1. High frequency sound waves aimed at body tissues, deflected by tissues in their path, returned in echoes 2. Abdominal or transvaginal (1st trimester) 3. Cannot dx all malformations, never interpret a normal scan as a guarantee that the baby will be completely normal
What are 5 purposes of an US in the first trimester
What are the purposes of an US in the 2nd and 3rd trimester (7)?
1. Confirm viability 2. evaluate fetal anatomy 3. gestational age 4. multiples 5. biophysical profile 6. R/O previa, presentation 7. amniocentesis Costly and likely to require full bladder for visualization
What are the 2 disadvantages of US?
1. costly 2. may require a full bladder
Why are US more accurate in determining EDC in early gestation?
Less accurate as gestation increases
What is chorionic Villus Sampling (CVS) (7)?
1. 1st trimester alternative to amniocentesis 2. performed to determine fetal karyotype (genetics) 3. Transcervical (10-12 week)/transabdominal (must be at least 12 weeks) approach 4. Doesn't R/O all defects 5. fingerlike projections of the placenta that grow into the uterus 6. Takes 5-8 days for cells to grow in the lab 7. results are known earlier than amniocentesis
When can you perform CVS transcervical (TC)?
When can you perform CVS transabdominal (TA)?
must be at least 12 weeks
That is the advantage of CVS?
results known earlier than amniocentesis TC = 10-12 weeks TA = ≥12 weeks
That are the disadvantages of CVS?
1. fetal loss 0.6%-0.8% greater than amniocentesis 2. Limb anomalies 1-2%
What is an amniocentesis?
1. Aspiration of amniotic fluid from the amnitic sac, guided by US, to obtain fetal cells or other fetal products for analysis 2. 1st/2nd trimester = karyotype (genetic map) 3. 3rd trimester, evaluate lung maturity (surfactant levels), fetal bilirubin concentration 4. 1st 2ml discarded b/c contains mom's fluid 5. 20mL collected
What is the time frame for an early amniocentesis?
What is the time frame for a conventional amniocentesis?
What are the purposes of a 1st/2nd trimester amniocentesis (4)?
What are the purposes of a 3rd trimester amniocentesis (3)?
1. evaluate lung maturity (surfactant levels) * 2. fetal bilirubin concentration * (↑ means erythrocyte breakdown b/c of Rh antibodies in mother) 3. evaluate fetal condition when woman has Rh isoimmunization
What are the 2 advantages of amniocentesis?
1. experience 2. relatively painless
What are the 2 disadvantages of amniocentesis?
1. early loss rate (higher w/early) by infection or hemorrhage 2. may take 1-2 weeks for results
What is the safest karyotype procedure?
What are the maternal and paternal ages when amniocentesis is offered?
maternal >35 paternal >50
What is the pre-procedure care for an amniocentesis (2)?
1. informed consent. could be fetal loss, could be infection 2. establish stable mom and baby by taking VS
What is the post-procedure care for an amniocentesis (3)?
1. site observed for bleeding 2. show mom FHR & amniotic fluid to reassure mom all is ok right now 3. plan follow-up, set up appointment for her to find out results
What is percutaneous umbilical blood sampling (PUBS) & what is it used to diagnose (2)?
1. Cordocentesis- aspiration of fetal blood from the umbilical cord via US after 16 weeks 2. Used to dx Rh disease, rapid genetic studies, abnormal blood clotting factors (Hgb or platelet)
What are the risks of PUBS (2)?
1. 3-7% fetal loss rate 2. Morbidity high → puncture of umbilical artery, prolonged bleeding, cord laceration, hematoma, premature labor, blood sensitization, fetal bradycardia
What is a Nonstress test (NST) (5)?
1. Identifies whether an increase in FHR occurs when the fetus moves, indicating adequate oxygenation Reactive: 2. 24-28 weeks 50% non-reactive, medical decision when to do test considering the development of the fetus. 3. 28-32 weeks some sources use 10x10 rule 4. Reactive = 2 fetal heart accelerations w or w/o fetal movement within 20 min, peak at least 15x15. 5. Nonreactive = does not demonstrate required characteristics within a 40-60 min period. Fetus not getting enough O2.
What is a reactive NST?
2 fetal heart accelerations w or w/o fetal movement within 20 min, peak at least 15x15.
What is a nonreactive NST?
does not demonstrate required characteristics within a 40-60 min period. Fetus not getting enough O2.
What are 2 advantages of NST?
1. painless 2. noninvasive
What is the disadvantages of NST?
false positive test r/t sleeping fetus
What should not expect to see on a reactive NST strip?
Late decels, or any decals
What is Vibroacoustic stimulation (VAS) (4)?
1. Artifical larynx is applied to maternal abd. over fetal head & delivers 90 decibels of sound for 1-3 seconds. may be repeated 3x 2. Fetus is stimulated by the sound and more movement is noted 3. Reactive is 2 accels/10min (15x15 rule for accel) 4. Used to confirm nonreactive nonstress test results and to shorten time required to perform NST
What is a contraction stress test (CST) (3)?
1. Uterine contractions compress the arteries of the placenta, OCT records the response to the FHR to stress induced contractions 2. Fetus w/ adequate 02 reserves tolerates the temporary hypoxia-> reassuring HR 3. CST is more sensitive to fetal O2 reserves than NST so we can find & treat fetal hypoxemia in most instances.
What are the 2 methods to stimulate contractions in CST?
1. Breast stimulation 2. Oxytocin challenge test (OCT) = pitocin infusion, 2 contractions, each lasting 40-50 sec, occur in 10min. If decels are present DO NOT start Pitocin b/c O2 is already ↓ & Pit would make worse.
What are the 2 interpretations of CST?
1. Negative = adequate fetal 02. no decels, variability present, 7 day continued fetal well being provided mom stays stable 2. Positive = fetal hypoxemia. late decels accompanying at least 50% of contractions → immediate vigorous management=POISON
What is a biophysical profile (4)?
1. Most common fetal surveillance test for fetus experiencing high-risk pregnancy 2. Non invasive 3. Combination of NST & specific US evaluation → reflection of O2 status/sensitive to hypoxemia 4. Fewer false positives than NST & CST
What are the 5 criterion/scoring profile for BPP & what is a normal score?
1. NST (2 accels, pH 7.19) 2. Fetal breathing (pH 7.2) 3. Fetal movement (pH 7.1-7.2) 4. Fetal tone (pH 7.0) 5. Amniotic fluid volume (long term marker of fetal O2) 8-10 is NORMAL
nonreassuring = if fetal lungs mature, cervix favorable then deliver. If not, repeat in 24 hours
BPP scores of 0-2 & evaluation
BPP & oligohydramnios (3)
1. always means abnormal BPP 2. amniotic fluid index (AFI) ≤5 3. reflection of LT placental function
What is Nuchal translucency (3)?
1. use of US to see area behind neck at 10.5 to 14 weeks gestational age. Very specific window of time 2. the larger the area of nuchal translucency the more abnormal 3. all patients with abnormal results need further follow up
what is false negative?
the test is negative but the patient really has the condition
What is false positive?
the test is positive but the patient does not have the condition
What is sensitivity?
- patient has the condition and the test correctly identifies the patient has the condition. - High sensitivity is a good test
What is specificity?
patient doesn't have the condition and the test correctly identifies the patient does not have the condition