The labor and birth process

what are some factors that influence the onset of labor?

uterine stretch, progesterone withdrawal, increased oxytocin sensitivity, increased release of prostaglandins

what are some premonitory signs of labor?

cervical changes (cervical softening, possible cervical dilation), lightening, increased energy level (nesting), bloody show, Braxton Hicks contractions, spontaneous rupture of membranes

What determines true labor?

regular, coming closer together; becomes stronger with time; starts in the back, radiates around towards the front of the abdomen, position changes don’t effect strength of contractions

What determines false labor?

irregular contractions not close together; weak, doesn’t get stronger or alternates between weak and not strong; usually felt in the front of the abdomen; may stop or slow down - walking may get contractions to go away

What are the critical factors affecting labor and birth (5 P’s)

passageway (birth canal, pelvis, and soft tissues), passenger (fetus and placenta), powers (contractions), position (maternal), psychological response

gynecoid

pelvis favorable for vaginal delivery

android

male shaped pelvis, not favorable

anthropoid

usually adequate pelvis

platypelloid

not favorable pelvis

cervix during labor

thins through effacement to allow presenting part to descend into vagina; baby won’t make it through passageway if cervix is not fully thinned

fetal skull

largest and least compressible structure; sutures, fontanelles, diameters

what are sutures?

allow for overlapping and changes in shape (molding); help identify position of fetal head

what are fontanelles?

intersections of sutures; help in identifying position of fetal head and in molding

what are the diameters of the fetal skull?

occipitofrontal, occipitomental, suboccipitobregmatic, and biparietal; depends on the fetal position

fetal attitude

relationship of fetal parts to itself; is the fetus in flexion and extension

fetal lie

relation of the spine of the fetus to the spine of the mother; longitudinal/vertical, transverse, oblique

fetal presentation

presentation is the part of the body that enters the pelvic inlet first; cephalic - head down, breech - feet first, shoulder

presenting part

part of the fetal body felt first on cervical exam

fetal position

the relationship of the presenting part to the four quadrants of the mother’s pelvis; side of the pelvis (R - right or L - left), presenting part (O - occipital, M - mental, Sa - sacrum, A - acromion), relation to anterior or posterior (A or P or T - transverse)

landmarks for fetal position

occipital bone (O): vertex presentation

chin/mentum (M): face presentation

buttocks/sacrum (S): breech presentation

scapula/acromion process: shoulder presentation

fetal station

relationship of the presenting part to an imaginary line drawn between the ischial spines

fetal engagement

engagement indicates that the largest transverse diameter or the presenting part has passed through the maternal pelvic brim into the true pelvis

what are the 7 cardinal movements that occur in a vertex presentation?

engagement and descent, flexion, internal rotation, extension, restitution, external rotation

what are primary powers?

uterine contractions (primary stimulus), involuntary, thin and dilate the cervix

what are secondary powers?

voluntary, intra-abdominal pressure from mother pushing and bearing down, three parameters: frequency, duration, intensity

what is the psychological response during labor influenced by?

background, coping mechanisms, support system, preparation for labor, socio-cultural influences, positive-negative influences

what are some physiologic responses to labor in the mother?

increased HR, CO, BP; increased WBC, increased RR and O2 consumption; decreased gastric motility and food absorption; decreased gastric emptying and gastric pH, nausea, vomiting, belching; endorphins euphoria, amnesia, elation, raises the pain threshold; paresthesia and difficulty voiding; muscle aches/cramps, decreased blood glucose levels, supine hypotension, increased BMR

what are some fetal physiologic responses to labor?

periodic FHR accelerations and slight decelerations, decrease in circulation and perfusion, increase in arterial carbon dioxide pressures, decrease in fetal breathing movements, decrease in fetal oxygen pressure; decrease in partial pressure of oxygen

what are some fetal heart rate responses to labor?

HR 110-160; provides information about oxygenation of the fetus and uteroplacental blood flow; responds to changes in PCO2, PO2 and other factors

what are some fetal cardiovascular responses to labor?

400mL of blood emptied from the uterus with each contraction; H/H very high to maximize oxygenation bc fetal circulation is not as good

what are some fetal respiratory responses to labor?

surfactant secretion stimulated by labor; clearance of fetal lung fluid by absorption prior to birth prior to labor; just prior to labor catecholamine surge contributes to the absorption of fluid; PO2 decreases, PCO2 increases, pH increases, HCO2 decreases, fetal respiratory movements decrease

what is the first stage of labor?

true labor to complete cervical dilation; longest of all stages; two phases - latent and active phase

what is the second stage of labor?

cervix 10 cm dilated to birth of baby

what is the third stage of labor?

birth of infant to placental separation; placental separation or placental expulsion