Prenatal Genetic Workup

AMA

advanced maternal age of 35 or greater at delivery

indications for prenatal genetic testing

AMA

family hx of abnormalities

prior pregnancy w abnormalities

maternal diabetes

prenatal exposure to noxious substances

triad of diagnostic prenatal testing

maternal serum markers (blood tests)

invasive procedures (amnio, CVS)

OB us/1st trimester

maternal serum testing

goal is to ID variations in pregnancy

quad screen on single sample of blood is normal test done now

gestational age importance

accurate dates needed or test results can be falsely positive or negative

AFP (Alpha-Fetoprotein)

glycoprotein produced by conceptus fetal liver, yolk sac & developing fetal GI tract

found in amniotic fluid

very critical to have accurate dating for these results

high AFP

incorrect gestational age

multiple gestations

open neural tube defects

open abdominal wall defects

esophageal & duodenal atresia

low AFP

trisomy 21 (downs)

trisomy 18 (edwards)

trisomy 13 (patau)

human chorionic gonadotropin (beta-hCG)

not produced by conceptus, from trophoblastic cells in developing placental tissue

estriol

one of 3 primary types of estrogen

reduced levels are strongest indicator of trisomy 18

amnio tests performed

biochemical assay: detects open neural defects

chromosomal analysis: detects chromosome abnormalities

karyotype

single-gene disease

complete set of chromosomes (23 sets)

medical conditions arising from a single gene

aneuploidy

autosomal recessive disorder

autosomal dominant disorder

abnormal # of chromosomes

defective copy of gene from each parent

only 1 defective gene required to cause disease

x-linked disease

triploidy

trisomy

most are recessive, female has 1 normal & 1 defective X chromosome

presence of 3 chromosomes karyotype (total of 23 sets but 69 chromosomes)

presence of 3 chromosomes on specific set (ex: trisomy 18 is 3 on 18th chromosome)

disomy

monosomy

tetrasomy/pentasomy

2 copies of chromosome from 1 parent (not normal)

lack of 1 chromosome of normal complement

presence of 4 or 5 copies of chromosome

amniotic band syndrome

constricting bands of amniotic tissue

early rupture of amniotic membrane

lack of fusion b/w chorion & amnion

sirenomelia

AKA mermaid syndrome

fused lower limbs

ellis-van creveld syndrome

amish community

rare type of skeletal dysplasia

polydactyly (always), rhizomelic shortening of limbs, cleft palate, cryptorchidism

VACTERL Association

V- vertebral anomalies

A- anorectal anomalies

C- cardiac anomalies

TE- tracheoesophageal fistula

R- radial ray anomalies

L- limb anomalies

CHARGE Association

C- coloboma

H- heart defects

A- atresia

R- retardation

G-genital hypoplasia

E- ear abnormalities