o
Estimation of fetal weight can be measured using the Loepold's maneuver, measuring fundal height, or
ultrasound biometry (the more methods used, the more accurate measurement)
-> Fetal Fibronectin (fFN)
o
It is a fetal glycoprotein produced by the trophoblast and other fetal tissues
o
The
absence of cervicovaginal fFN between 20 and 34 weeks gestation
has been shown to be a strong
predictor of a woman not experiencing preterm labor birth due to spontaneous preterm labor and
premature ROM.
o
Positive findings of this protein = birth within the net 2 weeks
o
Vaginal examinations, sexual intercourse within the previous 24 hours, vaginal creams, and some
medications can cause false findings --> should be AVOIDED prior to fFN testing
-> Evaluation of Fetal Lung Maturity
o
VERY IMPORTANT BEFORE BIRTH CAN PROGRESS!
o
The alveoli of the lungs are lined with
surfactant
(which is composed of phospholipids)
o
Surfactant is needed to maintain stability in the lungs by lowering the surface tension in
the alveoli
(the greater the surface tension, the harder it is to have adequate oxygen)
o
Lecithin/Sphingomylin Ratio
= two components of surfactant
Want
2:1 ratio
(usually seen at 35 weeks)–-> indicates that serfactin has been
released
When at least 2 times as much lecithin begins to exceed that of sphingomyelin is
found in the amniotic fluid, RDS is very unlikely
A delay is lung maturation
is often seen in infants with mother's that have
diabetes, nonhypertensive renal disease, or isoimmunization
Acceleration of lung maturity
can be seen with prolonged ROM (over 24 hours)
by approximately 1 week, therefore having a protective effect
L/S ratio results are NOT accurate when blood or meconium contaminates the
amniotic fluid
If preterm delivery is progressing:
o
Mom will get a shot of Betamethasone or Dexamethasone –
steroids to delay delivery by 24 hours or more so steroid has time
to work
o
Phosphatidyglycerol Levels (PG)
OB study guide
20
= The second most abundant phospholipid in surfactant
APPEARS at about 36 weeks gestation and increases in amount until term
May be present before 35 weeks in those with diabetes, PROM, vascular disease,
or sever preeclampsia
PRESENCE of this = low risk of RDS (absence = risk of RDS)
Useful in blood-contaminated specimens and vaginal specimens
o
Fluorescence Polarization
Measures the ratio of surfactant to albumin in uncentrifuged amniotic fluid
o
Shake Test and Foam Stability Test (ethanol, saline, amniotic fluid) -->shake x 15 sec...wait 15
minutes -->
some amniotic fluid is withdrawn and put it in a test tube with ethanol and saline. It is shaken
up and if a ring of bubbles occurs at the top of the fluid then it means there is surfactant in the amniotic
fluid.
o
-> Chorionic Villus Sampling (CVS)
-Detects genetic, metabolic, and DNA disorders in the
1
st
trimester (between 8-12 weeks
= when the villi is present)
--> Benefit is this is done early in case parents are potentially considering
termination if a problem exists
-->
Obtains a small sample of chorionic villi from edge of placenta.
