱️ Diamond
🅲️ Round
🅳️ Triangular
Correct Answer: 🅱️ Diamond
Q2. Which suture lies between the two parietal bones?
🅰️ Coronal
🅱️ Frontal
✅ 🅲️ Sagittal
🅳️ Lambdoid
Correct Answer: 🅲️ Sagittal
Q3. What is the ideal diameter for vaginal delivery?
🅰️ Occipitofrontal
🅱️ Mentovertical
✅ 🅲️ Suboccipitobregmatic
🅳️ Biparieto-mental
Correct Answer: 🅲️ Suboccipitobregmatic
Q4. Posterior fontanelle normally closes by:
🅰️ 1 year
🅱️ 9 months
✅ 🅲️ 6 weeks
🅳️ 18 months
Correct Answer: 🅲️ 6 weeks
Q5. Molding refers to:
🅰️ Skull ossification
🅱️ Fontanelle closure
✅ 🅲️ Overlapping of skull bones
🅳️ Brain development
Correct Answer: 🅲️ Overlapping of skull bones