Labour and Birth Process Flashcards
5 P’s affecting the process of birth and labour
passenger (fetus and placenta) power (contractions) passageway (birth canal) position of the mother psychological response
passenger (fetus and placenta)
movement of fetus through birth canal determine by several factors:
size of fetal head - palpation of fontanels after rupture of membranes can determine fetal position, presentation and attitude
fetal presentation - part of the fetus that enters the pelvic inlet first and leads through the birth canal during labour. 3 main presentation; cephalic (head first), shoulder, and breech (buttocks first)
fetal lie - relation of the long axis (spine) of the fetus to the long axis (spine) of the mother. 2 primary lies, transverse - in which the spine of the fetus is a right angle to the spine of the mother - or longitudinal - in which the spine of the fetus is parallel to the spine of the mother. vaginal birth cannot occur when fetus in transverse lie
fetal attitude - relation of the fetal body parts to one another. normal fetal attitude is termed general flexion (spine curved, limbs pulled into body, head titled to chest). biparietal diameter is largest transverse diameter and indicator of fetal head size (normally 9.25cm at term)
fetal position - position is the relationship of reference on the presenting part to the four quadrants of the mother pelvis. 3 letter abbreviation - L or R to determine if fetus on left or right side of pelvis, middle letter is specific presenting part of the fetus (O for occiput, S for sacrum, M for mentum (chin), and Sc for scapula (shoulder)), last letter is the location of the presenting part in relation to A anterior, P posterior, or T transverse portion of the pelvis. Station - position of the fetal presenting part in relationship to the birth canal (-1, 0, +1). Engagement - indicates presenting fetal part has passed through the pelvic brim into the inlet of the true pelvis (station 0), often occurs in the weeks before labour begins
Placenta rarely impeded vaginal birth expect in placenta previa (placenta blocking cervical os)
passageway (birth canal)
composed of bony rigid pelvis and soft tissue of cervix, pelvic floor, vagina and external opening of vagina (introitus)
bony pelvis divided into false pelvis and true pelvis, true pelvis involved in labour, false pelvis part above brim and not involved in labour.
passageway - true pelvis
divided into inlet or brim; midpelvis or cavity; and outlet
pelvic cavity varies in shape and size; four basic types of pelves. mixed types of pelvis more common than pure types.
passageway - soft tissue
uterus compromised of uterine body (corpus) and cervix (neck). after labour begins contractions cause the uterine body to have a thick muscular upper segment and a thin passive lower segment, separated by the physiological retraction ring. lower segment distends to accommodate the upper segment contents as the walls of the upper segment thicken reducing its accommodating capacity. each contraction exerts downward pressure on the fetus pushing it against the cervix which thins (effacement) and dilates. once the fetus descends into the cervix, the cervix is pulled up and back to allow it to pass through. pelvic floor separates the pelvic cavity from the perineal space, allowing the fetus to rotate anteriorly as it passes through.
comparison of pelvic types
gynecoid (classic female type) - slightly ovoid or transversely rounded brim, moderate depth, straight side walls, blunt and somewhat widely separated ischial spine, deep and curved sacrum, wide subpubic arch, usual mode of birth is vaginal, spontaneous in occipitoanterior position
android (resembling male pelvis) - heart shaped and angulated brim, deep depth, convergent side walls, prominent and narrow ischial spine, slightly curved sacrum with the terminal portion beaked, narrow subpubic arch, mode of birth C section, vaginal, difficult with forceps
anthropoid (resembling anthropoid ape pelvis) - oval brim - wider anteroposteriorly -, deep depth, straight side walls, prominent ischial spine, slight curved sacrum, narrow subpubic arch, mode of birth vaginal, forceps or spontaneous, occipitoposterior or occipitoanterior position
platypelloid (flat pelvis) - flattened anteroposteriorly brim - wide transversely -, shallow depth, straight side walls, blunt and widely separated ischial spine, slightly curved sacrum, wide subpubic arch, mode of birth vaginal and spontaneous
powers (contractions)
involuntary (contraction) and voluntary (pushing) powers work to expel the fetus and placenta.
primary powers - involuntary uterine contraction. signal start of labour. describe contractions using frequency, intensity, and duration. responsible for effacement and dilation of cervix. use of analgesia can decrease duration and frequency of contractions resulting in longer active phase of first and second stage of labour
secondary powers - bearing down from mother. starts once cervix has dilated (marks end of first stage of labour). Ferguson reflex - release of oxytocin that triggers mothers need to bear down.
signs preceding labour
lightening or dropping - when fetus presenting part descends into the true pelvis. results in return of urinary frequency due to bladder compression and ease of breathing due to less pressure in diaphragm
bloody show - bloody tinged or brownish cervical mucus
in days preceding labour: loss of 0.5 to 1.5kg caused by water loss from electrolyte shifts that in turn produce changes in estrogen and progesterone levels, surge of energy (nesting), braxton hicks contractions
stages of labour
normal labour of a fetus in vertex position consists of regular progression of contractions, effacement and dilation of cervix, and progress in descent of the presenting part
four stages of labour:
first stage - from onset of regular uterine contraction to full dilation of cervix. parity has strong effect in length of first stage. first stage last longer than third and second combined. divided into latent (effacement progression of cervix little increase in descent) and active (rapid dilation of cervix and increased rate of descent) labour
second stage - time of full dilation of cervix to expulsion of fetus. composed of latent (passive descent of fetus and rotation to anterior position in birth canal) and active (pushing) phase
third stage - birth of fetus to placental delivery. normally three or four more contractions for placental delivery. no more than 1 hour
fourth stage - arbitrary last 2 hours after placental delivery. immediate recovery period
mechanism of labour
7 movements of the mechanism of labour
engagement - when biparietal diameter of head in inlet of pelvis, said to be engaged. head normally engages in pelvis in synclitic position (parallel to anteroposterior plane of pelvis) frequently asynclitism occurs (head deflected anterior or posterior in pelvis) to accommodate decent through pelvic cavity. extreme asynclitism can result in inability to descend
descent - descent depends on pressure exerted by amniotic fluid, direct pressure exerted by contracting fundus, force of contraction of maternal diaphragm and abdominal muscles, and extension and straightening of the fetal body. degree of descent measured by station of presenting part.
flexion - as soon as descending head meets resistance from cervix, pelvic wall, or pelvic floor, it flexes so chin is brought closer to fetal chest
internal rotation - maternal pelvic inlet widest in transverse diameter but outlet widest in anteroposterior diameter, in order for fetus to exit the head must rotate to accommodate the birth canal changes.
extension - when fetal head reached perineum for birth it passes under the lower border of the symphysis pubis first and the head emerges by extension
external rotation - after head is born it rotates briefly to position it occupied when engaged in the inlet (referred to as restitution). the turn realigns infant head with back and shoulders.
birth by expulsion - expulsion of the rest of the infants body ending the second stage of labour
fetal adaptation
FHR - temporary acceleration and slight decelerations of FHR expected in response to spontaneous fetal movement, vaginal examination, fundal pressure, contractions, abdominal palpation, and fetal head compression
fetal circulation - contractions tend to decrease circulation, healthy fetus can compensate for this stress and exposure to increased pressure while moving passively through birth canal
fetal respiration - fetal lung fluid cleared from air passage as infant passes through canal, fetal oxygen pressure decreases, arterial carbon dioxide pressure increases, arterial pH decreases, bicarbonate levels increase, fetal resp movements decrease during labour
