Neural Tube Defects

Question 1

Etiology of neural tube defects

Answer 1

1. folate deficiency
2. genetic (syndromes, trisomy 13 or 18)
3. racial predisposition (hispanics highest in US)
4. teratogenic exposure (maternal hyperthermia, fever/hot tubs)
5. obesity

Question 2

Prevalence in US NTD

Answer 2

• 2nd most common secondary to cardiac defects
• anencephaly (upper NTD 0.5/10,000 live births, 2.5/10,000 pregnancy)
• spina bifida (lower NTD 3.5/10,000 live births, 4.5/10,000 pregnancy)
• declining due to increased folate supplementation

Question 3

Failure of caudal end closure causes

Answer 3

• myelomeningocele
• and higher anatomical anomalies: hydrocephalus, decreased BPD (lemon sign and banana sign on US), Arnold chair malformation
• can require repeated ventricle-peritoneal shunts
• can cause neuro dysfunction, decreased IQ, impaired bladder and subsequent renal dysfunction, bowel dysfunction, ambulation impairment

Question 4

NTD suppression with folate

Answer 4

• standard dose 400 ug/day
• high risk pts 4000 ug/day
• given one month prepregnancy thru 12w
• 30% NTD will not be affected by folate supplementation due to genetic anomalies, obesity, hyperthermia, poor glucose control

Question 5

msAFP

Answer 5

• screens for NTD
• false positive rate 2%: associated with incorrect dating, other congenital anomalies
• false negative: associated with closed NTD (thin layer of skin covers defect

Question 6

diagnose NTD

Answer 6

• screening with msAFP
• US @18-20w
• by local defect finding or lemon sign and banana sign

Question 7

Mode of delivery for NTD

Answer 7

• due to standard obstetric conditions
• early term or late preterm if fetal surgery performed (due to tranmyometrial scar)
• uterine surgery is associated with increased functional ability, but requires two hysterotomies (1 for fetal repair, 1 for delivery), is associated with PTD, oligo, scar dehiscence