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In The Name Of God

In The Name Of God. Serum Biochemistry. Vajiheh Marsoosi, M.D Associate Professor of TUMS Shariati Hospital. Serum Biochemistry. Trisomic Pregnancies are associated with altered maternal serum concentration of various feto -placental products.

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In The Name Of God

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  1. In The Name Of God

  2. Serum Biochemistry Vajiheh Marsoosi, M.D Associate Professor of TUMS Shariati Hospital

  3. Serum Biochemistry • Trisomic Pregnancies are associated with altered maternal serum concentration of various feto-placental products. • Screening in the first trimester by a combination of maternal age, fetal NT, and serum free ß-hCG and PAPP-A identifies about 90% of trisomy 21 pregnancies for a false positive rate of 3%.

  4. Serm Biochemistry In trisomy 21 pregnancies maternal serum free ß-hCG is about twice as high and PAPP-A is reduced to about half compared to chromosomally normal pregnancies.

  5. Serum Biochemistry • Adjustment is necessary in the measured free ß-hCG and PAPP-A • Each measured level is first converted to a multiple of the expected normal medium (MoM) specific to the same gestation, maternal weight, smoking status, ethnicity and method of conception.

  6. Serum Biochemistry • In Black women the PAPP-A level is about 60% higher than in White women. • In women who smoke and those conceiving by IVF serum PAPP-A is decreased and this could increase in false positive rates.

  7. Serum Biochemistry In trisomy 21 pregnancies: • Free ß-hCG is higher than in euploid pregnancies and the difference between the two is higher at 13 than at 11 weeks. • Serum PAPP-A is lower than in euploid pregnancies and the difference the two is higher at 11 than at 13 weeks. • The difference from euploid pregnancies in PAPP-A at 11 weeks is greater than the difference in ß-hCG at 13 weeks and therefore the overall performance of biochemical markers is better at 11 than at 13 weeks.

  8. Combined Screening In trisomy 21compared to euploid pregnancies: • The difference in biochemical markers is greater at 11 than at 13 weeks. • The difference in fetal NT is greater at 11 than at 13 weeks. • Therefore the overall performance of screening is better at 11 than at 13 weeks.

  9. Combined Screening The overall performance of combined screening is better at 11 than at 13 weeks and may be best at 10 weeks. • Ultrasound screening for fetal abnormalities is better at 12 than at 11 weeks and much better than at 10 weeks. • A good way of achieving a high performance of screening for trisomy 21 and diagnosing major fetal defects by ultrasound is to carry out the blood test at 10 or 11 weeks and the ultrasound scan at 12 weeks.

  10. Combined Screening Other defects In euploid pregnancies the average free ß-hCG is 1.0 MoM and PAPP-A is 1.0 MoM In chromosomal defects the values are: free ß-hCG PAPP-A Trisomy 21 2.0 0.5 Trisomy 18 0.2 0.2 Trisomy 13 0.3 0.4 Turner 1.2 0.5 Triploidy Digenic 0.2 0.1 Diandric 9.0 0.7

  11. Combined Screening Other defects • There are differences between the three trisomies: • Fetal NT is higher in T18 and T 13 than T21 • Serum free ß-hCG in trisomy 21 is high whereas in trisomies18 and 13 this is low • Serum PAPP-A is lower in trisomies18 than in trisomy 21 • Fetal heart rate in trisomy 13, unlike trisomies 21 and 18, is high

  12. Thank You

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