Periconceptional Folate Deficiency and Implications in Neural Tube Defects

Table 1

Proven and suspected risk factors for spina bifida (NP = not proven).

Risk factors: proven and certain	Relative risk
History of NTD-affected pregnancy	30
Valproic acid and carbamazepine	10–20
Pregestational maternal diabetes	2–10
Inappropriate/deficient folic acid supplementation	2–8
Paternal exposure to dioxins in Agent Orange [42]	2
Risk factors: suspected	Relative risk
Maternal vitamin B12 status	3
Maternal diarrhea	3-4
Maternal obesity	1.5–3.5
Maternal hyperthermia	2
Nonproven (NP) risk factors, with epidemiological associations	Relative risk
Gestational diabetes	NP
Pesticides	NP
Herbicides	NP
Fumonisins	NP
Water chlorination	NP
Heavy metals: lead	NP
Organic solvents	NP
Plastic byproducts (vinyl chloride, PVC)	NP
Toxic waste sights	NP
Electromagnetic field	NP
Retinoic acid (vitamin A) excess [48, 49]	NP