Elevated Msafp

Elevated Msafp
Roya Sohaey, MD
DIFFERENTIAL DIAGNOSIS
Common
  • Open Neural Tube Defect
    • Spina Bifida
    • Exencephaly, Anencephaly
    • Encephalocele
  • Abdominal Wall Defect
    • Gastroschisis
    • Omphalocele
    • Body Stalk Anomaly
  • Multiple Gestations
Less Common
  • Perigestational Hemorrhage
  • Fetal Demise
  • Placental Insufficiency
Rare but Important
  • Maternal Tumors
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
  • Alpha fetoprotein (AFP)
    • Normally produced from several sources in developing fetus
      • Yolk sac
      • Fetal gastrointestinal tract
      • Fetal liver
    • Circulation of AFP
      • Fetus image amniotic fluid image maternal serum
  • Maternal serum alpha fetoprotein (MSAFP) test
    • Drawn at 15-20 weeks menstrual age
      • Part of genetic screening
      • Screening for anomalies (spina bifida)
    • Adjusted for maternal factors
      • Weight
      • ± Diabetes
      • Ethnicity
    • MSAFP results
      • Reported as multiples of the median (MOM)
      • > 2-2.5 MOM considered positive screen
  • Reasons for positive MSAFP screen results
    • Incorrect menstrual dates (20%)
      • Recalculate result after ultrasound
    • Unsuspected multiple gestations
      • Twin MSAFP = approximately twice singleton values
      • Use of MSAFP screening in known multiple gestation is controversial
    • Fetal anomalies
      • Any anomaly with ↑ fetal internal organ exposure to amniotic fluid
    • Placental abnormalities
      • Primarily from fetal-placental hemorrhage
      • Fetal levels 100,000 times > maternal
      • Small hemorrhage easily causes ↑ MSAFP
Helpful Clues for Common Diagnoses
  • Open Neural Tube Defect
    • Spina Bifida
      • Bony vertebral defect + neural content exposure to amniotic fluid
      • 73% lumbar
      • 17% sacral
      • 9% thoracic
      • 1% cervical
      • 80% with overlying sac
      • Almost all with Chiari II malformation of brain
      • 14% with aneuploidy
    • Exencephaly, Anencephaly
      • Absent calvarial vault
      • Variable amount of supratentorial brain
      • Brain exposed to amniotic fluid, which erodes neural tissue and leaves angiomatous stroma
      • Face: Proptotic eyes, cleft lip/palate
    • Encephalocele
      • Herniation of intracranial structures through skull defect
      • Occipital most common
      • Parietal, vertex, frontal more rare
      • Associations: Trisomy 13, trisomy 18, Meckel-Gruber syndrome
      • Look carefully for other anomalies
  • Abdominal Wall Defect
    • Gastroschisis
      • Bowel herniation through right paramedian defect
      • Normal cord insertion
      • No covering membrane
      • Progressive bowel dilatation often seen
      • Intrauterine growth restriction (IUGR) common in 3rd trimester
      • Almost all with ↑ MSAFP
    • Omphalocele
      • Herniation of abdominal contents into base of umbilical cord
      • Midline abdominal wall defect
      • Most often involves liver
      • Covering membrane present (difficult to see early, without ascites)
      • 70% with ↑ MSAFP (30% normal MSAFP)
      • 30% with aneuploidy
      • Omphaloceles that contain only bowel more associated with aneuploidy
    • Body Stalk Anomaly
      • Fetal evisceration
      • Visceral organs attached to placenta
      • Short or absent umbilical cord
      • No covering membrane
      • Scoliosis is prominent feature
      • Amniotic bands seen in 40%
    • Other abdominal wall defect diagnoses
      • Pentalogy of Cantrell
      • OEIS syndrome
      • Bladder/cloacal exstrophy
  • Multiple Gestations
Aug 10, 2016 | Posted by in OBSTETRICS | Comments Off on Elevated Msafp

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