Screening program Flashcards

Question

At the foetal anomaly scan which indicators in low risk woman warrant further investigation?

Answer 1

Nuchal fold (>6mm) Ventriculomegaly (atrium >10mm) Echogenic bowel (with bowel density equivalent to bone) Renal pelvic dilation (>7mm) Small measurements Vs dating scan (<5th centile)

Answer 2

CVS from 10 weeks, usually 11 - 14 weeks. 10-25mg | AF from 15 weeks onwards 10-20ml

Answer 3

1-2% CVS, 0.5-1% AF.

Answer 4

18+ weeks. 2-2.5%

Answer 5

PAPP-A is a large zinc glycoprotein produced by the placenta where it is thought to regulate the activity of factors responsible for the growth of the placenta. Low levels in maternal blood in the first trimester are associated with pregnancies affected by Down’s, Edwards’ and Patau’s syndromes.

Answer 6

hCG glycoprotein produced by the developing embryo and later by the placenta.dimeric molecule composed -alpha and a beta subunit. The alpha subunit is common to several other hormones [luteinising hormone (LH), follicle stimulating hormone (FSH) and thyroid stimulating hormone (TSH)]. The beta subunit is unique to hCG. Concentrations of hCG rise exponentially after conception reaching a peak at about 9-12 weeks, then falling to reach a plateau at about 20 weeks. Some of the beta subunit (less than 1% of the intact dimeric hCG) is free in the blood and this molecule can be measured by the laboratory as a distinct entity. A raised level of hCG and/or the free beta subunit in the first and second trimester is associated with an increased chance of a Down’s syndrome affected pregnancy. A decreased level is associated with both Edwards’ and Patau’s syndromes.

Answer 7

AFP is a glycoprotein of 591 amino acids produced by the yolk sac and the fetal liver. Its level in fetal serum increases until the end of the first trimester and then gradually decreases. Concentrations are much lower in maternal serum but they continue to rise until about week 32. An increased level in maternal serum is associated with a possible neural tube defect such as spina bifida, although ultrasound scanning is the recommended screening test for neural tube defects. Decreased levels in the second trimester are associated with Down’s and Edwards’ syndromes

Answer 8

Oestriol is one of the three main steroid hormones produced by the feto-placental unit during pregnancy. It is made in the placenta from the 16-hydroxydehydroepiandrosterone produced by the fetal liver. Once in the maternal circulation most of the oestriol undergoes conjugation with glucuronides or sulphate but about 10% remains as the unconjugated form. Low levels of uE3 in the maternal circulation in the second trimester are associated with Down’s and Edwards’ syndromes.

Answer 9

Inhibin-A is a dimeric molecule comprised of an alpha and a beta polypeptide chain linked by a disulphide bridge. (A similar molecule called Inhibin-B has the same alpha chain but a different beta chain). It is produced by the corpus luteum and the placenta during pregnancy with levels increasing during the first trimester, then declining to reach a plateau in the second trimester before increasing again in the third trimester. Elevated levels in the second trimester are associated with pregnancies affected by Down’s syndrome.

Answer 10

T21 and T18 / T13 T21 only T18 / T13 only not to have screening