1. BIOCHEMICAL MARKERS OF PRENATAL DIAGNOSISBY
DR KHALED SALEH ALGERIRI
International Medicine School – MSU
November

2. Definition:
‘Prenatal diagnosis is defined as the detection of abnormalities in the fetus, before birth’
Without knowledge gained by prenatal diagnosis, there could be an untoward outcome for the fetus or the mother or both. Congenital anomalies account for 20 to 25% of perinatal deaths.

3. The objectives of prenatal diagnosis are
Managing the remaining weeks of the pregnancy
Determining the outcome of the pregnancy
Planning for possible complications with the birth process
Planning for problems that may occur in the newborn infant
Deciding whether to continue the pregnancy
Finding conditions that may affect future pregnancies

4. A- Biochemical assessment of MATERNAL health
Common problems in pregnancy include
1-gestational diabetes
Glucose screening tests at 24–28 weeks
2- Pre-eclampsia
Pre-eclampsia occurs typically in the third trimester and affects 4–8% of pregnancies
Urine protein (by dipstick testing or formal quantitation)
Serum uric acid
Renal function tests
Full blood count (for Hb concentration and platelet count)
In the absence of pre-existing pathology, these biochemical parameters should return to normal after delivery.

5. 1-Human Chorionic Gonadotropin
B- Biochemical assessment of PLACENTAL health
1-Human Chorionic Gonadotropin
The hormone human chorionic gonadotropin (better known as HCG) is produced during pregnancy. It is made by cells that form the placenta, which nourishes the egg after it has been fertilized and becomes attached to the uterine wall.
Levels can first be detected by a blood test about 8 days and about days after implantation by a urine test.
In general the HCG levels will double every 72 hours. The level will reach its peak in the first 8 – 11 weeks of pregnancy and then will decline and level off for the remainder of the pregnancy.

6. Guideline to HCG levels during pregnancy/ LMP Last menstrual period
3 weeks LMP: 5 – 50 mIU/ml
4 weeks LMP: 5 – 426 mIU/ml
5 weeks LMP: 180 – 7,340 mIU/ml
6 weeks LMP: 1,080 – 56,500 mIU/ml
7 – 8 weeks LMP: 7, 650 – 229,000 mIU/ml
9 – 12 weeks LMP: 25,700 – 288,000 mIU/ml
13 – 16 weeks LMP: 13,300 – 254,000 mIU/ml
17 – 24 weeks LMP: 4,060 – 165,400 mIU/ml
25 – 40 weeks LMP: 3,640 – 117,000 mIU/ml
Non-pregnant females: <5.0 mIU/ml

8. There are two common types of HCG tests
There are two common types of HCG tests. A qualitative HCG test detects if HCG is present in the urine . A quantitative HCG test measures the amount of HCG actually present in the blood.

9. What can a high HCG level mean?
A high level of HCG can also mean a number of things such as
1-miscalculation of pregnancy dating, so it should be rechecked within hours to evaluate changes in the level.
markedly elevated serum HCG suggests the presence of multiple pregnancies, especially with assisted fertilization, or the presence of gestational trophoblastic disease including chorionic carcinoma and hydatidiform mole

10. 2- Molar pregnancy (hydatidiform mole)
It is a noncancerous (benign) tumor that develops in the uterus. A molar pregnancy starts when an egg is fertilized, but instead of a normal, viable pregnancy resulting, the placenta develops into an abnormal mass of cysts. Molar pregnancies are rare, occurring in 1 out of every 1,000 pregnancies
Choriocarcinoma is a malignant, trophoblastic cancer, usually of the placenta. Choriocarcinomas may also occur after an early pregnancy that does not continue (miscarriage), or after an ectopic pregnancy or genital tumor.

11. Later in pregnancy, in the middle to late second trimester, the HCG can be used in conjunction with the AFP to screen for chromosomal abnormalities, and Down syndrome in particular.
An elevated -HCG coupled with a decreased AFP suggests Down syndrome.
Very high levels of HCG suggest trophoblastic disease (molar pregnancy).
The absence of a fetus on ultrasonography along with an elevated HCG suggests a hydatidiform mole.
The HCG level can be used to follow up treatment for molar pregnancy to make sure that no trophoblastic disease, such as a choriocarcinoma, persists.

12. Can anything interfere with my HCG levels?
Nothing should interfere with an HCG level except medications that contain HCG. These medications are often used in fertility treatments.
All other medications such as antibiotics, pain relievers, contraception or other hormone medications should not have any effect on a test that measures HCG.

13. C- Biochemical assessment of FETAL health
1-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

14. For prenatal diagnosis, most amniocenteses are performed between 14 and 20 weeks gestation. However, an ultrasound examination always proceeds amniocentesis in order to determine gestational age, the position of the fetus and placenta, and determine if enough amniotic fluid is present.
Within the amniotic fluid are fetal cells (mostly derived from fetal skin) which can be grown in culture for chromosome analysis, biochemical analysis, and molecular biologic analysis.

