Chapter 12 Amniotic Fluid Flashcards
Liquid product of fetal metabolism
Amniotic fluid
Amniotic fluid is present in the
Amnion
Membrane that surrounds the fetus
Amnion
What is the purpose of the sac (5)
- Provides a protective cushion
- allows fetal movement
- stabilizes the temperature to protect fetus from extreme temperature changes
- permits proper lung development
- allows for exchange of water and chemicals
What is tested to determine if C-section can be performed
Lung development
Label
Reasons one might have an amniocentesis performed at 14-18 weeks (5)
- Being 35 or older; risk of birth defects/Down syndrome
- having a previous child or pregnancy with a birth defect
- abnormal blood triple or quadruple screening (AFP)
- family history of genetic disorders (cystic fibrosis, tay-sachs, sickle cell, hemophilia, Huntington chorea, muscular dystrophy)
- > 3 miscarriages
Reasons one might have an amniocentesis performed past 20 weeks (2)
- Fetal lung maturity
- fetal distress: HDN or infection
How is amniotic fluid formed
First produced by amnion and placenta. Then fetus plays active role to balance composition and production
Mechanism involved with balancing amniotic fluid (4)
- Intestinal absorption following fetal swallowing of fluid
- Capillary exchange in pulmonary system as alveoli of fetal lungs develop
- water and electrolytes removed and replaced by products of fetal urination
- maternal exchange remove waste products and adds water, nutrients and electrolytes
Variation of what 3 things indicate fetal distress
Fetal urine, lung fluid, and maternal circulation
During first thmester approx. 35mL of amniotic fluid is derived from
Maternal circulation
At 37 weeks ammotle fluid peak at 800 to 1200mL. Increased urine is regulated by
Fetal swallowing
Lung fluid adds what to amniotic fluid to measure lung maturity
Lung surfactants
Excess amniotic fluid from failure of fetus to swallow >1200 mL
Polyhydramnios
Polyhydramnios cause
Neural tube disorders, structural/chromosomal abnormalities, cardiac arrhythmias, infections
Decreased amniotic fluid from increased fetal swallowing, membrane leakage <800 mL
Oligohydramnios
Oligohydrammos causes
Umbilical cord compression
Amniotic fluid composition
Similar to maternal plasma with sloughed fetal cells
Amniotic fluid contains biochemical substances produced by fetus such as (9)
Bilinibin, lipids, enzymes, electrolytes, urea, creatinine, uric acid, proteins, hormones
Fetal urine increases (3)
Creatinine, urea, uric acid
Fetal age can be estimated by
Creatinine
Age when creatinine level is 1.5 to 2.0 mg/dL
<36 weeks
Age when creatinine level is >2.0
> 36 weeks
Needed to determine premature membrane rupture or accidental puncture of maternal bladder from amniocentesis
Maternal urine vs. amniotic fluid
<3.5 mg/dL creatinine and <30 mg/dL urea
Amniotic fluid
Values as high as 10 mg/dL for creatinine and 300 mg/dL for urea
Urine
The presence of glucose, protein, or both is associated more closely with
Amniotic fluid
Maternal urine vs. Amniotic fluid measure
Creatinine, glucose, protein, urea
Specimen air dries on glass slide; examine microscopically for “fern-like” amniotic fluid crystals
Fern test
How is an amniocentesis collected
Needle aspiration into amniotic sac under ultrasound guidance: transabdominal or vaginal
When should an amniocentesis be collected and how much
No more than 30 mL after 14th week of gestation
How should samples be stored for testing
Keep at room temp and separate cells for genetic testing. Place on ice and refrigerate for fetal/lung FLM tests. Protect from light for bilirubin testing (HDN)
Centngage or filter fluid only for what test
Fetal lung maturity (FLM) tests
Color for normal appearance
Colorless to very pale yellow
Color for traumatic tap, abdominal trauma, intra-amniotic hemorrhage
Blood-streaked
Color for bilirubin present, hemolytic disease newborn (HDN)
Yellow to amber
Color for meconium (fetal bowel movement)
Dark green
Color for fetal death
Dark red-brown
Tests for neural tube defects (4)
- Alpha-fetoprotein (AFP) produced by the fetal liver prior to 18 weeks gestation
- increased levels in maternal blood or amniotic fluid indicate possible anencephaly or spinal bifida
- increased levels are found when skin fails to close over neural tissue
- measure maternal blood first, then amniotic fluid
What happens to a mom that has 2 babies with Rh+ blood while she has Rh-
First pregnancy= fetal blood enters maternal circulation and Rh antibodies form
Second pregnancy= Rh antibodies destroy fetal Rh+ RBCs
Most common complication of early delivery
Respiratory distress syndrome (RDS)
Lack of lung surfactant keeps
The alveoli open during inhaling and exhaling
Decreases the surface tension on the alveoli so the lungs can inflate more easily
Surfactant
Amniotic fluid bilirubin measured in spectrophotometric instrument for activity at 450 OD tests for
Hemolytic disease newborn (HDN)
Alpha-fetoprotein (AFP) increase tests for
Neural tube defects: anencephaly and spinal bifida. Also possibility of multiple pregnancy
Surfactant measurements: - lecithin-sphingomyelin ratio (L/S) - phosphatidyl glycerol - foam shake test - microviscosity decrease - lamellar bodies Test for
Determination of fetal lung maturity (FLM) for respiratory distress syndrome (RDS). L/S ratio >2.0 is desirable
Represent a storage form of surfactants responsible for FLM
Lamellar phospholipids
Lamellar phospholipids are produced and secreted by
Type II pneumocytes of the fetal lungs
Amniotic fluid lamellar bodies are measured by
Automated cell counters using the platelet methodology
A count of greater than 32,000 lamellar bodies represents
Adequate fetal lung maturity
Range of lamellar bodies in 3rd trimester
50,000 to 200,000
Produced by the placenta and acts as the glue that attaches the placenta to the uterine wall. Also acts as a lubricant aiding in the passage of the newborn through the vaginal canal
Fetal fibronectin
What kind of collection detects fetal fibronectin
Cervicovaginal
Fetal fibronectin can be used to predict
Pre-term delivery
