Congenital Abnormalities and their identification

Question 1

What % of pregnancies are affected by congenital abnormalities?

Answer 1

2%

Question 2

What are the types of congenital abnormalities and their identification?

Answer 2

Structural deformities - diaphragmatic hernia

Chromosomal abnormalities - Down’s syndrome

Inherited disease - cystic fibrosis

Intrauterine infection - rubella

Drug exposure - anti-epileptics

Question 3

How can prenatal testing be done?

Answer 3

Chromosomal abnormalities - levels of several maternal blood markers

NIPT - free foetal DNA in maternal circulation allows non-invasive diagnosis of chromosomal abnormalities - tests take >1 week and are expensive

Question 4

What maternal blood markers can be checked for congenital abnormalities?

Answer 4

(combined test between 11 and 14 weeks)
B-hCG
pregnancy associated plasma protein A (PAPP-A)
Nuchal translucency

If the woman books late: quadruple test - bHCG,
Alpha fetoprotein (AFP)
estriol
inhibit A

Question 5

What is USS used for in pregnancy?

Answer 5

used to determine the gestation and pregnancy site and exclude multiple pregnancy

Nuchal translucency - measures the space between the skin and soft tissue overlying the cervical spine and the larger it is, the higher the risk.

Used to guide amniocentesis and CVS

Structural abnormalities - congenital malformations of all organs and systems are detectable.

Question 6

What is foetal MRI used for?

Answer 6

To aid diagnosis of intracranial lesions - better differentiate between different types of soft tissue

May also have a role as an alternative to post-mortem examination

Question 7

What does 3D or real-time 3D USS do?

Answer 7

Reconstruct 3D ultrasound image - allow better evaluation of certain abnormalities (being extensively used)

Question 8

What is amniocentesis

Answer 8

Diagnostic test involving the removal of amniotic fluid using a fine-gauge needle under USS guidance

Safest performed at 15 weeks - may be done later

Question 9

What is the purpose of amniocentesis?

Answer 9

enable pre-natal diagnosis of chromosomal abnormalities - some infections (CMV and toxoplasmosis) and some inherited disorders (sickle cell, thalassaemia and CF)

Question 10

What is the risk of amniocentesis?

Answer 10

1% women miscarry after amniocentesis - most unrelated to the procedure

Question 11

What is chorionic villus sampling?

Answer 11

Diagnostic test involving biopsy of the trophoblast by passing a fine gauge needle through abdominal wall (or cervix) into the placenta - from 11 weeks

Question 12

What is the advantage of CVS over amniocentesis?

Answer 12

Results can be obtained earlier than amniocentesis and allows abnormal foetus to be identified at time when abortion is usually performed under GA

Question 13

What risk is higher with CVS than amniocentesis?

Answer 13

miscarriage - but performed earlier when spontaneous miscarriage is more common

Question 14

What tests are done with CVS and amniocentesis?

Answer 14

FISH, karyotyping and micro-array CGH is used to identify chromosomal abnormalities

Question 15

In what circumstances can preimplantation genetic diagnosis be done?

Answer 15

in IVF - cells can be removed from a developing embryo for genetic analysis before it is transferred into the uterus - allows selection of only embryos that will not be affected by the disorder for which it is being tested

Question 16

What can preimplantation genetic diagnosis be used to detect?

Answer 16

sex-linked disorder, trisomies, autosomal dominant and recessive condition

Question 17

What is the the ‘combined test’

Answer 17

integrates the risk from maternal age, with PAPP-A and B-hCG blood tests, with nuchal translucency at dating scan - performance of test can be enhanced using other risk factors - e.g. absence of nasal bone and tricuspid regurgitation

Question 18

what are the indications of the quadruple test?

Answer 18

booking is too late for nuchal scan or it is technically not possible (BMI)

Question 19

What are the components of the quadruple test?

Answer 19

Blood test (14-22 weeks)
Free bHCG 
AFP
Inhibin A 
Oestriol