pelvic dimensions

Question 1

prognosis for successful vaginal delivery is dependent on

Answer 1

size and shape of bony pelvis
size of fetal head
force of UC
moldability of fetal head
presentation and position of fetus

Question 2

what are the four shapes of the pelvis

Answer 2

gynecoid (55%)
android (20%)
anthropoid (20%)
platypelloid (5%)

Question 3

pelvic outlet AP diameter

Answer 3

lower margin of symphysis pubis to the tip of the sacrum

11.5cm

Question 4

pelvic outlet transverse diameter

Answer 4

distance between the inner edges of the ischial tuberosities

11.5cm

Question 5

pelvic outlet posterior sagittal diameter

Answer 5

from the tip of sacrum to the line between tuberosities

7.5cm

Question 6

midpelvis

Answer 6

plane of least pelvic dimensions at the level of the ischial spines (0 station)

Question 7

midpelvis AP diameter

Answer 7

11.5cm

Question 8

midpelvis interspinous diameter

Answer 8

10cm

most important

Question 9

midpelvis posterior sagittal

Answer 9

4.5cm

Question 10

what causes joint relaxation in the last months of pregnancy

Answer 10

relaxin

Question 11

how can mom optimize pelvic size

Answer 11

squatting during pg
squatting, hands and knees during labor
pressure on SI joints during UC to open pelvis at the symphysis pubis

Question 12

what needs to be measured to estimate pelvic size at the inlet

Answer 12

the diagonal conjugate- should be greater than 11.5cm

Question 13

how do you measure the diagonal conjugate

Answer 13

patient in lithotomy position. Use 2 fingers in vagina, palpating the sacral surface while indenting the perineum to feel the tip of the sacral promontory. Then elevate hand until it contacts the pubic arch. Mark this point in your mind and withdraw your hand, measure length on your hand. Measurement should be greater than 11.5 cm. At this time, also palpate coccyx for mobility.

Question 14

how do you measure the midpelvis

Answer 14

check ischial spines (should be greater than 10cm) for prominence (difficulty finding them is a good sign of large width). Check for convergence of the side walls of the pelvis. Palpate with 2 fingers the curve of the sacrum. Shallow concavity of the scrum can be a sign of midpelvis contraction. If you can’t feel it, it is deep

Question 15

how do you measure the pelvic outlet

Answer 15

measure intertuberous diameter at the inner and outermost aspect. Use your fist b/t each ischial tuberosity. Should measure at least 8 cm. Measure the sub pubic arch, using the tips of the fingers and the pubic symphysis and the heel of each hand and the ischial tuberosities. The angle formed by the fingertips should be greater than 90 degrees. In measuring the posterior sagittal diameter, measure from the intertuberous line to the tip of the sacrum. Measurement should be at least 8 cm (not commonly done). Coccyx should be movable.