Antenatal testing Flashcards
what is the goal of antenatal testing?
to prevent fetal death
are abnormal antenatal testing results reliable? what does this predict?
no
predicts wellness, not illness
what are the modalities of antenatal testing?
- fetal movement assessment
- nonstress test
- contraction stress test
- biophysical profile
- umbilical artery doppler velocimetry
- middle cerebral artery doppler velocimetry
the fetal nonstress test is based on what premise?
HR of a fetus that is not acidotic or neurologically depressed will temporarily accelerate with fetal movement
what is a good indicator of normal fetal autonomic function?
fetal heart reactivity
what is umbilical dopper US used to assess?
hemodynamic components of vascular impedence
how is umbilical flow velocity of a normal fetus characterized?
high velocity diastolic flow
in IUGR what happens to the umbilical artery diastolic flow?
decrease
how is IUGR screening done on PE and biochemical profile?
- PE: maternal uterine fundal height
- biochemical: unexplained MSAFP raises risk of IUGR
who needs antenatal testing?
- preexisting insulin requiring diabetics
- previous history of intrauterine fetal demise
- post-dates pregnancies (over 41 weeks)
- chronic HTN
- decreased fetal movement
what is fetal monitoring used to evaluate?
intrapartum fetal oxygenation
is fetal monitoring diagnostic or screening?
screening
when is external monitoring done?
clinically undesirable or impossible to rupture membranes
what is required for internal monitoring? why?
- requires rupture of membranes / amniotomy
- need to place electrodes on fetus’ scalp
what does a tocodynamometer detect? what does it record?
- detects alterations in the curvature of the abdomen resulting from changes of the contracting uterus
- accurately records frequency and duration of contractions, but not amplitude
what does an intrauterine pressure catheter measure? when is it used?
- measures pressure readings that indicate onset, strength (amplitude), and duration of contractions
- inserted after ROM
what is tachysystole in terms of uterine contractions?
over 5 contractions in 10 m averaged over 30 m
the fetal baseline HR varies between what values?
110-160 bpm
when should you look at FHR?
between contractions
what is one of the best indicators of intact integration between CNS and HR of the fetus?
normal FHR variability
what does normal FHR variability indicate?
intact integration between CNS and HR of the fetus
at what week does a fetus produce normal variability in HR?
28 weeks
loss of FHR variability indicates what condition?
fetal hypoxia
what are the three primary mechanisms by which uterine contractions can cause a decrease in FHR?
COMPRESSION OF:
- fetal head
- umbilical cord
- uterine myometrial vessels
what is the term for when FHR changes are associated with contractions?
periodic
what is the term for when FHR changes are NOT associated with contractions?
nonperiodic
what two mechanisms alter FHR?
- reflex response secondary to nervous control of the heart by direct nervous innervation or by humoral control of the ANS
- transient slowing of the heart when fetal myocardial hypoxia is present
what is the morphology of early deceleration?
visually apparent, usually symmetrical gradual decrease and return of the FHR with a contraction, OR a MIRROR IMAGE of the contraction
what is the cause of early deceleration?
vagal stimulation from head compression
what is the cause of transitory decreases in HR (late decelerations)?
uteroplacental insufficiency
what is variable deceleration? what is the cause?
reflex change mediated by the vagus nerve generally caused by umbilical cord compression
moderate FHR variability reliably predicts the absence of what process?
metabolic acidemia
does intrapartum interruption of fetal oxygenation result in neurologic injury? what is the exception?
no
unless it progresses to the stage of significant metabolic acidemia
