This document discusses various prenatal diagnostic techniques and preimplantation genetic diagnosis (PGD). It describes ultrasonography, amniocentesis, chorionic villus sampling, tests of maternal serum markers like beta-HCG, and PGD. Amniocentesis involves inserting a needle into the amniotic sac while CVS samples placental chorionic villi. Ultrasonography is non-invasive while amniocentesis and CVS carry small risks of miscarriage and preterm labor. PGD screens embryos before implantation to identify genetic defects and select only healthy embryos for transfer.

1. PRENATAL DIAGNOSIS
& PGD
Dr. Shazia Iqbal
Assistant Professor (Obstetrics &
Gynaecology)
Director of Medical Education Unit
Vision College of Medicine, Riyadh

2. OUTLINE
 Benefit.
 Techniques.
 Ultrasonography
 Amniocentesis
 Chorionic villus sampling
 Maternal serum beta-HCG
 preimplantation genetic diagnosis

3. BENEFIT
 Benefits Congenital abnormalities affect approximately 2% of newborn
babies in the UK
 Account for around 21% of perinatal and infant deaths, as well as causing
significant disability and morbidity later in life.
 There are a variety of non-invasive and invasive techniques available for
prenatal diagnosis.
 Each of them can be applied only during specific time periods during the
pregnancy for greatest utility.

4. THE TECHNIQUES EMPLOYED
FOR PRENATAL DIAGNOSIS
 Ultrasonography
 Amniocentesis
 Chorionic villus sampling
 Fetal blood cells in maternal blood
 Maternal serum alpha-fetoprotein
 Maternal serum beta-HCG
 Maternal serum unconjugated estriol

5. ULTRASONOGRAPHY
 This is a non-invasive procedure that is harmless to both the fetus and
the mother.
 High frequency sound waves are utilized to produce visible images from
the pattern of the echos made by different tissues and organs, including the
baby in the amniotic cavity.
 Recognition of the major internal organs and extremities to determine if
any are abnormal can best be accomplished between 16 to 20 weeks
gestation.

6. AMNIOCENTESIS
This is an invasive procedure in which a needle is passed through the
mother's lower abdomen into the amniotic cavity inside the uterus. Enough
amniotic fluid is present for this to be accomplished starting about 14 weeks
gestation. For prenatal diagnosis, most amniocenteses are performed
between 14 and 20 weeks gestation.
In the third trimester of pregnancy, the amniotic fluid can be analyzed for
determination of fetal lung maturity. This is important when the fetus is below
35 to 36 weeks gestation, because the lungs may not be mature enough to
sustain life following birth.
⮚Risks with amniocentesis are uncommon.
⮚Bleeding, cramping, and leaking fluid from the vagina
⮚Infection

7. CHORIONIC VILLUS SAMPLING
(CVS)
 In this procedure, a catheter is passed via the vagina through the cervix
and into the uterus to the developing placenta under ultrasound guidance.
An alternative approach is transabdominal.
 The introduction of the catheter allows sampling of cells from the placental
chorionic villi.
 These cells can then be analyzed by a variety of techniques. The most
common test employed on cells obtained by CVS is chromosome analysis
to determine the karyotype of the fetus.
 The cells can also be grown in culture for biochemical or molecular biologic
analysis.
 CVS can be safely performed between 9.5 and 12.5 weeks gestation.
⮚Risks of the procedure
⮚Miscarriage
⮚Preterm labor

8. CHORIONIC VILLUS SAMPLING
(CVS)

9. MATERNAL SERUM BETA-HCG
This test is most commonly used as a test for pregnancy. Beginning about a
week following conception and implantation of the developing embryo into
the uterus, by the time the first menstrual period is missed, the beta-HCG will
virtually always be elevated enough in maternal urine to provide a positive
pregnancy test. The beta-HCG can also be quantified in serum from
maternal blood, and this can be useful early in pregnancy when threatened
abortion or ectopic pregnancy is suspected, because the amount of beta-
HCG will be lower than expected.
Later in pregnancy, in the middle to late second trimester, the beta-HCG can
be used in conjunction with the MSAFP to screen for chromosomal
abnormalities, and Down syndrome in particular. An elevated beta-HCG
coupled with a decreased MSAFP suggests Down syndrome.
Very high levels of HCG suggest trophoblastic disease (molar pregnancy).

11. PREIMPLANTATION GENETIC
DIAGNOSIS

12. WHAT IS PGD
The procedure which involves the removal of one or more blastomeres to
test for mutations in a specific gene sequence or chromosomal abnomlalities
before transferring

14. PGD INDICATIONS
 An altemative to conventional PND for couples with a significant risk of
transmitting a serious genetic disorder to their offspring
 Avoiding abortion (enomaous physical and psycological burden)
 Presence of ethical concems in aborting embryoes affcted with specific
disorders ( for example: hearing oss, skeletal disorders, . . .)

15. CLINICAL APPLICATIONS
 Carriers ofmutations (Autosomal dominant disorders, Autosomal recessive
disorders)
 Female carriers of X- linked disorders
 HLA matching
 Carriers ofa balanced chromosomal trans[ocation, inversion or other
structural rearrangements

16. PGD PROCEDURE
 Stimulation : controlled ovarian stimulation
 Retrieval : oocyte retrieval
 Fertilization : fertilization (standard IVF/ICSI)

17. BIOPSY METHODS
In looking at the entire set of data, the most common method of zona
breaching used was laser drilling 58%
cleavage stage biopsy has predominated data collections I X.

18. WHY IS PGD NECESSARY
 the aim of PGD is to prevent transmitting genetic disorder to offspring
 Theses could include:
 Cystic Fibrosis (affects the lungs pancreas liver and intestine)
 Triploidy ((three) copies of each chromosome)
 Thalassemia (causes weakening and destruction of red blood cells
 Duchenne Muscular Dystrophy (causes muscle degeneration

19. HOW IS PGD PERFORMED
 During the PGD procedure in vitro embryos are
screened for genetic defects.
 only the healthy embryos that are considered
condition free are transferred for implantation

20. HOW IS PGD PERFORMED
 the procedure of PGD begins with IVF treatment later followed by genetic
screening:
1- During IVF eggs are harvested and fertilised by sperm in the laboratory to
form zygotes
2- the zygotes continue developing in the lab for about 3 days until they
typically reach the 8 cell stage
3- at this known as embryo biopsy is performed where an embryo’s cell is
extracted
4- the cell undergoes genetic screening where is analysed

22. How safe is PGD
The PGD treatment it self is thought to be very safe- there is no evidence
that babies born following PGD suffer any more health or developmental
problems than babies born using IVF alone. there are risk from having IVf
though

23. Why might PGD be unsuccessful
 Unfortunately sometimes there are embryo suitable for transfer to the
womb this could be because:
 Not enough eggs are produced or fertilised in the first place
 Removing the cell for analyses damages the embryos are affected by the
genetic disease

25. REFERENCE
⮚https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/chorionic-villus-
sampling-cvs
⮚https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5548328/
⮚https://webpath.med.utah.edu/TUTORIAL/PRENATAL/PRENATAL.html

26. THANK YOU