Monday, June 22, 2009

Prenatal Diagnosis

A 25 year old Caucasian woman (G1P0) with epilepsy presents to prenatal diagnosis clinic because a routine maternal serum AFP screen at 16 weeks showed a value 2.5 multiples of the median. An ultrasound confirms the diagnosis.

Challenge: To prevent this in the future, you would recommend that she take what drug? You would recommend that she stop what drug?

Image is in the public domain.

6 comments:

Anonymous said...

take folic acid, discontinue valproate?

Stephanie said...

neural tube defects 2/2 valproic acid...folate deficiency. take folate, avoid septra too!

Alex said...

valproate

Craig Chen said...

Yes! The US Preventative Services Task Force recently recommended all women of childbearing age take a daily folic acid supplement 0.4-0.8mg (seriously though, how many of my classmates take folate?).
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Prenatal Diagnosis

Neural tube defects are strongly associated with valproic acid use, consistent with the maternal history of seizures. MSAFP is a standard screening protocol and can be followed with sonographic imaging and amniocentesis for diagnosis. Folic acid supplementation prevents this disorder. Neural tube defects include spina bifida (cleft in the spinal column; occulta is usually not diagnosed, but meningocele and meningomyelocele can be diagnosed) and cranial defects such as anencephaly.

Source: UpToDate.

World of Science said...

The generally accepted guidelines for eligibility of pregnant women for prenatal diagnosis by amniocentesis or CVS are based on evidence that the risk that the fetus is abnormal is at least as great as the risk of miscarriage from the procedure itself.

Craig Chen said...

That is correct - for invasive prenatal diagnosis procedures, the risks must be weighed against the benefits. Historically, the age of 35 ("advanced maternal age") was chosen because the probability of iatrogenic miscarriage was equal to the probability of Down syndrome (approx 1%). However, most recently, the push has been less towards a definite cut-off and more to presenting the risks and benefits in a manner understandable to the patient.