OB: Unit 4 Flashcards
Factors Affecting Labor: 5 P’s
1) passenger (fetus) 2) passageway 3) powers
4) position of the mother 5) psychologic (Crowder says physiologic in PP)
passenger
the way the fetus moves through the birth canal is determined by the following factors: size of fetal head; fetal presentation; fetal lie; fetal attitude; fetal position
*b/c the placenta must also pass through the birth canal, it can also be considered a passenger
anterior fontanel (size/shape/location); when does it close?
diamond shape - approx 3 cm x 2 cm - lies at junction of sagittal, coronal, and frontal sutures - closes by 18 months after birth
posterior fontanel (size/shape/location); when does it close?
triangular shape - approx 1 cm x 2 cm - lies at junction of sutures of the two parietal bones and the occipital bone - closes 6 to 8 weeks after birth
molding
slight overlapping of skull bones during labor - can be extensive, but most heads of newborns assume normal shape within 3 days after birth
presentation
refers to part of fetus that enters the pelvic inlet first and leads through the birth canal during labor
3 main presentations
1) cephalic 2) breech 3) shoulder
cephalic presentation
head first; occurs in 96% of births
breech presentation
buttocks, feet, or both first; occurs in 3% of births
shoulder presentation
seen in 1% of births
presenting part
the part of the fetus that lies closest to the internal os of the cervix - the part of the fetal body first felt by the examining finger during a vaginal examination
vertex
when the presenting part is the occiput
factors that determine the presenting part
fetal lie, attitude, and extension or flexion of the fetal head
fetal lie
the relation of the long axis (spine) of the fetus to the long axis (spine) of the mother
two primary lies
1) longitudinal (vertical): the long axis of the fetus is parallel with the long axis of the mother - present in more than 99% of term labors; either cephalic or breech presentation
2) transverse (horizontal or oblique): long axis of fetus is at right angle diagonal to long axis of mother
fetal attitude
the relation of the fetal body parts to one another - fetus assumes a characteristic posture (attitude) in utero partly b/c of the mode of fetal growth and partly b/c of the way the fetus conforms to the shape of uterine cavity
deviations from normal attitude may cause
difficulties in childbirth
fetal position
the relationship of a reference point on the presenting part (occiput, sacrum, mentum {chin}, or sinciput {deflexed vertex}) to the 4 quadrants of the mother’s pelvis - denoted by a three-part abbreviation
fetal position: three-part abbreviation
1) first letter denotes LOCATION of presenting part in right (R) or left (L) side of mother’s pelvis
2) second letter denotes the SPECIFIC presenting part of fetus (O = occiput; S = sacrum; M = mentum; Sc = scapula [shoulder])
3) final letter denotes LOCATION of presenting part in relation to portion of the maternal pelvis: anterior (A), posterior (P), or transverse (T)
EX: ROA = the occiput is the presenting part and is located in the right anterior quadrant of the maternal pelvis
EX: LSP = the sacrum is the presenting part and is located in the left posterior quadrant of the maternal pelvis
station
the relationship of the presenting fetal part to an imaginary line drawn between the maternal ischial spines and is a measure of the degree of descent of the presenting part of the fetus through the birth canal
station of presenting part
measured in centimeters above or below the ischial spines
EX: 1 cm above the ischial spines is noted as being minus (-) 1
EX: AT the level of the ischial spines, the station is said to be 0 (zero)
EX: 1 cm below ischial spines is noted as being plus (+) 1
engagement
term used to indicate that the largest transverse diameter of the presenting part has passed through the maternal pelvic brim or into the true pelvis and usually corresponds to station 0 - can be determined by abdominal or vaginal examination
passageway (birth canal)
composed of the mother’s rigid bony pelvis and the soft tissues of the cervix, pelvic floor, vagina, and introitus (external opening to the vagina)
four basic types of pelvis
gynecoid; android; anthropoid; platypelloid
