1st And 2nd Trimester Screening

Question 1

1st Trimester Screen (results of ea trisomy)

Answer 1

• 1st trimester - beta hCG and PAPP-A + nuchal translucency (10-13 wks)
• DS / trisomy 18 = dec both proteins by thicker translucency
• Trisomy 13 = dec PAPP-A

Question 2

2nd Trimester Screen (results for trisomies and neural tube defects)

Answer 2

• AFP, hCG, unconjugated estriol +/- inhibin A (15-21 wks)
• DS = dec AFP, dec unconjugated estriol, inc beta hCG and inc inhibin A
• Trisomy 18 = dec all
• Neural tube defects = inc AFP b/c opening not covered by skin so more gets into amniotic fluid and maternal blood

Question 3

What do you do if you have a positive screen?

Answer 3

• 1- check gestational age w/ US (also check for twins)
• 2- Amniocentesis - amniotic AFP and fetal karyotype
• 3- targeted US - look at fetal head and spine

Question 4

Reasons for Inc AFP (8)

Answer 4

• underestimating of gestational age
• neural tube defect
• ab wall defect
• cystic hygroma
• fetal skin defect
• sacrococygeus teratoma
• dec maternal wt
• oligophydramnios

Question 5

Reasons for Dec AFP (5)

Answer 5

• Overestimating of gestational age
• Chromo trisomy
• Molar pregnancy
• Fetal death
• Inc maternal wt