Which test to use? Nonstress test Biophysical profile, modified biophysical profile Contraction stress test Low incidence of unexpected fetal death Increase in time, cost and inconvenience Doppler velocimetry
Fetal Movement - Advantages Is a daily assessment Easy and Non-invasive Requires no special equipment Mom becomes more in tune with fetus and morelikely to recognize changes in behavior
Purpose of NST Determine if: Inadequate delivery of oxygen and/or nutrition infetal tissue Inadequate placenta exchange due to decreasedblood flow, decreased surface area or increasedmembrane thickness. Inadequate maternal nutrients or oxygen to theplacenta
Nonstress Test (NST) FHR accelerations reflect CNS alertness and activity(fetal well being) Absence of FHR accelerations may reflect CNSdepression caused by hypoxia, drugs, fetal sleep, orcongenital anomalies. The endpoint of the NST is the presence orabsence of FHR accelerations within a specifiedperiod of time
Performing the NST Position patient in semi-fowler or left lateral tilt (tominimize supine hypotension) Apply external monitors for contraction and FHRmeasurement Mark tracing when fetal movement is felt or heard Fetal sound stimulation may be used to elicit a response.
Nonstress Test (NST) Accelerations of the FHR occur with fetalmovement, uterine contractions, or in response toexternal stimuli.
Nonstress Test (NST) Target criteria is 2 accelerations of at least 15 beatsper minute (BPM) for 15 seconds in a 20-minuteperiod A healthy fetus < 32 weeks’ gestation may use atleast 2 accelerations of 10 beats per minute (BPM)for 10 seconds in a 20-minute period The more remote from term, the more likely thatnonreactivity will be due to fetal prematurity.
Interpreting the NST Reactive: Presence of at least 2 accelerations in a 20minute period Non reactive: FHR does not accelerate to meetcriteria or the fetus does not move May extend the testing period to 40 minutes or perform aback-up test. Reactive or Nonreactive with decelerations:individualize management
Biophysical Profile (BPP) Biophysical activities that can be recordedwith real time ultrasound: Fetal movement (FM) Fetal tone (FT) Fetal breathing movements (FB) Amniotic fluid volume (AFV, also known as AFI)
Biophysical Profile (BPP) Assessment of umbilical blood flow providesinformation on blood perfusion of thefetoplacental unit. Activities that become active first in fetaldevelopment (FT, FM) are the last to disappearwhen asphyxia arrests all activities. Activities that become active later in gestation(NST, FBM) will be abolished 1stin cases ofhypoxia and acidosis.
Biophysical Profile (BPP) - Scoring Each assessment When normal: 2 When abnormal: 0 Highest Score: 10, Lowest Score: 0 Accuracy improved by increasing the number ofvariables assessed. Overall false negative rate: 0.6/1000
Biophysical Profile (BPP) - Scoring NST: reactive – as described earlier. FBM: present - at least 1 episode of at least 30seconds duration (within a 30 minute period). FM: present - at least 3 discrete episodes. FT: normal - at least 1 episode of extension ofextremities or spine with return to flexion. AFV: normal – largest pocket of fluid greaterthan 1 cm in vertical diameter.
Purpose of Contraction Stress Test A hypoxic fetus will manifest late decelerationswhen uterine blood flow is compromised Late decelerations correlate with stillbirth, IUGR,and low Apgar scores.
Contraindications to CST PROM Previous classical cesarean delivery Placenta previa Incompetent cervix History of premature labor in this pregnancy Multiple gestation
Performing the CST Uterine contractions in excess of 30 mm Hgcreate an intrauterine pressure that temporarilystops uterine blood flow. A well oxygenated fetus has reserve to toleratecontractions Contractions for CST can be achieved through: Oxytocin challenge test (OCT) Breast (nipple) stimulation
Interpretation of the CST Negative: no late decelerations and adequate FHRrecording Positive: Late decelerations present with themajority of contractions (without excessiveuterine activity) Equivocal test results: Suspicious,hyperstimulation, unsatisfactory.
Doppler Flow Studies In Normal conditions the placenta offers littleresistance to fetal and maternal blood flow, evenduring diastole (i.e., between heart beats) Useful in evaluation and management of pregnanciescomplicated by conditions such as Suspected fetal growth restriction Red blood cell isoimmunization Pre-eclampsia
Doppler Flow Studies The most commonly assessed Doppler flowstudy of the fetus is the umbilical arterySystolic flowDiastolic flowNormal blood flow
Doppler Flow Studies Waveform may show decreased/absent diastolicblood flow in the umbilical vessels of a fetus Decreased/absent blood flow indicates that thefetus may not be receiving enough blood,nutrients, and oxygen from the placentaSystolic flow No endDiastolic flow