Fetal Skull Anatomy

Question 1

Supraoccipitomental diameter

Answer 1

13.5cm
Brow presentation
Vertex to chin
AP in Brow
Longest AP presentation
Cannot deliver

Question 2

9.5cm diameter presentation

Answer 2

Supraoccipitobregmatic diameter

Undersurface of occipital bone at junction with neck to centre of anterior fontanelle ; presenting AP diameter when the head is well fixed

Submentobregmatic diameter

Extends from junction of neck & lower jaw to the centre of anterior fontanelle; presenting AP diameter in face presentation

Question 3

Submentobregmatic

Answer 3

Face presentation
Mentoanterior can deliver
Mento posterior cannot deliver

Question 4

Military presentation

Answer 4

Moderate flexion

Question 5

Brow presentation

Answer 5

Poor flexion

Question 6

Face presentation

Answer 6

Full extension

Question 7

Diagonal conjugate diameter of brim

Answer 7

From sacral promontory to under border of symphysis pubis

Question 8

Anterior posterior diameter of outlet

Answer 8

Under body of symphysis pubis to end of sacrum or coccyx if fused

Question 9

Inclination of pelvic brim

Answer 9

50-60 degrees
Usually 55 degrees

Question 10

True conjugate of brim

Answer 10

From sacral promontory to upper and inner border of symphysis pubis

Question 11

OVD : which instrument to use
Mid cavity

Answer 11

0-+1

Question 12

+2 - +3

Answer 12

Low cavity

Question 13

+4 +5

Answer 13

Outlet

Question 14

Contraindications to vacuum birth

Answer 14

Avoid < 32 weeks gestation

Use with caution 32-36 weeks

Question 15

Indications of forceps in theatre

Answer 15

OP / OT position

BMI > 30

EFW > 4kg

Mid cavity forceps