Basic OB
Prenatal Diagnostic Tests
Chapter 16 lecture
Ultrasound
Transvaginal
Done during the first trimester to determine pregnancy,
confirm fetal viability, estimate gestational age, determine number of
fetuses, and in conjunction with other tests.
Transabdominal
Done during the second and third trimesters to assess above
components plus to evaluate fetal anatomy, assess progress of fetal
growth, evaluate amniotic fluid volume, and determine presentation and
location of cord and placenta.
Advantage is that it is noninvasive and disadvantages are that it is
expensive and cannot detect all fetal anomalies.
Alpha-fetoprotein screening
Measures AFP in maternal serum and in amniotic fluid. See box 162 for conditions associated with abnormal levels. Evaluated between 16
and 18 weeks usually through maternal serum. Advantages include
minimal invasiveness and is inexpensive. Limitations include that it is a
screening test and abnormal results must be followed by more tests. It is
also very time sensitive so screening outside of the 16-18 week window
offers inaccurate results and benign conditions can cause abnormal
readings.
Triple-marker screening
In addition to MSAFP, hCG and unconjugated estriol are added to
screen for chromosomal abnormalities.
Chorionic Villus Sampling
Samples of chorionic villus cells can be used for diagnosis of fetal
chromosomal, metabolic, or DNA abnormalities between 10 and 12 weeks
gestation. Indicated only for those at high risk for genetic anomalies.
Procedure
CVS can be performed by a transcervical (catheter inserted
through the cervix) or a transabdominal (needle inserted through the
abdomen) approach. The advantage is that this is performed early in the
pregnancy, allowing for a first trimester abortion if the results are
abnormal (for those who would consider an abortion as an option). The
disadvantages are a higher pregnancy loss rate than with amniocentesis, a
higher limb reduction rate in CVS performed before 10 weeks, and the
possibility of Rh sensitization.
Amniocentesis
Aspiration of amniotic fluid and can be performed in the 2nd or 3rd
trimesters. See Box 16-3 for common indications.
Procedure
Using US to locate the fetus and placenta, a needle is
inserted into the largest pocket of fluid and fluid is withdrawn for
analysis. The mother will then be monitored for UC and FHT for the
next ½ to 1 hours. Advantages include low fetal loss rate while
permitting diagnosis of many anomalies. Also used to determine fetal
lung maturity. Disadvantages include later diagnosis than with some
other methods and slight risk of spontaneous abortion.
Nonstress test (NST)
This assesses fetal heart tones for accelerations, especially those
associated with fetal movement. Accelerations are associated with
adequate oxygenation and a healthy nervous system.
Procedure
The woman is monitored for UC and FHT. She may also be
instructed to “mark” any fetal movement. A reactive strip is one that
occurs during a 20 minute period in which the fetal heart rate goes
above baseline twice by at least 15 bpm and for at least 15 seconds.
Nonreactive strips do not meet this criteria…see figure 16-8. Advantages
include noninvasiveness and may be repeated daily. A disadvantage is a
false positive due to fetal sleep but this can be corrected by prolonging
the test for at least 40 minutes.
Contraction Stress test
If the fetal oxygenation appears marginal during the NST,
contractions may be added to measure the response to stress. Late
decelerations, or those where the fetal heart rate decreases after the
contraction peaks and doesn’t return to baseline until after the
contraction has ended, suggest inadequate oxygen reserves,
Procedure
Either IV pitocin or nipple stimulation is used to produce at
least three contractions of 40 seconds duration within a 40 minute
period. The fetal heart rate pattern is then interpreted. Advantages are
few, disadvantages include hyperstimulation of the uterus, time required,
and expense.
Biophysical Profile
This test assesses five parameters of fetal well being: NST, fetal
breathing movements, gross fetal movements, fetal tone, and amniotic
fluid volume. See table 16-1 for interpretation. This is a frequently used
test due to low cost and high sensitivity.
Percutaneous umbilical blood sampling
Aspiration of fetal blood from the umbilical cord. Disadvantages
include fetal loss and premature labor.
Maternal Assessment of Fetal Movement (Kick counts)
This is the easiest method to evaluate fetal wellbeing. Like an
infant, the fetus has sleep/wake cycles and the mother is usually aware of
these. The mother is instructed to count kicks or fetal movements
during a time that the fetus is normally active. The duration is usually
for an hour and the mother can make comparisons from day to day.
Obviously a significant decrease in kicks should be reported to the
healthcare provider along with a significant increase (an increase
precedes a decrease in some situations).
Giving Birth
Chapter 17 lecture
S/S of labor
Lightening
Increased level of activity
Braxton Hicks Cx
Cervical ripening
UC
Show
ROM
Components of labor
spines
Fetal presentation
Engagement
Widest part of fetus is at the level of the ischial spines
“0” station
Station
Relationship of the presenting part to the ischial
Ranges from -2 to +2
+3 to +4 is on the perineum
Fetal lie
whether the fetus is in a horizontal or vertical position
cephalic presentation
breech
shoulder
Fetal positions pgs 348, 349, & 350
Powers of labor
UC
Increment, acme, and decrement
Contour changes…Bandl’s ring
Pushing
Stages of labor
First stage (begins with true labor and ends with full dilation/effacement)
Latent (up to 3cm)
Active (4-7cm)
Transition (8-10cm)
Second stage (complete-birth)
Third stage (birth-expulsion of placenta)
Placental separation
Placental expulsion
Fourth stage (recovery, 1-4 hours)
Assessment in labor
Early
Leopold’s maneuvers
ROM
If membranes spontaneously ruptured prior to
admission, the time is determined. Whether artificially ruptured or
spontaneously, the color and quality of the fluid is assessed. Clear is
good and may have bits of a creamy white substance (vernix). Fluid
should have no odor. Yellow fluid and foul odor suggest infection.
Green fluid with or without chunks suggest fetal distress. ROM also
ends the mother’s ability to get up and walk unless the presenting part is
well-engaged.
SVE
VS
Labs
UC
Length, intensity, frequency
Effacement
Dilatation
External vs. internal monitoring
Care of the woman during the first stage of labor
Keep bladder empty
Change linens, gowns frequently
Pain mgmt
Support people
Care of the woman during the second stage of labor
Laboring down
Med mgmt
Delivery table setup/prep
Positioning
Pain mgmt
Pushing
Episiotomy
Birth
Cutting and clamping the cord
Care of the woman during the third and fourth stages of labor
Placenta delivery
Perineal repair
Oxytocin
Recovery assessment
Newborn care in delivery room
After cord is clamped, if baby looks good, mother may hold
momentarily, then baby is taken to radiant warmer, dried off quickly and
towel discarded, hat applied, bracelets applied to wrist, foot, and
mother’s arm. Footprints taken along with mother’s thumb print…all
before mother and baby are separated. Baby suctioned and possibly deep
suctioned if not establishing respirations.
Newborn assessment in the delivery room
Apgar
Pg. 385
Done at 1 and 5 minutes
Not used to determine need for resuscitation, NALS for
that
Vital signs
TPR, bp not routine unless cardiac abnormality suspected
Cord is assessed for vessels
Voids and stool assessed
If baby is doing well, may stay up to one hour with mother before going to
nursery but temp evaluated often