Chapter 11: Antepartum Fetal Assessment Flashcards
Chorionic Villus Sampling (CVS)
is an invasive procedure that can be used to obtain a fetal karyotype (to screen for congenital defects; to see # of chromosomes)
-because the villi arise from the trophoblast cells, their chromosome structure is identical to that of the fetus
-performed between 10 and 12 weeks gestations
-results rapidly available
-using ultrasound guidance to locate the chorion cells, a thin catheter is inserted vaginally into the intrauterine cavity; an alternative technique involves abdominal or intravaginal insertion of a biopsy needle
-a small quantity of chorionic villi is then aspirated from the placenta
>Risks: infection, fetal loss, rupture of membranes, Rh isoimmunization, and possible fetal limb reduction
Percutaneous Umbilical Blood Sampling (PUBS)
invasive procedure that is performed to obtain a sample of fetal blood for karyotyping and to test for anemia, isoimmunization, metabolic disorders, and infection
-under ultrasound guidance, a needle is inserted through the maternal abdomen and into the fetal umbilical cord
>use of fetal blood sample for karyotyping allows for more rapid test results than when fetal skin cells are used, as with amniocentesis
-Complications: cord laceration, thromboembolism, PTL, PROM, and infection
Amniocentesis
invasive procedure that involves the removal of amniotic fluid
-under ultrasound guidance, a needle is inserted through the maternal abdomen and into the amniotic sac
-may be performed at the beginning at 12 weeks gestation
-components of the amniotic fluid, including fetal cells, may be analyzed for chromosomal abnormalities, fetal lung maturity, infection, and the presence of bilirubin in Rh-sensitized pregnancies
>later in pregnancy, amniotic fluid reduction (via amniocentesis) may be performed for temporary alleviation of maternal symptoms associated with hydramnios (excessive amniotic fluid)
>Complications: rupture of the membranes, PTL, infection, fetal injury, and fetal death
-if the woman is Rh(D)-negative blood, RhoGAM should be administered following amniocentesis to prevent isoimmunization
Amniocentesis also for Assessment of Lung Maturity
performed late in pregnancy
-Lecithin and sphingomyelin are the protein components of surfactant, the lung enzyme that is formed by the alveoli beginning around the 22nd week of gestation
>after amniocentesis, the lecithin/sphingomyelin ratio (L/S ratio) may be quickly determined by a “shake test” or sent to the lab for a quantified analysis
-a L/S ratio of 2:1, which occurs by 35 weeks gestation, is accepted as lung maturity (3:1 in infant of a diabetic mother)
>Phosphatidylglycerol and desaturated phosphatidylcholine are two other components that are found in surfactant after 35 to 36 weeks of gestation; because these two are present only with lung maturity, their presence in amniotic fluid sample is an indicator that respiratory distress syndrome will not occur in neonate
Amnioscopy
involve use of an amnioscope (small fetalscope) to visually inspect the amniotic fluid through the cervix and membranes
- performed to detect meconium staining
- carries risk of membrane rupture
Fetoscopy
method of visualizing the fetus with a fetoscope, an extremely narrow, hollow tube inserted through an amniocentesis technique
- used to assess fetal well being, obtain fetal tissue and blood samples, and perform fetal surgery, but not before 17 weeks of gestation
- risk of PTL and infection
Fetal Surgery
intrauterine surgery is performed to correct anatomical lesions such as myelomeningocele that, if left untreated, are associated with mortality/morbidity
-performed during second trimester before viability
-open fetal surgery involves uterine hysterotomy (opening of the uterus), surgical repair, and fetal replacement back into the uterus
>committed to cesarean births for this and all future pregnancies
>risk are PROM, PTL, and birth