15. 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.
This is because the lungs are not producing enough surfactant. After birth, the infant will develop respiratory distress syndrome from hyaline membrane disease.

16. 2-Human chorionic gonadotropin (HCG) 3- Alpha-fetoprotein (AFP)
C- Biochemical assessment of FETAL health
2-Human chorionic gonadotropin (HCG) 3- Alpha-fetoprotein (AFP)
a protein synthesized by the fetus is detectable in maternal serum from week 6 of pregnancy, with a peak in week 34 of gestation (4 mg / ml), its value decreasing in 8-12 months after birth. Measurement of alpha-fetoprotein can be done from amniotic fluid or from maternal blood.

17. Elevated values of alpha-fetoprotein are found in:
Multiple pregnancies
Skin diseases;
Organ failure;
Congenital nephropathy;
Cystic higroma;
Hepatic necrosis;
Neural tube defects
Abdominal wall defects.

18. Low values of alpha-fetoprotein are recorded in cases
Chromosomal abnormalities
Defects of the placenta
Fetal hydrops
Trophoblastic disease
Diabetic mothers

19. Neural tube defects
NTD (Neural tube defects) can affect 1 in 500 infants
– Neural tube defects include anencephaly (failure of closure at the cranial end of the neural tube) and spina bifida (failure of closure at the caudal end of the neural tube).
– Neural tube beneath the backbone fails to develop definitive diagnosis relies on amniocentesis
– high levels of AFP seen in NTD

20. Neural tube defects can be distinguished from other fetal defects (such as abdominal wall defects) by use of the acetylcholinesterase test performed on amniotic fluid obtained by amniocentesis.
if the acetylcholinesterase is elevated along with AFP then a neural tube defect is likely.
If the acetylcholinesterase is not detectable, then some other fetal defect is suggested.

21. Down’s Syndrome – Down’s syndrome (DS) is a congenital disorder,
caused by a trisomy of chromosome 21
– risk increases with the mother’s age
The AFP can also be useful in screening for Down syndrome and other trisomies. The AFP tends to be lower when Down syndrome or other chromosomal abnormalities is present.

22. 4-Unconjugated Estriol
C- Biochemical assessment of FETAL health
4-Unconjugated Estriol
Estriol (E3) is one of the three major naturally occurring estrogens, the others being estradiol (E2) and estrone (E1).
In non-pregnant females, the major estrogen is estradiol produced by the ovaries.
During pregnancy, estriol is secreted by the placenta and fetus and becomes the dominant estrogen form.
The primary form of estriol measured during pregnancy is unconjugated estriol (also referred to as “free” estriol or uE3).
Maternal serum uE3 levels have been used as a functional marker of the fetal-placental unit and in the evaluation of pregnancy complications.

23. C- Biochemical assessment of FETAL health
5- Inhibin - A
Inhibins are glycoprotein hormones of which there are two molecular forms, inhibin A and inhibin B.
Classically, inhibin is known to have a negative feedback effect on pituitary follicle-stimulating hormone secretion.
Inhibin A is the predominant molecular form of inhibin in maternal circulation from 4 weeks of gestation.

24. The precise biological function of inhibin A in pregnancy is could be a better marker of placental function than human chorionic gonadotropin because of its shorter half-life.
The possible clinical applications for the measurement of inhibin A in early pregnancy could be in predicting miscarriage, Down's syndrome, preeclampsia, and fetal growth restriction in the first and/or second trimester before the onset of the clinical symptoms

25. 6- Pregnancy-associated plasma protein-A
C- Biochemical assessment of FETAL health
6- Pregnancy-associated plasma protein-A
This protein is thought to have several different functions, including preventing recognition of the fetus by the maternal immune system, matrix mineralization and angiogenesis.
Detection of this protein is also suggested as a first and second trimester diagnostic test for aneuploidies, including Trisomies 13, 18 and 21.
In addition, low PAPP-A levels in the first trimester may predict an adverse pregnancy outcome, including a small for gestational age (SGA) baby or stillbirth.
A high PAPP-A level may predict a large for gestational age (LGA) baby.

26. Prenatal Screening Modalities for fetal chromosomal anomalies
Quadruple maternal serum screening (Quad)
Maternal serum screening (Triple)
Combining the maternal serum assays may aid in increasing the sensitivity and specificity of detection for fetal abnormalities. The classic test is the triple screen for alpha-fetoprotein (AFP), serum HCG, and estriol (uE3). The "quadruple screen" adds inhibin-A

27. Biochemical markers in the second trimester
Condition
AFP
uE3
HCG
Inhibin A
Neural tube defect
Increased
Normal
Down’s syndrome
Decrease
Increase
Trisomy 18
Molar pregnancy
Very High
Multiple gestation
Fetal death (stillbirth)

28. THANK YOU