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
amniotic fluid 
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
Determine chorionicity/amnionicity
Dichorionic diamniotic twins
Most common type of twins
2 placentae
“Twin peak” if adjacent placentae
Thick separating membrane
Monochorionic diamniotic twins
Single placenta
No “twin peak” sign
Thin separating membrane
Twins are same gender
Monochorionic monoamniotic twins
