OB II Unit 3 Part 1

How many births have major congenital anomalies?

3 out of 100

What is the origin of chorionic villi?

fetal

obtaining fetal karyotype by the culturing of fetal cells

Chorionic Villus Sampling (CVS)

US directed biopsy of the placenta or chorion frondosum

Chorionic Villus Sampling (CVS)

Advantages of CVS

Performed early in pregnancy (10-14 weeks)

Results within 1 week

Earlier results allow parents more options

Embryoscopy

Direct viewing of embryo using a transcervical endosscope to detect fetal anomalies and aspirate blood samples for disorders

When is an embryoscopy done?

1st trimester

Where should the amniotic fluid pocket for an amniocentesis be located?

Near maternal midline - avoiding uterine vessels

Away from the fetus

Away from central portion of placenta

away from umbilical cord

fetal blood obtained by needle aspiration fo the umbilical cord

cordocentesisH

How long does it take for a cordocentesis karyotype to result?

2-3 days

What are the normal karyotypes?

46 chromosomes (22 autosome pairs - 2 sex )

What is the sex chromosome in karyotypes?

23rd 

presence of one or more extra chromosomes or the absence of one or more chromosomes

aneuploidy

Who is at risk for aneuploidy?

Anyone, but especially:

AMA, family history, abnormal screenings

What is the use of a triple/quad screen?

Identify pregnancies at risk for birth defects

What birth defects can be detected with a triple/quad screen?

aneuploidy

neural tube defects

GI defects

triple screen

blood screen evaluating: MSAFP, hCG, Estriol

quad screen

blood screen evaluating: MSAFP, hCG, Estriol, inhibin A

What does inhibin A improve?

detection rate for Trisomy 21

Trisomy 21 lab values

Low: AFP & estriol

High: hCG & inhibin A

Trisomy 18 lab values

Low: hCG, AFP, estriol, inhibin A

Trisomy 13 lab values

Low: hCg

High: Estriol

open neural tube defects or abdominal wall defects

High AFP

What are the screening tests for aneuploidy?

Quad Screen - AFP

Amniocentesis

What happens to the MSAFP lab value with gestational age?

increases with gestational age

causes of high MSAFP

incorrect dates, neural tube defects, demise, multiple pregnancy, molar pregnancy, chromosomal abnormalitieis

causes of low MSAFP

incorrect dates, missed abortion, chromosomal abnormalities

What lab value is the steroid of fetal origin?

estriol

What lab value is the protein produced by placenta and ovaries?

inhibin-A

What produces alpha and beta hCG?

synctiotrophoblast

What lab value is derived from trophoblastic tissues then diffused into maternal circulation? 

PAPP-A

levels of PAPP-A in correlation with pregnancy

Low in pregnancies with chromosomal abormalities

High throughout pregnancy

genetic abnormality with a strong association with maternal age

aneuploidy

most common genetic abnormality

Down Syndrome - Trisomy 21

physical features suggesting aneuploidy

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What is a targeted sonogram?

required when a specific abnormality or risk for abnormality is suspected

Patient being offered an amniocentesis?

•Which patient is offered an amniocentesis?

•2 or more sonographic markers &

•Maternal age < 35

•1 or more sonographic markers &

•Advanced maternal age (AMA)

soft markers

thickened nuchal fold in 2^nd trimester

absent/hypoplastic nasal bone

short humerus or femur

pyelactasis of 4mm or greater

hyperechoic bowel

echogenic intracardiac focus

choroid plexus cyst

genetic markers

polyhydramnios

2-vessel cord

straight umbilical cord

absent or hypoplastic nasal bone

absent or hypoplastic middle phalanx of 5th digit

clinodactyly

simian crease

sandal gap of the great toe

short ear length

abnormal pelvic angle

club feet

pyelectasis

enlargement of renal pelvis

> 4mm in 2nd trimester is abnormal

Choroid Plexus cyst and significance

controversy of the significance

Can be bilateral/unilateral, multiple/singular, and varied sizez

patient may be offered genetic counseling

reports of an association with Trisomy 18

Two-vessel cord associations

Oomphaloceles

cardiac defects

renal anomalies

two vessel cord views

free floating loop

cord insertion with arteries around bladder

Umbilical cyst in 2nd/3rd trimester association

Trisomy 18

Missing middle phalanx 5th digit association

Trisomy 21

permanent bend in one or more digits

clinodactyly - overlapping fingers

sandal gap foot

spread between 1st and 2nd digits

sandal gap foot association

Trisomy 21

talipes

club feet

Talipes association

neural tube defects

may be seen with: Trisomy 13, 18, & triploidy

Rocker bottom feet

absence of normal arch

Rocker bottom feet association

Trisomy 13 & 18

Cleft Lip Association

Trisomy 13 or 18

80% of trisomic fetuses had one or more of ….

hydramnios

congenital heart defect

diaphragmatic hernia/bowel defects

abnormal hands or feet

Who is benacerraf?

Discovered that 80% of trisomic fetuses have one or more of certain markers

endocardial cushion

embryonic tissue that forms the walls and valves of the heart

chromosomal abnormalities high yield

Cystic hygroma

duodenal atresia

oomphalocele/diaphragmatic hernia

holoprosencephaly, Dandy Walker